I've got an SG 3-link on my Disco 1. I'm currently running 5in RTE springs. I'm looking to get the truck a touch lower, as soon as I find springs I like. Anyway...with the truck at this height, the links are at angles that I am not sure about. The center link is pretty steep, and the outers are not close to flat. I've been reading up on 3-link calcutators in General and am just curious what kind of angles and relationships I should be trying to achieve. 99% of what is out there has the center on top of the axle and the outers below, so the numbers confuse me a bit. I am new to fabricating, have always been a bolt on guy.

Or...am I over thinking this?

Thanks

Chad

Answers LOOONG. But, put the SG 3 link into the calculator. I am wondering what it spits out. I am guessing a well over 10 roll angle. I only want to know becaus of a thingy I am struggling with right now.

My outers are at 4deg. My center is at almost 20deg.

Here is the thread I'm fighting through now trying to learn more:

http://www.pirate4x4.com/forum/showthread.php?t=168577&highlight=link&page=4

And...does the orientation of the bar above center of the bolt on the lower end of the center link seem ok?

Measuring for numbers now, but I'm stumped on "sprung mass CG" Not sure how to figure my CG. Guess I have to read more...

http://www.jeepaholics.com/tech/cog/#_Toc535118705

I'm using this calculator:

http://www.pirate4x4.com/forum/showthread.php?t=204893

My brain may explode!

Measuring for numbers now, but I'm stumped on "sprung mass CG" Not sure how to figure my CG. Guess I have to read more...

http://www.jeepaholics.com/tech/cog/#_Toc535118705

I'm using this calculator:

http://www.pirate4x4.com/forum/showthread.php?t=204893

My brain may explode!

Don't let your brain explode! Bottom line, when all said and done. its just theory. Everyone makes sacrifices, and no set of rules is perfect for every situation. Use the bolt on the top of your transmission bell case for CG. It's close. This only affects Anti Squate, so it's not really a number that is all that important. Well it is, but I don't want to go into it again.

Your link mounted all wierd on that joint won't affect the numbers, and there is nothing wrong with it as long as the welds are good. Post up bud!

Is the calculator I posted the one to go with? I'm going to have to do some more reading in order to properly fill it out.


Also...it seems like most like to keep all 3 links parallel or close to it, and the lengths close to same. If you've seen my other brake thread, I think my brakes are fine. I'm leaning towards geometry issues up front.

In my experience which is for this purpose more "seat of the pants" than calculated....the 3 link works well with 3" lift springs which I think was the lift they were designed around. I've taken 5" springs off and run 3" springs with a 2" body lift (several times now) and had the whole drivetrain and suspension work so much better.

The picture makes it look like there is a ton of thread showing on the shank on the X member end heim. How far does the shank thread into the link on that end?

Is the calculator I posted the one to go with? I'm going to have to do some more reading in order to properly fill it out.


Also...it seems like most like to keep all 3 links parallel or close to it, and the lengths close to same. If you've seen my other brake thread, I think my brakes are fine. I'm leaning towards geometry issues up front.

They don't have to be. At all, but it all affects things how they interact. You want your lower (in your case) to be around 25% shorter than the uppers for pinion angle during travel. If they were equal the pinion would mirror the link during travel so everything would be moving all over the place. Not necessarily a bad thing, but I have seen it bend shocks. Your calculator is correct as long as your picking the 3link one.

OK so can we arrange a 'go to meeting' and have Buck ( If he is willing) explain all this to us. Cause I feel like an idiot looking at this. We can reacord it and post it on the forum as a sticky. Let me know if your willing Buck. I will arrange the meeting. Everyone whos interested PM me your email address.

The picture makes it look like there is a ton of thread showing on the shank on the X member end heim. How far does the shank thread into the link on that end?

There is still a couple of inches of thread inside the link. The local TeraFlex dealer said it was cool. It does look crazy though.

I'll finish measuring later. It started raining and I wasn't ae to finish. I'm lowering the truck soon, and will put those numbers in as well.

What's anti-squate?

What's anti-squate?

It's the opposite of pro-squate. :flipoff2:

stiggy, I'm no expert. There are people on this board like triage that have infinitely more knowledge than me. My info is just from research and somewhat limited experience. I've only set up links 4 times. I am fairly versed on the limitations that the rover frame has as to placement, and the downsides of the available systems.

Allright I will try to sucker someone else into it.

Stig...read the threads I linked. Great info, but a lot to wrap my head around as a rookie. Strange Rover does a really good job if explaining things.

Looks like I've got some Stage III springs inthe way, so I'll be throwing some new numbers at it soon.

I finally got the numbers ran. I can't get them to post though(zipped file). Doesn't really matter now since I have it apart doing the hydro steering, swivels, and new springs...unless someone just wants the numbers for future reference. I'll run new numbers when I get it lowered...

I finally got the numbers ran. I can't get them to post though(zipped file). Doesn't really matter now since I have it apart doing the hydro steering, swivels, and new springs...unless someone just wants the numbers for future reference. I'll run new numbers when I get it lowered...

I'd like to see them. Just the roll axis and anti squat.

I'd like to see them.

x2, since you already did the hard work, may as well just post them for future reference.

Also, it's been asked, but not answered, how much thread enguagment do you have on that center-link heim?

I'll post them when I get home tonight. They are on my comp at home. There is still at least 2in of thread inside.

Lets take bets on the roll axis number. Maybe a pool? Well put the over-under at 8. Who's in?

BBLB,
what is the verticle seperation at the axle?I am sure its just the camera angles, but it looks like its 4-5" :eek:

BBLB,
what is the verticle seperation at the axle?I am sure its just the camera angles, but it looks like its 4-5" :eek:

That looks okay to me. Hard to tell. I'm interested in the numbers because of how short and vertical the center link is as well as the vertical separation at the frame end. I bet it unloads like Peter North going up hill.

I bet it unoads like Peter North going up hill.

Now that's the funniest thing I've read all week:laughing:

regarding COG, i was talking to mate of mine who knows a bit about rovers..... he seemed to think the COG would be lower than the TOBH, we were going to tip my d110 over with his 7t john deere and calc it, but ran out of time my last trip out to his property. next time i go out i will try and do it........of coarse wheel track and lift height will change from rig to rig

Serg

OK...first sorry for the delay. I'm stuck using my iPhone for Internet right now, so I can't load the results.

Seccond...I need help understanding the calculator. My numbers are f-ed. My roll axis is like 28. I know that's due to user errror. I need help determining what goes where. For example...the calculator asks for two upper and two lower link values. What should I use for the other lower? What do the values mean? I made assumptions. I was off! In the spreadsheet it asks for center of axle to rear +. WTF?

Also, I have the Stage III springs on and it sits about 1.5 lower. I'll put those numbers in when I know what the hell I'm doing. Sorry for being a lame ass newbie!

Thanks

Chad

OK...first sorry for the delay. I'm stuck using my iPhone for Internet right now, so I can't load the results.

Seccond...I need help understanding the calculator. My numbers are f-ed. My roll axis is like 28. I know that's due to user errror. I need help determining what goes where. For example...the calculator asks for two upper and two lower link values. What should I use for the other lower? What do the values mean? I made assumptions. I was off! In the spreadsheet it asks for center of axle to rear +. WTF?

Also, I have the Stage III springs on and it sits about 1.5 lower. I'll put those numbers in when I know what the hell I'm doing. Sorry for being a lame ass newbie!

ThanksChad

Find the 3 link calculator, your using the 4 link. You can search for Triage and find it. The center of axle measurement is for the link mount on the axle. For instance, if the bolt hole on the tab is 3in away from the axle toword the frame, it would be +3. Or if your top link it 2 inches ahead of the axle center line, it would be -2.

I have to do a lot of work tonight on the computer. If you want, and can stay online, we can go through things and I can put the data into the calculator for you.

I am actually really interested in this. I think I have an idea for a 3 link for a rover that can solve what I *think* the SG 3 link lacks in. The numbers will tell me if my theories are right. Or probably way wrong.

Buck,

I'm on the iPhone until about midnight central time. (it's 11:08 now) I can get on a real connection then.

Chad

Buck,

I'm on the iPhone until about midnight central time. (it's 11:08 now) I can get on a real connection then.

Chad

I think I can swing that. Well run through it. Might be informative for the masses (stig, may he not kill people).

I can't get the file uploaded. I've tried as a word document, spreadsheet, etc... Anyway, it's the 3link calculator by Triaged. It asks for upper, lower, and panhard values. Frame and axle end for all three. X, Y, Z for all three.

X-forward from rear axle centerline
y-distance from axle centerline +left,half of lower link horizontal seperation to frame, distance from axle centerline (u,l,p respectively)
z-height from ground

Chad

I can't get the file uploaded. I've tried as a word document, spreadsheet, etc... Anyway, it's the 3link calculator by Triaged. It asks for upper, lower, and panhard values. Frame and axle end for all three. X, Y, Z for all three.

X-forward from rear axle centerline
y-distance from axle centerline +left,half of lower link horizontal seperation to frame, distance from axle centerline (u,l,p respectively)
z-height from ground

Chad

If you just post your measurements, I can get it all in the calculator and post the numbers. Not tonight though, tired.

That's the problemo, I don't know what to measure to represent the values it wants. I don't know what x,y, and z are.



Upper Link x y z
Frame End 20.00 -4.00 15.75
Axle End 0.00 -4.00 18.00
Lower Links x y z
Frame End 23.98 24.00 7.50
Axle End -2.00 24.00 7.50
Pannhard Bar x y z
Frame End -8.00 -24.00 13.00
Axle End -8.00 24.00 13.00

(these are NOT my numbers)

That's the problemo, I don't know what to measure to represent the values it wants. I don't know what x,y, and z are.



Upper Link x y z
Frame End 20.00 -4.00 15.75
Axle End 0.00 -4.00 18.00
Lower Links x y z
Frame End 23.98 24.00 7.50
Axle End -2.00 24.00 7.50
Pannhard Bar x y z
Frame End -8.00 -24.00 13.00
Axle End -8.00 24.00 13.00

(these are NOT my numbers)

X upper link is foreword from axle centerline. The lenth of the upper link. Measure from the bolt on the frame of the upper link (IN YOUR CASE LOWER LINK) to the center of the axle tube.

Y is distance from axle centerline positive to the left. So the offset of the bracket from one side to the other. I think yours is centered so it would be zero.

Z Height from ground.

Repeat these for the frame end of the lower link.

That should get you started. For the lower links (IN YOUR CASE UPPER LINKS) do the same except Y is now half the distance between the two mounts on the axle, and then below it on the frame.

Panhard is pretty simple.

You good??

That should get me started, thanks. It's pouring rain right now, so it'll be a few...

The 3 link spreadsheet assumes a conventional 3 link plus panhard rear suspension.

It works for front suspensions and AFAIK will work for Safarigard type 3 links if you adjust your thinking so that you enter the input data properly.

For rear suspension, the rear axle should be at left and front to right.

For front suspension, the front axle should be at left and rear to right.

'Conventional' 3 link plus panhard rear suspension has 1 upper link and 2 lower links. The lower links are equal distance either side of vehicle centerline - because of this symmetry it is only necessary to enter data for one of the 2 lower links.

'Safarigard' type 3 link has 2 upper and 1 lower links.
I expect (but haven't checked), as Buck stated, you should enter measurements for your actual upper links into the spreadsheet cells for 'lower links', and enter measurements of your actual lower link into the spreadsheet cells for 'upper link'.

However you can also try it the other way and compare the results. Once you have the measurements, it should only take a few minutes to change and it won't do any damage.

In the 3 link spreadsheet:

worksheet named 'Coordinate' has a diagram (see pic below) that shows where the 'X', 'Y', and 'Z' measurements are taken from.

X is horizontal dimension, measured from axle center to the center of the link pivots/joints/bolts. The 'red' arrow on the diagram points to the +ve direction, i.e. +ve if to right of axle, -ve if to left of axle.
Y is horizontal dimension from centerline of vehicle to the center of the link pivots. The 'green' arrow points to the +ve direction.
Z is the vertical dimension from the ground. 'Blue' arrow points to the +ve direction.

worksheet named 'Main' is where you enter input data. The diagram is a plot of the link geometry that you enter. It shows:

upper link as 'blue' line
lower links as 'red' lines
panhard link as 'yellow' line



Edit: I just did a quick check with some dummy measurement pulled out of the air and the above comments for Safarigard type 3 link appear to work ok, i.e. enter measurements for actual lower link in cells for upper link (blue link) and enter measurements for actual upper links in cells for lower links (red links).

Ok, so this is a major rookie question, but why did safari guard, and most everyone else on rovers, do their 3 link upside down from most other applications? Was it clearance issues on the axles, or the frames, or neither?

Ok, so this is a major rookie question, but why did safari guard, and most everyone else on rovers, do their 3 link upside down from most other applications? Was it clearance issues on the axles, or the frames, or neither?

There is no upside down or right side up. There is common and uncommon. SG did it that way because of clearance issues. Although I would also wager that he didn't know much about link geometry at all. But back then, knowledge wasn't as available as it is now.

There is no upside down or right side up. There is common and uncommon. SG did it that way because of clearance issues. Although I would also wager that he didn't know much about link geometry at all. But back then, knowledge wasn't as available as it is now.

I was afraid I was going to get a response like that. Poor wording on my part... So was sg's clearance issue on the axle, or was it frame related? I know there is not right and wrong, and I am a firm believer in that motto, but there is usually a difficult and a "more" difficult. I am wondering for a rover application, which is which... If I were to run a different axle would it be "less" difficult to run the two links on bottom, or the top?

I was afraid I was going to get a response like that. Poor wording on my part... So was sg's clearance issue on the axle, or was it frame related? I know there is not right and wrong, and I am a firm believer in that motto, but there is usually a difficult and a "more" difficult. I am wondering for a rover application, which is which... If I were to run a different axle would it be "less" difficult to run the two links on bottom, or the top?

It's been so long since I had a stock rover that answering that question is hard for me. I think he wanted to make it all bolt-on, which complicates the task majorly. I couldn't figure out how to make mine bolt on without serious mental juice. Also the tie rod is simply very pesky being back there. I want someone to drop off their rig to me and let me make one. I have an idier. :eek:

I can live with that answer. I wish I lived a little closer, I am in design/planning mode right now, and am always open for suggestions! Or better yet let someone with more experience or knowledge than me do it for me!!!

I can live with that answer. I wish I lived a little closer, I am in design/planning mode right now, and am always open for suggestions! Or better yet let someone with more experience or knowledge than me do it for me!!!

Start a thread and post up tons of pictures and measurments and I can walk you through how I think it can be done. My rover is so far gone at this point that nothing remains for me to take any measurments off of other than a half curve in the frame.

OK, here's what I got:

Center of axle to forward pivot center, center link: 10in
Center of axle to forward pivot center, upper links: 4in
Length of center link (bolt center to bolt center): 18in
Length of upper links (bolt center to bolt center): 29in
Height of center link (forward to rear): 14in to 19in
Height of upper links (forward to rear): 20in to 21in
Height of axle center: 16.5in
Wheelbase: 100in
Distance from center of axle to upper link pivots: 17.5in
Center link is off-set from center 1.25in to driver at forward pivot(don't know why).
Center link is off-set from center 0in at rear pivot.

I'm going to try and put this into the calculator now...

I have no clue how to get this spreadsheet to post here. But, here's what I got:

Anti squat: 228.3
Roll axis: 15.52
Roll center: 21.42

I have no clue how to get this spreadsheet to post here. But, here's what I got:

Anti squat: 228.3
Roll axis: 15.52
Roll center: 21.42

Okay,

I put all your data in and got the same anti squate but only a 2 degree of roll axis. Something is seriously off. On mine I think too. First off, the cog HAS to be wrong. If you had a 230 antisquat, everytime you hit the brakes, the front end would unload, like all the way. Also, if it had a 15 roll axis it would feel like your going to roll around every corner. But a 2 degree roll axis like I got seems exremely unlikely. I would have thought it would be through the roof. But, if it is still dependent on the 2 links planes then it is possible.

Wait, holy hell. You might have the updated calculator. I just messed with the calculator and if you move the antisquate plane to the upper link (lower in yours) then you do get the 15 degrees. That makes sense, but if all this is true, thats got to drive like monkey ass.

It actually drives ok. It's the braking I'm trying to get improved. It pulls left pretty hard. Problem is, it doesn't always do it. It tracks well, steers good, no bump steer, etc... I guestimated the COG. Assuming it does drive like monkey ass...suggestions? Longer uppers, relocate center link pivot closer to axle, longer center, ???

It actually drives ok. It's the braking I'm trying to get improved. It pulls left pretty hard. Problem is, it doesn't always do it. It tracks well, steers good, no bump steer, etc... I guestimated the COG. Assuming it does drive like monkey ass...suggestions? Longer uppers, relocate center link pivot closer to axle, longer center, ???

Let me noodle.

Pulling to left is not the links.

Does the front end lift while braking? If those numbers are right, it should be near scary to drive. You can mask a lot with springs and shocks though.

It seriously drives pretty good. I can do 70+ with a finger on the wheel. It tracks well. Steers good. It's great on side roads. The only real issue is the pulling when braking. I've thrown every part at it in the book. The only thing I haven't changed is the booster. Every other brake component is brand spankin new. This whole exercise began because of the brakes.

I just re-entered the data using the lower as upper and upper as lower. The graph now represents my set-up better. I also moved the COG. 26 seemed low. The new numbers are:

Anti squat: 164.94
Roll axis: 1.97
Roll center: 19.96

I just re-entered the data using the lower as upper and upper as lower. The graph now represents my set-up better. I also moved the COG. 26 seemed low. The new numbers are:

Anti squat: 164.94
Roll axis: 1.97
Roll center: 19.96

What are you using for a COG?
What is your tire diameter?

Here is the current front I am planning.
The Y value on the upper link should actually be -11

if I move the lower link frame ends to the actual bottom of the frame
48/15/17

And the AS goes to 50% the RAA to 0 and the RC to 22

With the link on the bottom of the frame instead of off to the side

I just re-entered the data using the lower as upper and upper as lower. The graph now represents my set-up better. I also moved the COG. 26 seemed low. The new numbers are:

Anti squat: 164.94
Roll axis: 1.97
Roll center: 19.96

Here is what I got using your numbers.... i think:D

Here is what I got using your numbers.... i think:D

Thats exactly what I got. But I am not sure if the Roll axis is tied to always the lower, or always the double links. If it is always the double links, it's really not that bad. If it is always tied to the lower link, then it explains why rover people have thought 3 links arn't that good for on road driving.

I have tons of questions for you on your link numbers. I will PM you when I have a moment.

I have tons of questions for you on your link numbers. I will PM you when I have a moment.

i don't mind public discussion, specially if I really f-ed something. Figure it will help others.

I almost started a new thread, but figured it made sense to keep it all in one spot.

And an important piece of information to keep in mind is the fact that my engine is much further back then is typical. Not quite a mid engine, but figure the rear bank of cylinders will be on the drivers side of the bulkhead. So even with the big v8 I will still have a Series looking front end, I can lower the engine a little bit for better COG and the weight will be more balanced f-2-r

Pete

Thats exactly what I got. But I am not sure if the Roll axis is tied to always the lower, or always the double links. If it is always the double links, it's really not that bad. If it is always tied to the lower link, then it explains why rover people have thought 3 links arn't that good for on road driving.

I thought it was based on the doubles. Because the angle of the two to each other and their angle to the ground seem to have more of an effect.

i don't mind public discussion, specially if I really f-ed something. Figure it will help others.

You probably want higher AS (anti-dive in this case) to prevent it diving like a 70s Ford under braking.

The real trick in a lot of this is choosing a real CG location and then moving it around to simulate differing loading that you will actually see. Remember, the CG is for the sprung mass only.

You probably want higher AS (anti-dive in this case) to prevent it diving like a 70s Ford under braking.

The real trick in a lot of this is choosing a real CG location and then moving it around to simulate differing loading that you will actually see. Remember, the CG is for the sprung mass only.

Well if I drop the upper link frame Z down to 20" I get a AS of 83.9 and the Roll Axis stays at 0.

Drop the Z down to 18" and AS = 101, RAA=0, RCH = 22
If we are just building by the numbers thats about perfect for the front right?
But I thought I wanted to keep the upper and lower frame ends vertically separated?

Looks like I can get the same numbers if I leave the upper frame Z at 24, but go from a 48" link to a 19" link. Not sure thats such a good idea. As the suspension drops I think the pinion ends up pointing straight down at the ground :D

35in tires
36 COG
Panhard is -4 at axle -8 at frame

... It's the braking I'm trying to get improved. It pulls left pretty hard.
...suggestions? Longer uppers, relocate center link pivot closer to axle, longer center, ???
With front suspension, during hard braking, the lower link/links is/are in compression.

If the lower links are not symmetrical, i.e. single lower on centerline of front axle, or 2 lowers equal spaced from centerline, the front axle can turn one way.

This is why it is better to have 2 lowers and 1 upper, rather than 1 lower and 2 uppers like SG.

Your lower link is close to symmetrical but not quite. I can't think why the frame end would need to be offset like it is, but I think it may be why yours pulls left when braking.

Well if I drop the upper link frame Z down to 20" I get a AS of 83.9 and the Roll Axis stays at 0.

Drop the Z down to 18" and AS = 101, RAA=0, RCH = 22
If we are just building by the numbers thats about perfect for the front right?
But I thought I wanted to keep the upper and lower frame ends vertically separated?

Looks like I can get the same numbers if I leave the upper frame Z at 24, but go from a 48" link to a 19" link. Not sure thats such a good idea. As the suspension drops I think the pinion ends up pointing straight down at the ground :D
During braking, your upper link is in tension. It is pulling the frame up, which is where the anti-dive comes from. The steeper it is the more force it lifts as you see in your spreadsheet results.

But remember that your upper link is offset a lot, so higher anti-dive will come with more body roll at the same time (while braking). So it may be better to not try for very high anti-dive.

Edit: unless it is for improving suspension behaviour (eg roll axis, anti-...), or fitting in links, there is no engineering reason to have vertical separation between upper and lower links at the frame end (unlike at axle end where it affects the magnitude of the link forces).

... But I am not sure if the Roll axis is tied to always the lower, or always the double links. If it is always the double links, it's really not that bad. If it is always tied to the lower link, then it explains why rover people have thought 3 links arn't that good for on road driving.

...
IMHO the roll axis will be determined by the double links. The single link cannot fix the lateral location of the frame.

The roll axis passes through the center of the panhard rod and the theoretical point where the double links converge. Parallel links converge at infinity so roll axis is parallel to them. aloharover's lower links are not parallel, but converge a long way back so his RA is close to parallel with the lowers.

Well if I drop the upper link frame Z down to 20" I get a AS of 83.9 and the Roll Axis stays at 0.

Try raising the frame end of the lowers a bit instead of dropping the upper so much. I know it adds some roll axis, but you need to think of clearance as well. Seems low and exposed there. How high is the bottom of the frame?

As stated, frame end separation is not required.

During braking, your upper link is in tension. It is pulling the frame up, which is where the anti-dive comes from. The steeper it is the more force it lifts as you see in your spreadsheet results.

But remember that your upper link is offset a lot, so higher anti-dive will come with more body roll at the same time (while braking). So it may be better to not try for very high anti-dive.

Edit: unless it is for improving suspension behaviour (eg roll axis, anti-...), or fitting in links, there is no engineering reason to have vertical separation between upper and lower links at the frame end (unlike at axle end where it affects the magnitude of the link forces).

That makes perfect sense. I mean I can see in the picture how if I drop the upper frame mount, it will have a lifting effect on braking.

Now does this mean that under braking the front axle will also see more trasnfered weight onto it and thus, better braking?

I do also see how sharp braking will cause the body to roll to the right. No room to center the frame end, but I do have room to build a Y. And could center the front. Well I guess that lets me loose the panhard. Seesh back to copying the rear.

With front suspension, during hard braking, the lower link/links is/are in compression.

If the lower links are not symmetrical, i.e. single lower on centerline of front axle, or 2 lowers equal spaced from centerline, the front axle can turn one way.

This is why it is better to have 2 lowers and 1 upper, rather than 1 lower and 2 uppers like SG.

Your lower link is close to symmetrical but not quite. I can't think why the frame end would need to be offset like it is, but I think it may be why yours pulls left when braking.



Nevermind...I need to read before I reply!

Going to center the CL pronto!!

Edit: unless it is for improving suspension behaviour (eg roll axis, anti-...), or fitting in links, there is no engineering reason to have vertical separation between upper and lower links at the frame end (unlike at axle end where it affects the magnitude of the link forces).

Whoa, not true!

Vertical separation at the frame end is what keeps the front end from unloading going up hill. This is one of the most important things about a link suspension. And why my truck climbs like a mountain goat. I wanted to get to 7in of separation at the frame, but couldn't get there. The calculator doesn't bring this into play, but trust me, it's important.

Nevermind...I need to read before I reply!

Going to center the CL pronto!!

Hold up. This can only happen if you have play in your links. Without play, any amount of offset will mean nothing. Are you running poly bushings instead of hiems? If so, then yes, this could be causing your issue as the links will allow the axle to move. But if they are all solid links, something else is causing your issue.

That makes perfect sense. I mean I can see in the picture how if I drop the upper frame mount, it will have a lifting effect on braking.

Now does this mean that under braking the front axle will also see more trasnfered weight onto it and thus, better braking?

I do also see how sharp braking will cause the body to roll to the right. No room to center the frame end, but I do have room to build a Y. And could center the front. Well I guess that lets me loose the panhard. Seesh back to copying the rear.

Not to repeat myself, but hard braking will not cause the front to go any way regardless of upper link placement unless there is some movement in your links. IE, bushings or a worn out JJ. Even then, I don't really see it being that much of an issue.

Don't dump the panhard unless you are running full hydro.

edit: I have a bunch of questions for you, but need to get my skid done first!

Hold up. This can only happen if you have play in your links. Without play, any amount of offset will mean nothing. Are you running poly bushings instead of hiems? If so, then yes, this could be causing your issue as the links will allow the axle to move. But if they are all solid links, something else is causing your issue.

Frame end is bushing. Axle end is joint.

Not to repeat myself, but hard braking will not cause the front to go any way regardless of upper link placement unless there is some movement in your links. IE, bushings or a worn out JJ. Even then, I don't really see it being that much of an issue.

Yes it can. Whether it does in a noticable way depends on at least a dozen other factors. But it certainly can.

Take the extreme case of the top link above one of the side links. Apply torque to the axle (braking or acceleration) and it is resolved back to the chassis through one side only. The result is one side gets all the squat/antisquat reaction, the other is only providing thrust.

You can design an off-centre middle link to provide equal squat/antisquat to each side, but it's going to get complicated fast.

Yes it can. Whether it does in a noticable way depends on at least a dozen other factors. But it certainly can.

Take the extreme case of the top link above one of the side links. Apply torque to the axle (braking or acceleration) and it is resolved back to the chassis through one side only. The result is one side gets all the squat/antisquat reaction, the other is only providing thrust.

You can design an off-centre middle link to provide equal squat/antisquat to each side, but it's going to get complicated fast.

Yes, you are right. I read Aloha's post too fast and thought he was still talking about what Bush was with the axle "turning" during braking.

Frame end is bushing. Axle end is joint.

I don't think thats it, but you can replace them with hiems and see if your braking issue goes away. My guess is something is bent. But it's a total guess.

I don't think thats it, but you can replace them with hiems and see if your braking issue goes away. My guess is something is bent. But it's a total guess.

I'm going to move the axle end tabs over to center tomorrow after work. It's free. Can't hurt to try...

I'm going to move the axle end tabs over to center tomorrow after work. It's free. Can't hurt to try...

word.

Wow, shit's getting deep around here... Anyone wanna buy life insurance before shit hits the fan?:flipoff2: Just kidding, this has been great guys, keep up the good discussion and the good fab work.

Whoa, not true!

Vertical separation at the frame end is what keeps the front end from unloading going up hill. This is one of the most important things about a link suspension. And why my truck climbs like a mountain goat. I wanted to get to 7in of separation at the frame, but couldn't get there. The calculator doesn't bring this into play, but trust me, it's important.

The unloading only is controlled by the AS (anti-dive) numbers on the front end. High antidive will cause the front to dive under power, which is what I assume you mean by "unloading". The actual separation means little, it is the AS geometry that matters.

Bush65 is a very knowledgeable person in this area.....

I "think" what you really mean is that low anti-dive numbers give better climbing performance, similar to how some people contend high antisquat does the same for the rear.

The unloading only is controlled by the AS (anti-dive) numbers on the front end. High antidive will cause the front to dive under power, which is what I assume you mean by "unloading". The actual separation means little, it is the AS geometry that matters.

Bush65 is a very knowledgeable person in this area.....

I "think" what you really mean is that low anti-dive numbers give better climbing performance, similar to how some people contend high antisquat does the same for the rear.

No. Thats not what I mean. AS or antidive is a separate issue. I meant exactly what I said. Vertical separation at the frame is extremely important for climbing. I can't describe why without serious effort. It will not necessarily show up in the calculators but it is extremely important. You can take my word for it or not, but I am sure about it.

Yes, you are right. I read Aloha's post too fast and thought he was still talking about what Bush was with the axle "turning" during braking.
The axle turning is an issue if you have 2 uppers and an eccentric lower.

I never said Aloha will have a problem with axle turning. He is proposing 2 lowers and 1 upper - so he shouldn't have that problem.

I only cautioned him about trying to get a large ant-dive number because of the roll issue with the upper link offset so far.

The flip side of the eccentric upper link is it counters torque roll which can help a lot when you are close to tipping to the right. The amount of eccentricity to negate torque roll is related to the diff ratio. But the engine sump may prevent getting it exact.

In finding a good compromise, I'm sure he could live with more dive and a small amount of roll during hard braking, as long as neither are too bad.

...
Edit: unless it is for improving suspension behaviour (eg roll axis, anti-...), or fitting in links, there is no engineering reason to have vertical separation between upper and lower links at the frame end (unlike at axle end where it affects the magnitude of the link forces).

Whoa, not true!

Vertical separation at the frame end is what keeps the front end from unloading going up hill. This is one of the most important things about a link suspension. And why my truck climbs like a mountain goat. I wanted to get to 7in of separation at the frame, but couldn't get there. The calculator doesn't bring this into play, but trust me, it's important.
I sensed that Aloha believed that for some unknown reason, he could not reduce the vertical separation at the frame end.

I'm did not advocate no separation at the frame, and did say use separation if it improves suspension behaviour.

My position is, if suspension geometry/behaviour is better with the less separation there are no engineering reasons for making the separation larger and degrading suspension behaviour.

I believe, like red90rover said, your climbing performance is to do with the anti-squat, not simply because the vertical frame separation is x number of inches.

When you look at the data output from the 3-link spreadsheet, you are only seeing one situation (when the vehicle is on flat level ground and the suspension is not moving).

When the suspension loads/unloads, the position of the IC (instantaneous centre) changes and this will change the numbers for anti-squat etc. Some link geometry might look good when static, but be poor when the suspension loads/unloads.

Some people have deliberately located the frame end of links at a good location for the IC so that the IC does not move, or moves very little as the suspension moves.

If you spend time looking at the suspension geometry and results, with the wheel in different positions to represent what happens as it loads/unloads, you will most likely find that vertical separation is indeed needed to get a desirable change in IC position (and change in anti-squat) so the suspension will work better.

A good example for what to avoid is rear suspension where anti-squat increases as the suspension unloads. This causes the vehicle to buck when climbing.

When the vehicle is climbing the location of the centre of gravity causes the weight distribution to reduce at the front wheels and increase at rear wheels. This is where you can benefit from geometry that changes the anti-squat so it works for you and not make it worse.

It would be just as easy to have poor suspension geometry with large vertical frame separation as it would be to have better suspension with less separation. Having x number of inches separation is a bad rule and is no substitute for good geometry.

However, going off other suspension geometry that is known to work well is a good starting point, and possibly could be improved upon. But as we know, other things tend to get in our way and at times compromises have to be made.

All true. No disagreement. But saying that vertical separation at the frame doesn't matter is not true. Which is how I read your post. Maybe I misunderstood your post. I never advocated a set number. I told what I was shooting for. VS at the frame end is more important than most people think.

I thought that I had read in one of the hundreds of suspension threads on this site that you need vertical seperation at the frame.
I know you need a "lot" at the axle for strength, but the frame end still needed a little seperation.

The bottom of my frame is 17.5 from the ground when the axle center is 17 up and 8" between top of axle and under side of frame.
I am set up for 14" coil overs with 6" compression and 8" drop.
Was thinking of using limit straps in the center of the axles to prevent full unloading front and rear. I want the ability to cross up, but think full droop would be bad.

I am trying to build something that will perform well off road while remaining safe as a daily driver. I will run chinaman, iron chest, iron mike and such. But dont think I will ever do Holy Cross, Indi, etc.
I am building the truck longer so that it behaves better on and off road, but also so I can add a second row of seats for the kids, or so that I have more storage room for longer trips.

Yes I could leave the front and rear as a stock RRA suspension, or even the parabolics, but that wouldn't be any fun :D

Honestly Aloha,

you know enough at this point where you simply won't build a bad setup. Don't stress. We have to talk about link lenth overall and uppers v lower lenth but your numbers are great. Better than mine and I'm happy.

I have the space to run 4' links front and rear.
I know that if upper and lower are equal in length and parrallel then the caster/camber wont change as the suspension moves.
If they are not parrellel, then they need to be different length to make this happen.
So I want to do the math to figure out the correct length and location for the upper link.

if the numbers on the calc are right, then just shorten the top, but keep it in the same plane

No. Thats not what I mean. AS or antidive is a separate issue. I meant exactly what I said. Vertical separation at the frame is extremely important for climbing. I can't describe why without serious effort. It will not necessarily show up in the calculators but it is extremely important. You can take my word for it or not, but I am sure about it.

I'm saying that it is what you mean, it is just that you do not realise it. Having the larger separation give low anti-dive that does not change much with suspension travel, which results in the behaviour you want...

I'm saying that it is what you mean, it is just that you do not realise it. Having the larger separation give low anti-dive that does not change much with suspension travel, which results in the behaviour you want...

No, it's not. I don't have low anti-dive. I see what your trying to get at though. It's just not what I am talking about.

I have the space to run 4' links front and rear.
I know that if upper and lower are equal in length and parrallel then the caster/camber wont change as the suspension moves.
If they are not parrellel, then they need to be different length to make this happen.
So I want to do the math to figure out the correct length and location for the upper link.

if the numbers on the calc are right, then just shorten the top, but keep it in the same plane

Links that are parrallel cause the IC to migrate a lot more (wr.t. the chassis) than links which angle in to converge closer to the frame mounts.

It's a subject that gets extremely complicated, very quickly. At some point everyone will say "screw it, I'm building it anyway".:smokin:

OK...I went to my buddy's shop to move the CL tab last week. He says there is no reason to mess with it. He doesn't see how it coud be causing my problem. That said, I just got back from TN and the truck acted like a blind retard. I'm looking for suggestions. What would help make the truck behave "better?" Longer CL with a slower angle? Relocate the center mount higher? It's pretty low now because of where it mounts on the SG kit. I've been messing with the numbers on the calculator, but I'm not sure where I need them.

Thanks for all of the help so far. I think I'm getting a better grasp on this.


Chad

I don't think thats it, but you can replace them with hiems and see if your braking issue goes away. My guess is something is bent. But it's a total guess.

OK...I went to my buddy's shop to move the CL tab last week. He says there is no reason to mess with it. He doesn't see how it coud be causing my problem. That said, I just got back from TN and the truck acted like a blind retard. I'm looking for suggestions. What would help make the truck behave "better?" Longer CL with a slower angle? Relocate the center mount higher? It's pretty low now because of where it mounts on the SG kit. I've been messing with the numbers on the calculator, but I'm not sure where I need them.

Thanks for all of the help so far. I think I'm getting a better grasp on this.


Chad

I never thought it was the links. My next stop would be an alignment shop to see if something is out of wack.

With front suspension, during hard braking, the lower link/links is/are in compression.

If the lower links are not symmetrical, i.e. single lower on centerline of front axle, or 2 lowers equal spaced from centerline, the front axle can turn one way.

This is why it is better to have 2 lowers and 1 upper, rather than 1 lower and 2 uppers like SG.

Your lower link is close to symmetrical but not quite. I can't think why the frame end would need to be offset like it is, but I think it may be why yours pulls left when braking.

OK...I went to my buddy's shop to move the CL tab last week. He says there is no reason to mess with it. He doesn't see how it coud be causing my problem. That said, I just got back from TN and the truck acted like a blind retard. I'm looking for suggestions. What would help make the truck behave "better?" Longer CL with a slower angle? Relocate the center mount higher? It's pretty low now because of where it mounts on the SG kit. I've been messing with the numbers on the calculator, but I'm not sure where I need them.

Thanks for all of the help so far. I think I'm getting a better grasp on this.


Chad
In my earlier post (quoted above) I said I thought the off center frame mount of the lower link may be why you have a problem pulling to left when braking.

I was under the impression that you had been able to rule out the other possible problems.

For you benefit, I put your numbers into the 3 link calculator to look at what the link forces are, to be able to point out why the problem can arise.

Unfortunately the 3 link calculator has not been properly sorted (still beta AFAIK).

It assumes symmetrical links when calculating the forces in the red links (labeled lower in calculator, but actually uppers for SG type 3 links).

The calculated forces in the panhard look way too high, but I haven't taken the trouble to determine what is going on there.

For simplicity in calculating the link forces, the calculator makes some assumptions about weight transfer to the tires and friction factor between tire and road. I have no issue with the approach or the assumptions, but remember that the actual forces should be less than these, but in much the same proportions between upper and lower links.

Before looking at the forces, remember that the calculator is based on rear suspension. Below I will be discussing braking and front SG type 3 link.

During braking (assuming forward motion), the friction force between the tires and the road is pushing rearward on the tires/axle. To the right in the diagrams on the 3 link calculator.

In turn the axle pushes rearward against the frame through the lower link (blue link in the calculator). The lower link is in compression.

Now the upper links (red links in the calculator) must be in tension to prevent the axle assembly from rotating. This means that the upper links are pulling the axle rearward.

The calculator presents the forces in the links in the Material sheet. I have not loaded pics of this as there was a 5 pic per post limit. The forces are:
Blue link (lower link in SG 3 link) 22,597 lbs compression
Red links (each upper link in SG 3 link) 4,182 lbs tension (each link)

The calculator presents the forces in the x,y,z coordinate directions in the Calculations sheet. See 3rd (blue lower link), 4th (red upper links), and 5th (yellow panhard link) pics below.

Looking at these results, the blue link is pushing against the frame with a force of:
21,725 lbs in X direction (to decelerate vehicle)
1,509 lbs in y direction (pushing frame to left and axle to right)
6,034 lbs in z direction (pushing up on frame - this is producing the anti-dive)

If the frame end of the lower link was on center, the force in y direction would be zero.

Because it is not on centre it is trying to push the frame to the left (1,509 lbs) and the axle end of the lower link is pushing the axle to the right (1,509 lbs).

Now the panhard resists the axle being pushed to the right, and so is in tension and tries to pull the frame end of the frame to the right.

Now look at the forces that are trying to steer the front axle:

The horizontal (x direction) separation between the axle ends of the lower link and panhard is 14" (panhard is 4" in front, lower link is 10" behind).

At the lower link mount there is 1,509 lbs pushing to the right.

At the panhard mount there will be some force ??? lbs (ignore 28,606,761 lbs in 3 link calculator) pulling to left.

The tension in the left upper link will increase by ??? lbs, the tension in the right upper link will reduce by ??? lbs.

The unknown forces (??? lbs) result from the complex nature of the system.

It is clear that the offset of the lower link is trying to steer the axle to the left.

Buck will probably say this won't happen if there is no flex in the mounts/links. But there will always be some flex.

The SG type is more prone to this problem because it has 2 upper and 1 lower link. The force in the links out near the wheels (uppers) are pulling the axle in the same direction as the braking force.

Just to repeat what was implied near the beginning of this post, the braking force should be less than assumed by the calculator (limited by tire friction and load). The link forces will be proportionally lower, but the effects are still there.

Buck will probably say this won't happen if there is no flex in the mounts/links. But there will always be some flex.

He has a poly bushing in the center link, so it's entirely possible. Great post.

Still don't think this is causing it. Wanna put a $10 spot on it!? Lord knows I've been wrong before. :D

He has a poly bushing in the center link, so it's entirely possible. Great post.

Still don't think this is causing it. Wanna put a $10 spot on it!? Lord knows I've been wrong before. :D
I have had a normal 3 link (2 lowers and offset upper) in a truck and considering it again for my current project (but need to get more stuff installed to see what clearance I have for the upper link).

IMHO there are no issues with a properly set up system using 2 lower links, a single upper link plus panhard that can't be overcome with swaybars (and there are simple ways to manage swaybars off road).

But using a single lower link, 2 upper links and panhard is a completely different animal as I see it. Although I am aware the SG kit has been proven, I can't come around from my belief that it is the wrong way to build a 3 link front suspension that will be used on the road.

I am not concerned about the failure of the cross member in the early trial that some people always bring up - that is just showed that the stock rover cross member is not adequate to withstand the lower link loads.
I haven't had anything to do with the SG 3 links. I'm only going from photos, reports and knowledge of mechanical matters.

The potential for poor stability under heavy braking is what I find unacceptable (unlike systems with 2 lower links). They are inherently unforgiving if everything is not spot on. There is no getting around that IMHO.

The 4 link and 3 link calculators are good tools for finding how the anti-squat/dive, roll axis etc. Link loads were included as a guide for selecting reasonable material sizes for links and joints when used with suitable safety factors. But it is not software for accurate calculation of links loads with regard to vehicle dynamics - this was never intended.

The dynamics are very complex and best left to smarter people than me.

The fact is, we have to use good judgment, study and learn from others, and take small steps when we build stuff that can't be evaluated properly.

Can anyone tell me if any other SG 3 links have the frame end mount for the lower link off center like this one?

I had been expecting/hoping that soon after my 1st post on this someone would post up that they were all made this way and no one has .......

Then I would search for some reasoning in the dynamic behavior where it might be counteracting some imbalance.

But at the moment, without spending much more time on something that I don't expect any personal benefit from, I can't see any good reason, and only see problems from doing this.

Edit: That is my take Buck. I'm not concerned with what I have posted and am happy to stand by them and more than happy to be corrected and learn where I am wrong or mistaken. In regard to the the offset lower link, my 1st impression was it was not far off to be greatly concerned about, but then thought it may be the problem and posted to point out something which should be looked at.

If you want to have $10 on this, the only thing I ask is that you be more specific as to what exactly has to be done to fix it.:D

Mainly I just want to see the problem fixed, but not just a band aid to mask the underlying problems.

Incorrect info...

Buck...I'll take the bet.

Chad

The frame end is centered, and has a teraflex joint. The axle end is off centered, and has a large bushing. This is NOT standard with SG 3-links. Mine has been modified to address clearance issues present because of my swivels being corrected 3deg. So...when the shop put a larger box around the drag link, they did a poor job measuring. (don't worry, I don't go to them anymore)

My welding skills are not up to this task, therefore I'm waiting on a friend to help. Otherwise I would have already moved the fucker just to rule it out as a cause. Should get it moved in the next day or two.

Buck...I'll take the bet.

Chad

Saweet! Wait, how can you be trusted? You'll just say all is okay after moving it. :laughing:

I have had a normal 3 link (2 lowers and offset upper) in a truck and considering it again for my current project (but need to get more stuff installed to see what clearance I have for the upper link).

IMHO there are no issues with a properly set up system using 2 lower links, a single upper link plus panhard that can't be overcome with swaybars (and there are simple ways to manage swaybars off road).

But using a single lower link, 2 upper links and panhard is a completely different animal as I see it. Although I am aware the SG kit has been proven, I can't come around from my belief that it is the wrong way to build a 3 link front suspension that will be used on the road.

I am not concerned about the failure of the cross member in the early trial that some people always bring up - that is just showed that the stock rover cross member is not adequate to withstand the lower link loads.
I haven't had anything to do with the SG 3 links. I'm only going from photos, reports and knowledge of mechanical matters.

The potential for poor stability under heavy braking is what I find unacceptable (unlike systems with 2 lower links). They are inherently unforgiving if everything is not spot on. There is no getting around that IMHO.

The 4 link and 3 link calculators are good tools for finding how the anti-squat/dive, roll axis etc. Link loads were included as a guide for selecting reasonable material sizes for links and joints when used with suitable safety factors. But it is not software for accurate calculation of links loads with regard to vehicle dynamics - this was never intended.

The dynamics are very complex and best left to smarter people than me.

The fact is, we have to use good judgment, study and learn from others, and take small steps when we build stuff that can't be evaluated properly.

Can anyone tell me if any other SG 3 links have the frame end mount for the lower link off center like this one?

I had been expecting/hoping that soon after my 1st post on this someone would post up that they were all made this way and no one has .......

Then I would search for some reasoning in the dynamic behavior where it might be counteracting some imbalance.

But at the moment, without spending much more time on something that I don't expect any personal benefit from, I can't see any good reason, and only see problems from doing this.

Edit: That is my take Buck. I'm not concerned with what I have posted and am happy to stand by them and more than happy to be corrected and learn where I am wrong or mistaken. In regard to the the offset lower link, my 1st impression was it was not far off to be greatly concerned about, but then thought it may be the problem and posted to point out something which should be looked at.

If you want to have $10 on this, the only thing I ask is that you be more specific as to what exactly has to be done to fix it.:D

Mainly I just want to see the problem fixed, but not just a band aid to mask the underlying problems.

I hope you don't think I am being unreasonable with you. I agree with everything you have said here minus only the VS at the frame comment. I don't have a SG 3 link, and I was interested in getting the numbers on it because it has always just looked wrong. Not really any reason, but I thought the AS would be through the roof.

Here is the only reason why I don't think it is the lower link being an inch off. I've installed one of these things. The one I installed had two poly busings on the center link both welded. It had a one tube bigger than the other fitted together like a telescope. There was threading on both tubes, I mean like cheese ball threading, in mild steel tubing. The thing was hokey as shit. So why does this matter? Well, I just can't believe that enough force could ever be transfered to that center link that is 1in off to cause diving to the left, and not break that little link in two.

That threaded link could be way stronger than I think. But I am willing to throw 10 bucks on it that it is not causing his issue.

You'll know if I'm BSing because I'll still be on here whining like a bitch if it doesn't work!

(e-shake on it)

Chad

Update...I'm at my buddy's shop now taking some measurements. The frame end mount is off center 1.5in to passenger. The axle end mount is off 1.5in. passenger. Is this acceptable?

Buck, this may change the peramiters of our wager!
:D

Chad

edit: just talked to SG, the 3-links are this way

I have had a normal 3 link (2 lowers and offset upper) in a truck and considering it again for my current project (but need to get more stuff installed to see what clearance I have for the upper link).

IMHO there are no issues with a properly set up system using 2 lower links, a single upper link plus panhard that can't be overcome with swaybars (and there are simple ways to manage swaybars off road).

But using a single lower link, 2 upper links and panhard is a completely different animal as I see it. Although I am aware the SG kit has been proven, I can't come around from my belief that it is the wrong way to build a 3 link front suspension that will be used on the road.

I am not concerned about the failure of the cross member in the early trial that some people always bring up - that is just showed that the stock rover cross member is not adequate to withstand the lower link loads.
I haven't had anything to do with the SG 3 links. I'm only going from photos, reports and knowledge of mechanical matters.

The potential for poor stability under heavy braking is what I find unacceptable (unlike systems with 2 lower links). They are inherently unforgiving if everything is not spot on. There is no getting around that IMHO.

The 4 link and 3 link calculators are good tools for finding how the anti-squat/dive, roll axis etc. Link loads were included as a guide for selecting reasonable material sizes for links and joints when used with suitable safety factors. But it is not software for accurate calculation of links loads with regard to vehicle dynamics - this was never intended.

The dynamics are very complex and best left to smarter people than me.

The fact is, we have to use good judgment, study and learn from others, and take small steps when we build stuff that can't be evaluated properly.

Can anyone tell me if any other SG 3 links have the frame end mount for the lower link off center like this one?

I had been expecting/hoping that soon after my 1st post on this someone would post up that they were all made this way and no one has .......

Then I would search for some reasoning in the dynamic behavior where it might be counteracting some imbalance.

But at the moment, without spending much more time on something that I don't expect any personal benefit from, I can't see any good reason, and only see problems from doing this.

Edit: That is my take Buck. I'm not concerned with what I have posted and am happy to stand by them and more than happy to be corrected and learn where I am wrong or mistaken. In regard to the the offset lower link, my 1st impression was it was not far off to be greatly concerned about, but then thought it may be the problem and posted to point out something which should be looked at.

If you want to have $10 on this, the only thing I ask is that you be more specific as to what exactly has to be done to fix it.:D


Mainly I just want to see the problem fixed, but not just a band aid to mask the underlying problems.

With respect to a non centered center link, I believe Ed Maggofin's old D90 had an early SG 3 link that Rockware modified and it seems that the center link was mounted on top of the differential. I also recall Rich Hills, who is more than qualified to make engineering statements, indicated an offset link was in fact a favorable setup. It may be in a post here or on d-90.com, can't remember.

Buck, this may change the peramiters of our wager!
:D

Chad

I'll say. It means you owe me $10! I accept paypal.

Being right this much is exausting. :flipoff2:

I'll say. It means you owe me $10! I accept paypal.

Being right this much is exausting. :flipoff2:

Does Paypal have a "I lost a bet" category?
:grinpimp:

I'm going by the tire shop in the AM. I know the toe is good. I'm going to have them check wheelbase, etc... I picked up an unlimited alignment deal a few years back, so what the hell...

Double or nothing?

Whoa, not true!

Vertical separation at the frame end is what keeps the front end from unloading going up hill. This is one of the most important things about a link suspension. And why my truck climbs like a mountain goat. I wanted to get to 7in of separation at the frame, but couldn't get there. The calculator doesn't bring this into play, but trust me, it's important.

Is the total lack of vertical separation at the frame in a stock radius arm setup the reason for the power hop I get at the front axle when climbing?

Does Paypal have a "I lost a bet" category?
:grinpimp:

I'm going by the tire shop in the AM. I know the toe is good. I'm going to have them check wheelbase, etc... I picked up an unlimited alignment deal a few years back, so what the hell...

Double or nothing?

Sure, what are we betting on? :D

Is the total lack of vertical separation at the frame in a stock radius arm setup the reason for the power hop I get at the front axle when climbing?

It is A cause, whether or not it is THE cause I can not say. There are a ton of other factors.

[QUOTE=Buckon37s;10473031]Sure, what are we betting on? :D

No clue...just want to win something!

Is the total lack of vertical separation at the frame in a stock radius arm setup the reason for the power hop I get at the front axle when climbing?

Are you lifted a lot and on big tires? If so, your anti-dive numbers are probably really high on the front, as stock should already be above 100%. You will get a lot of tire lift under power. With really high numbers, things hop due to the instability. With a radius arm design, the only reasonable solution is longer arms. With a multilink, there is a lot more flexibility.

It is all about the anti-dive numbers and not the vertical separation, despite how much Buck wants to believe there is magic happening somewhere......

Are you lifted a lot and on big tires? If so, your anti-dive numbers are probably really high on the front, as stock should already be above 100%. You will get a lot of tire lift under power. With really high numbers, things hop due to the instability. With a radius arm design, the only reasonable solution is longer arms. With a multilink, there is a lot more flexibility.

It is all about the anti-dive numbers and not the vertical separation, despite how much Buck wants to believe there is magic happening somewhere......

You know, you can disagree with me all you want but I'm right. Don't confuse me with someone who needs others to agree with me for reinforcement. Your theory about antsquat changing less during travel with more vertical separation is nice, whatever. But I'm not talking about the front moving, so it doesn't apply.

So take it or leave it.

You know, you can disagree with me all you want but I'm right. Don't confuse me with someone who needs others to agree with me for reinforcement. Your theory about antsquat changing less during travel with more vertical separation is nice, whatever. But I'm not talking about the front moving, so it doesn't apply.

So take it or leave it.

Normally having more vertical separation gives a lower anti-dive value as the instant center is moved back farther. This lower antidive is what is giving the effect you want. As power is applied, the front tires push down. Also with the instant center a long way back, it is more stable as the geomtery changes with movement are very small and the effect of the gradient is much less.

With a high anti-dive (well above 100%), the tires will lift, causing a loss in traction, followed by the tires falling, grabbing traction, and so on.... Giving the hop effect. The same would happen in the rear with very low anti-squat.

Normally having more vertical separation gives a lower anti-dive value as the instant center is moved back farther. This lower antidive is what is giving the effect you want. As power is applied, the front tires push down. Also with the instant center a long way back, it is more stable as the geomtery changes with movement are very small and the effect of the gradient is much less.

With a high anti-dive (well above 100%), the tires will lift, causing a loss in traction, followed by the tires falling, grabbing traction, and so on.... Giving the hop effect. The same would happen in the rear with very low anti-squat.

Thats all fine and dandy. But that's not all of it. And AS is only a factor, not the whole thing. I ran lower AS (barely) on my mounted over the axle radius arms than I did one my 3 link. The 3 link climbs much better. And does not unload like the radius arms did. Once again, I don't run low AS.

There is a big difference between unloading on near vertical climbs and bouncing, even though we have discussed both. Usually bouncing has a lot to do with being over sprung.

I ran lower AS (barely) on my mounted over the axle radius arms than I did one my 3 link. The 3 link climbs much better. And does not unload like the radius arms did. Once again, I don't run low AS.

I'm calling BS. Let's see the numbers. A radius arm setup has the IS at the pivot. Mounting over or under has zero affect. With a tall truck that gives a very high anti-dive number. Unless your 3 link is pointing to the sky, the anti-dive must be low.....

I'm calling BS. Let's see the numbers. A radius arm setup has the IS at the pivot. Mounting over or under has zero affect. With a tall truck that gives a very high anti-dive number. Unless your 3 link is pointing to the sky, the anti-dive must be low.....

Call bs all you want. My radius arms were 8 in longer than stock and mounted just below the frame. My 3 link is non trangulated with a different frame mount. I just changed it with the new frame so now it is at 80 something but it used to be over 100. Once again, I don't run low AS. My truck is not that tall btw. Are we done?

Lets see the numbers on the radius arm setup and the 3 link.... Stock is well over 100. Your truck is certainly taller than stock (your radius arm mount was higher off of the ground). We are not done until you bring facts to the table :flipoff2:.

Lets see the numbers on the radius arm setup and the 3 link.... Stock is well over 100. Your truck is certainly taller than stock (your radius arm mount was higher off of the ground). We are not done until you bring facts to the table :flipoff2:.

You first!

I don't have the radius arm numbers saved. I had multiple radius arm mounts. I can send you the new ones when I get home. My truck has somewhere between no lift and 2in. It's not that tall.

Your still not getting what I am saying. A truck can have high AS with VS and vice versa. But, when you go vertical, the VS at the frame makes a difference in how the front unloads. Regardless of what AS it starts with. If it was only AS then everybody would run 0. AS plays a roll, but vs is important. It makes perfect sense as you picture a truck going vertical.

2" spring lift plus 4"? tire lift.... I'll try and measure a 90 later and post. All we need is a side view of your truck when it had a radius arm.

Line from tire contact thorough the radius arm pivot point and you can see the geometry right away.

2"??
http://www.pirate4x4.com/forum/attachment.php?attachmentid=220830&stc=1&d=1135452854

8"??
http://www.pirate4x4.com/forum/attachment.php?attachmentid=220832&stc=1&d=1135452910

Can't seem to find a good side view.

2" spring lift plus 4"? tire lift.... I'll try and measure a 90 later and post. All we need is a side view of your truck when it had a radius arm.

Line from tire contact thorough the radius arm pivot point and you can see the geometry right away.

Yes, 0-2in lift. I don't know exacty anymore. Tires don't matter to link angles. Yes 8in longer. Those pics are 4 years old and two mounts ago. I'll try to find a pic from the side.

Now, do you get it with my last post or are you still saying a
AS is all that matters?

Yes, tire height matter. Time to look up how AS is calculated... So the frame is only 2" higher with respect to the axle centerline compared to a stock 90?? The picture above looks higher to me.

Here is ONLY a sample to show how the radius arms give a high AS. As a truck is lifted via tires or springs, the AS line goes up faster than the CG line making the AS percentage increase with lift.

Yes, tire height matter. Time to look up how AS is calculated... So the frame is only 2" higher with respect to the axle centerline compared to a stock 90?? The picture above looks higher to me.

How does tire size affect link angles/antisquat. I really don't see that. Yes, again, I have between 0-2in of lift compared to a stock d90. According to front fender line. In the pic you posted I had a 3.75in lift I think.

So again, are you still saying it is all antisquat? How do you explain my rig climbing so well with high AS? Still think VS at the frame makes no difference? Have you experienced the difference in the real world?

I am not sure you know what we are arguing about anymore.

How does tire size affect link angles/antisquat.
Are you joking here??? Please go and try and understand the concept so we can have an intelligent discussion.:shaking: See the picture above. Do you even understand what anti-squat means and what the actual numbers represent???

So again, are you still saying it is all antisquat? How do you explain my rig climbing so well with high AS?
I don't believe your 3 link had high AS..... High is not 100%... 100% is neutral. If you can provide your old 3 link numbers we can discuss facts intelligently. Don't BS me that you do not have the numbers written down...

Still think VS at the frame makes no difference? Have you experienced the difference in the real world?
The vertical separations changes the AS and affect the changes in geometry with travel........ There is not some other magic, non explainable thing going on.

Are you joking here??? Please go and try and understand the concept so we can have an intelligent discussion.:shaking: See the picture above. Do you even understand what anti-squat means and what the actual numbers represent???


I don't believe your 3 link had high AS..... High is not 100%... 100% is neutral. If you can provide your old 3 link numbers we can discuss facts intelligently. Don't BS me that you do not have the numbers written down...


The vertical separations changes the AS and affect the changes in geometry with travel........ There is not some other magic, non explainable thing going on.

lol. I was trying to catch you on wheelbase but you didn't fall for it. Well played. I have the old 3 link numbers and the new ones. I don't have radius arm ones, I did that for fun a long time ago.

Over 100% is high antisquat. 100 is not neutral. I know why you are saying that, because the forces cancell eachother, but it's 100%. Neutral is neutral. My first 3 link had over 100% antisquat. That's what I mean when I say I run high as. I will post it tonight.

Now on to the whole damn point, read this several times before you respond. I have no disagreement that VS can change AS and have no disagreement the VS will change the way AS changes as suspension travels. Okay, you with me? Now, as you climb a wall, there is no change in suspension geometry. So discard that part. Now, what I am saying very clearly is this: if one suspension has little or no VS and the other has a lot of VS, both the same AS, the one with no VS will unload before the other.

Now on to the whole damn point, read this several times before you respond. I have no disagreement that VS can change AS and have no disagreement the VS will change the way AS changes as suspension travels. Okay, you with me? Now, as you climb a wall, there is no change in suspension geometry. So discard that part. Now, what I am saying very clearly is this: if one suspension has little or no VS and the other has a lot of VS, both the same AS, the one with no VS will unload before the other.

I do understand what you are trying to get at...I just don't agree....

When you drive up a slope, the acceleration forces that are shown in the link calculator still hold, but only for the portion of power used to accelerate, so it mainly controls the dynamic behavioral change of the forces in the suspension, such as the hopping mentioned earlier.

The static weight on the tires if stopped is ONLY the CG position and wheelbase and is not affected by the suspension at all.

The static forces due to being on an angle and how this affects the spring forces is a different subject. This needs to look at the axial location of the center of gravity, tire size, wheelbase and suspension geometry. I think this is the part of the equation you are trying to explain. The location of the instants centers is still what controls the changes in static spring forces. This is where really low anti-dive (front) and really high ant-squat (rear) get you into trouble as the static unloading happens early in the tilt. You need to draw the specific suspension in question and calculate the static forces to see the complete range of effects as you tilt the vehicle further.

Great. Let's agree to disagree then. It doesn't look like either of us are going to change opinions.

I disagree with both of you. But, I have no idea what I'm talking about. :flipoff2:

On a side note: how do you guys feel about the RTE A-arm extension? I've been under this damn truck so much lately, I can't help but stare at shit. It's been on there for years and I have no negative reports on it. It just seems to put that joint at an odd angle.

I owned a cherokee prior to this and it was 4 linked in the front. After driving the rover it was very obvious that the front end unloaded with a lot more force when encountering an obstacle on an uphill with any speed at all. I would imagine a 3 or 4 link setup with litlte or no verticle seperation on the frame side would act just like radius arms. Just my 2 cents. Could the angle of the upper arms have more effect on the unloading versus the actual frame seperation? Flat unloads easier versus some downward angle? IDK.

Lego anyone?

I think I stepped in shit

these are the numbers i am looking at having with my front 3-link setup... i think froom all my research that it will work just fine what do you guys think? and sorry for bringing up a 1 month old thread.....p.s. this is on a 89 cherokee automatic with hp44 front and 9inch rear


3 Link Calculator v1.0 - Vector-Based with Graphical Worksheet Add-In
Vehicle Specifications:
Wheelbase 109.0 in
Tire Diameter 38.00 in
Tire Rolling Radius 19.00 in
Sprung Mass CG 'Z' 45.00 in
Weight 4,500 lb
Suspension Geometry: Geometry Summary:
Upper Link x y z Anti-Squat 94.28 %
Frame End 38.00 10.00 28.50 in Roll Axis Angle 0.15 degrees roll oversteer
Axle End 0.00 10.00 25.12 in Roll Center Height
24.63 in
Lower Links x y z Instant Center X- Axis 83.66 in
Frame End 37.50 3.50 23.37 Instant Center Z- Axis 32.56 in
Axle End 3.00 21.00 16.50
Pannhard Bar x y z
Frame End -2.00 -16.00 31.00 in
Axle End -2.00 16.00 18.25 in