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Yea....I get that part of it.........but I guess my main question is do the low A/S numbers that work for crawl'n and haul'n in the rear apply to the front?
If this is completly wrong.....I would love to hear the right answer:D
a predictable and well rounded suspension works better than one that has had the numbers polished over and over. once the geometry is close to what works for a certain terrain or style of driving then shock tuning can make more of a difference than looking for the perfect numbers.


$0.02
 

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Okay....so ive read throught this thread about 10 times and countless other pages of suspension theory.......my question is do the same theorys apply to the front ???? Do the lower A/S numbers work for the front ?? Sorry if this has been coverd........
Take a look at post #58 on this thread. A search on anti-dive also turns up quite a bit and so will wheel recession.
Here are a few that come up with my name and anti-dive
http://www.pirate4x4.com/forum/showpost.php?p=6390107&postcount=25
http://www.pirate4x4.com/forum/showpost.php?p=6351306&postcount=56
 

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just read this thread and it seems that thoughts on link suspension have changed in recent years. and things are being answered more deffinitively with logic and reason behinde it. where as years ago answers were more "his buggy has these numbers and it works wicked good so that's what you need to shoot for!". is there any way we can add some front suspension tech, get rid of a little BS in this thread and turn it into an evolving sticky? i want to thank all the contributing members in this thread
 

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Discussion Starter #105
I'm definitely going to discuss more about the build I'm working on... and I'm about to start a second chassis that will be VERY similar, but be 4 linked both ends with the exact same rear geometry. It will be interesting to compare the two.


I agree that a good discussion about front suspension and what to look for to get a good balanced F/R setup that works together. Some of it has been touched on in this thread already concerning Roll Centers F/R..


-Tim
 

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I guess I'll jump in with a front end question then.

Triaged, How do I calculate a trailing arm front end on a Jeep TJ, XJ, ZJ (like RE, Clayton, or similar), use the 3 link calculator?

I've been measuring up the different manufacturer's suspension as we install them at the shop to try and get a baseline for why some handle the way they do. If anything, it'll give us some good ideas on how to make them work better for the customer.

So far the rears have been interesting in that they all have big anti-squat, some in the 150+ range. 'Course this is mostly due to the lack of separation of the links at the frame.
 

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For the most part...Yes, you should use the 3-link calculator for a Jeep front end (leading link FWIW). 4 Links + Panhard (what OEM's call a 5-link) is an over-constrained suspension and isn't so simple to analyze and ignoring one link is the easiest way to figure out what is going on. To get anti-dive multiply the anti-squat output by the %'age front brakes (or just ignore it like many people do).
 

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Discussion Starter #109
You don't know how many PM's I've gotten about that....

It's a quick and dirty photochop.. I think it's cool to see both on one page just to help see whats going on in both ends at a glance. It would be nice to have an analyzer that did both on one page and you could see it all at once...:smokin:

-Tim
 

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Triaged, How do I calculate a trailing arm front end on a Jeep TJ, XJ, ZJ (like RE, Clayton, or similar), use the 3 link calculator?
For the most part...Yes, you should use the 3-link calculator for a Jeep front end (leading link FWIW). 4 Links + Panhard (what OEM's call a 5-link) is an over-constrained suspension and isn't so simple to analyze and ignoring one link is the easiest way to figure out what is going on.
Just to be clear, I am asking about calculating the aftermarket trailing arm front suspensions like RE, Clayton and others long arm kits where they tie in the upper control arms to the lower control arms, basically making the suspension a trailing arm with panhard.



By tieing the top arms to the lower arms, it is basically the same as the early Ford, coiled Land Rover and FJ80 Land Cruiser front trailing arm suspension, yes?
 

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How much anti-squat do you think this thing has?


Sounds like it has enough traction and torque to break the trans (looked like it was in 2nd gear when they passed me at RM126).
 

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Trail Braking

Has there been any discussion about trail braking? That is: On the gas and on the brake slightly at the same time. This can change suspension action significantly, and use it regularly.

I have a short wheelbase flat fender running a older corvette style independent rear. Built in the mid 60's, and modified for strength over the years, it does pretty good in the fast sand. There is one short trailing arm (24") ponting up at about 7'. Antisquat is almost non existant, as when trying to start on dunes. actually starting up in reverse works better. When launched, landing is always better with slight braking and on the gas. I think this locks the suspension somewhat adding more antisquat. Since there is only about 7" total travel it needs the extra resistance...I believe it helps when broadsliding also.

Trail braking is also used on offroad motorcycles to temporarily increase rear wheel control on acceleration.

Personally, I like some antidive in the front also. Just more control over the suspension when you might need it.

At Moab, with an automatic, I am always more comfortable with trail braking the climbs. It seems to stop side-to-side tippiness...(With minimal traction of the front wheels, trail braking the front tends to keep the front down on climbs...the way I am set-up now with leafs on the front)

Consider these old school comments, but seem to work, or be a crutch for what I've got.

We front linked a couple flats in the mid 70's and also found that when going fast in the desert/dunes, the force applied by brakes on the front end can be considerably more than even the rear under acceleration. The top bar of a three link (front) will get stretched considerably! Go Big and quality on the heims and mounts!!!! There is no safety factor on the three bar. Something that the four bar has (With the trade off being twisting the front axle, or bending the bottom link as in the RE arm.)

I am also looking for the "perfect" three bar + set-up..with saginaw steering.
 

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Discussion Starter #115
Has there been any discussion about trail braking? That is: On the gas and on the brake slightly at the same time. This can change suspension action significantly, and use it regularly.

I have a short wheelbase flat fender running a older corvette style independent rear. Built in the mid 60's, and modified for strength over the years, it does pretty good in the fast sand. There is one short trailing arm (24") ponting up at about 7'. Antisquat is almost non existant, as when trying to start on dunes. actually starting up in reverse works better. When launched, landing is always better with slight braking and on the gas. I think this locks the suspension somewhat adding more antisquat. Since there is only about 7" total travel it needs the extra resistance...I believe it helps when broadsliding also.

Trail braking is also used on offroad motorcycles to temporarily increase rear wheel control on acceleration.

Personally, I like some antidive in the front also. Just more control over the suspension when you might need it.

At Moab, with an automatic, I am always more comfortable with trail braking the climbs. It seems to stop side-to-side tippiness...(With minimal traction of the front wheels, trail braking the front tends to keep the front down on climbs...the way I am set-up now with leafs on the front)

Consider these old school comments, but seem to work, or be a crutch for what I've got.

We front linked a couple flats in the mid 70's and also found that when going fast in the desert/dunes, the force applied by brakes on the front end can be considerably more than even the rear under acceleration. The top bar of a three link (front) will get stretched considerably! Go Big and quality on the heims and mounts!!!! There is no safety factor on the three bar. Something that the four bar has (With the trade off being twisting the front axle, or bending the bottom link as in the RE arm.)

I am also looking for the "perfect" three bar + set-up..with saginaw steering.

I'll take a stab at this...

Using your brakes can significantly affect weight transfer through the chassis and definitely affect handling when you're on the edge of resistance both on and off road.

However, I think what your noticing (in your rig) is a side affect of the geometry in your rear suspension. The older Vette stuff had more AS than you think, If you front brake only and apply some power on the pavement, I bet your rear end will "stand up" at almost the top of it's travel and get hard as a rock. When you apply the brakes and power in a drift your affectively stiffening up the rear end... also when climbing, the same thing is happening. Your just making the rear end jack up and get stiffer making you feel like your loading the front tires more and seat of the pants stability from the stiffer spring rate... all of this is being created by you loading the links (with the brakes) and creating additional AS. I don't think you'll see this happen in every setup, and It's not something I would intentionally design in. I think it's just something you've learned about your setup that helps it work. With the fairly limited 7"of travel, even at the top of the stroke your axle is not trying to walk under the rig like it would with long travel suspension.

Now for the bikes... I know the uni-link Hondas from the 80's would squat in the rear when you drug the brake. As far as increasing traction and or giving you more control while accelorating... My guess is you had more control cause you were going slower.

Unless being used as a crutch for suspension design, brakes should be reserved for slowing down and weight transfer... unless you don't have lockers, then you can use the E-brake to make your open diff think it's getting equal traction. "pull your e-brake to the second click and crawl it":flipoff2:

-Tim
 

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Now for the bikes... I know the uni-link Hondas from the 80's would squat in the rear when you drug the brake. As far as increasing traction and or giving you more control while accelorating... My guess is you had more control cause you were going slower.
I would like to understand this phenomenon better. It really works and it's not because you are going slower! Very talented moto guys will drag the rear brake when the corner has accel/braking bumps to smooth the rear suspension and allow the bike to track and accel FASTER!
I’d agree with the feel that the brakes help on all these situations and it crosses over to rock crawling really well. When the course has major “double whammy’s” if you hold some brake, the car would not bounce as much on the face of the hit.

So what causes this to work and if it works…should we be setting the car up to have this naturally instead of induced by adding brakes?
 

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It took a while to digest Tims' and Jason's remarks, and trail braking has been a confirmed tool for offroad (rough) racing or playing.

I think there are times when you WANT to bind or move the suspension. This allows you to set springs and shocks to a "neutral" zone that takes 80-90% of the track/trail/course. The trail braking, standing on the gas, and pitching the vehicle all contribute to that last 10% of control necessary to keep the vehicle going fast without endoing, over sliding, etc. Brakes are not simply for scrubbing speed. It seems like they can set-up lots of things. Next time, out going fast, I will have to try and relate what I am doing with the brake in the 4x4. I am sure it would be different in a 2x4 where you are not as loose on the rear end.

I learned about and use trail braking on motorcycles...learning to go fast. I don't notice doing anything different in the 4x4, but may be. For instance: It seems like going into a major compression/up jump I will trail brake to prevent the rear from totally collapsing, bottoming, and launching me end-over-end. On landing, trailbraking at impact and on the gas tends to retard compression and then rebound and bring things back under control.

For some reason I like brake induced anti-dive on the frontend....maybe for the same reason if I land front wheel first??? Short brake...on the gas. Jumping off of something I surely wouldn't want the front to just collapse from soft spring or shock settings. At full droop when the shocks and springs are at their lightest, antidive can be used to real advantage.

When going through whoops, I know you have to be on-the-gas until your balls are not big enough for the speed. I am not sure if this has to do with antisquat or trying to keep the front end light and just kissing the tops of the whoops...??? Probably an explaination here, but have just done it from learning, watching and experience.

Still coming from old school. I have no 4x4 experience with long travel, but think that sooner or later (the faster you go) the same principles will return...??? It has been that way with MC's.

I'll bet it is taught and discussed in advanced offroad MC classes now. If you look at most of the successful fast learner 4x4 pilots, they were accomplished bikers. They know more than just reading trail. As Jason says. There is something here that needs to be considered.

PS. Got lockers, and believe Tim is right about Corvette rear jacking, but once the tires slip, or accelerate, it collapses quickly.

Which reminds me also of Moab (going slow). Locals will comment about clicking out of full lock in the front when going up steep inclines. It helps keep the front down. (this comment could be meant for TJ's?????)

Thanks for getting us talking. Need some one to explain the stuff in my pants.
 

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On landing, trailbraking at impact and on the gas tends to retard compression and then rebound and bring things back under control.
This is a perfect example of the problem with low anti-squat numbers! I've programed my brain to hit the gas on the landing from Motocross. When I did this in my buggy, the rear would bottom out. If I landed in a neutral throttle position the car would absorb the impact. Going through whoops is just a fast sequence of jumps. Hopefully the new rear suspension geometry setup will fix this because now that I know you can't fix this with valving and still have the smaller bumps absorbed, you must keep it up closer to neutral anti-squat.

I'll have to play with the brakes more, they are so good now with the large rotors you can really maximize control.

ISDTBower- you will love going for a ride in the new buggy, it's the closest thing to a dirt bike with a roll-cage! couple weeks and it's back together!
 
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