Here is a strange one:

I have welded the spiders in my rear 70 HD, and built a triangulated 4 link under the rig to mount it. Flexes great, no lift or squat on acceleration, all seems well, until..............

I turn.

It is like body roll, but it even happens at .0000001 mph. The axle binds up while turning at any speed since there is no differentiation, and it leans pretty substantially.

I have seen other triangulated 4 link rigs with spools do this, so I am not alarmed. As soon as I hit the trail, I suspect it will be like the others and be very stable, but on the street, it's just plain goofy to drive.

The good news is, I don't need to drive it on the street. :D

The question is, is this normal or is there something I miscalculated? Roll center appears fine if I am calculating it properly, instant center is about 4' ahead of the lower arms mounts...all work well, it just binds up in turns and leans. If I pull an axle shaft , it stays flat in turns.

Do I ignore this or did I miss something?

Ed

If the WB is short, this is normal. You have a CJ, so I'm guessing you do.

My buddies 01 TJ on 35's w/ a detroit in the back can pull his frt driverside tire over a foot off the ground when he turns hard left from a dead stop. Pretty funny reaction from the passerbys. :eek: :flipoff2:

Mine did it with leafs all around so I'd say it's normal. Just a characteristic of a spooled rear and soft suspension. Never even noticed it once I hit the trail.

How far (in the side view, Y axis) away is the roll-axis from the CG plane?

you don't even need a locker to pull up the wheel a foot on a left turn in a TJ w/ stock susp. you can just get it extra high w/ a locker. although, after I went to 4-link it is not quite as easy to do. still get some roll though, you should be OK.

I'll tell you a funny story if you promise not to tell anyone.

When I was building my truck I was waiting for shocks and things to come in, so I decided to run have the exhaust put on. I didn't have shocks or limiting straps at the time and my coils were just sitting on the axles with tubing in the center to keep them centered.
When I got to the muffler shop, of course everyone comes out to see what the hell it is, so there are about 8 or 9 guys standing around looking. I backed it off the trailer and turned a little to head towards the garage.
Well, it had done what you are talking about a few times in the driveway, but I had only driven it a few feet till now. When I turned in the muffler shop parking lot, of course, it did the hike the leg thing. I thought to myself: If I just blip the throttle a little the tire will spin and it will settle down.
Uh...no. I blipped and it jumped off the frame completely. In other words, I basically rolled it in the parking lot. The only coil still seated was the passenger front.
About 6 guys picked the front up and got the driver side coil in and we used an engine hoist to raise the rear and get the back coils in. Needless to say, that was about the most embarrasing thing I ever did.:emb2:

ED

Russ had this problem with his 8.8 welded

i think that a sway bar for street driving would calm it down

Originally posted by 350 Samurai
I'll tell you a funny story if you promise not to tell anyone.

When I was building my truck I was waiting for shocks and things to come in, so I decided to run have the exhaust put on. I didn't have shocks or limiting straps at the time and my coils were just sitting on the axles with tubing in the center to keep them centered.
When I got to the muffler shop, of course everyone comes out to see what the hell it is, so there are about 8 or 9 guys standing around looking. I backed it off the trailer and turned a little to head towards the garage.
Well, it had done what you are talking about a few times in the driveway, but I had only driven it a few feet till now. When I turned in the muffler shop parking lot, of course, it did the hike the leg thing. I thought to myself: If I just blip the throttle a little the tire will spin and it will settle down.
Uh...no. I blipped and it jumped off the frame completely. In other words, I basically rolled it in the parking lot. The only coil still seated was the passenger front.
About 6 guys picked the front up and got the driver side coil in and we used an engine hoist to raise the rear and get the back coils in. Needless to say, that was about the most embarrasing thing I ever did.:emb2:

That's hilarious.......thanks for sharin'!!

350 samurai,
Thanks for starting my day. I doubt Frankie Finland can top that one. :D
:D

note to self

finish jeep suspension before driving

:D

im running my stock fj-40 springs over my chevy axles with a welded diff.. when i turn it does the exact same.. my passengers get the pucker factor a bit, but hten they get used to it. 350 sami thats hilarious. do you have any pics LOL.. i bet you made sure there wasnt any cameras around . so your first roll over with the new ride wasnt even on a trail.

That is funny! now I know why I like my springs attached at both ends!

a torsion style sway bar does wonders for that odd little trick

I bet theres more than a few people here that almost rolled in parking lot, hell a few people I know did it on there cherokees.

This idiot guy I know...well my friend was driving w/ him in his Cherokee w/ about 8" of lift on 35"s. Kent (my friend) is all...damn man you don't know how to drive your cherokee. Hes like what are you talking about. Well they work in the automall so they take this basically right hand turn (from lead hill into the automall for all you sacramento/roseville people). He decides to show off his skills for Kent and (FLOORING IT ON THIS TURN) ends up getting his cherokee on ONE wheel, which bottomed out into the wheel well effectively stuffing it. Now Kent won't drive w/ him anymore. I wish I would have seen it.

Now Kent has gotten his Cherokee on 2 wheels countless times while driving around in Roseville...but he enjoys that for some reason.

Any other stories of rolling on Paved roads? :flipoff2:

it sounds like you have figured everything out but lifting the inside tire is often asocited with jacking (your link angles are too steep). It causes the power to lift the body so when you go around a corner it really lifts the inside tire. I know "other people" on this board that have that issue because their links are too steep. What is your link angle and maybe you should post a side pic of your rig with the suspension showing

I did the same thing just the other night. Raised the front inner tire off the ground about 1 foot. I basically have a stock TJ with just a 4" lift and the rear is locked up. It was kinda funny.

TRD, so I assume that is why it is harder for me to do now since I went to the 4-link (long arms) which effectively reduced my link angles. makes sense.:idea:

lifting tires with TJs is old news, lock the rear, and hit the gas when turning left.... The real trick is to see how far you can carry it.... :flipoff2:

left turns across 4 lane wide intersections are the best !!!!


-yag
EX. TJ owner

Originally posted by TRD
it sounds like you have figured everything out but lifting the inside tire is often asocited with jacking (your link angles are too steep). It causes the power to lift the body so when you go around a corner it really lifts the inside tire. I know "other people" on this board that have that issue because their links are too steep. What is your link angle and maybe you should post a side pic of your rig with the suspension showing \

Working on the pic's.

Lower links 17 degree angle, 44.5" long

Upper links 13 degree angle, 26.75" long

Pics when the damn camera will work. What pics I do have are here:

http://www.rocktaxi.com/rock%20taxi%20current%20project.htm

Ed

Rock Taxi, you need to make your pics smaller on your link. Some are over 2 and 1/2 megs each. I know the guys with dial ups aren't going to wait 30 minutes for them to load.
By the way, nice welds.

Originally posted by PIG
How far (in the side view, Y axis) away is the roll-axis from the CG plane?

Help me out to make sure I am doing it right. How do I find CG?

Hell, point me to a link with all the formulae. The P.O.S. Sprint car suspension book I have sux. I will recalculate everything again from fresh measurements, just to make sure.

My guessing on CG - Roll Axis 6" below CG. (Roll axis right at upper control arm mounts on axle)

350 sami - which pics did you see that large? Biggest on the D70 and suspension page I saw was 214k - big and being resized, but not 2.5MB. Thanks for the compliment on the welds. I am finally able to do pretty good, even overhead and out of position. 'bout damn time too. :)

Ed

I have the same prob. with my blazer it is spooled in the rear and it leans in the corners. dont have a sway bar on it though.

OUT OF ALL THESE POSTS AND NOBODY ANSWERED.ITS NOT THE LINKS.MY LEAF SPRUNG CRUZAH DOES THIS WITH THE REAR LOCKER ENGAGED.WHEN YOU TURN THE TIRES BIND, EITHER ONE CHURPS AND LETS GO OR THE TWISTEING FORCE GOES BACK THRU THE PINION TO THE SHAFT TWISTINT THE TCASE WHICH IS BOLTED TO THE FRAME....THEREFORE YOUR RIDE TWISTS ....

I agree with Ryan, sometimes folks think too hard.

You already said removing one rear axle shaft makes the problem go away. Removing a shaft doesn't change your link angles, :smokin: so the issue lies elsewhere.

Think about it, turning corners the outside tire is going to rotate faster than the inside tire. If you're spooled (or locked and give enough gas to engage the locker) in the rear, the tires are going to rotate the same rate no matter what. So, either the inside tire barks when turning, or the differentiation is sent up the drivetrain- resulting in twisting the rig and lifting a tire.

We knew that, just forgot to say it.:D

Originally posted by 71RCKCRZR RYAN
OUT OF ALL THESE POSTS AND NOBODY ANSWERED.ITS NOT THE LINKS.MY LEAF SPRUNG CRUZAH DOES THIS WITH THE REAR LOCKER ENGAGED.WHEN YOU TURN THE TIRES BIND, EITHER ONE CHURPS AND LETS GO OR THE TWISTEING FORCE GOES BACK THRU THE PINION TO THE SHAFT TWISTINT THE TCASE WHICH IS BOLTED TO THE FRAME....THEREFORE YOUR RIDE TWISTS ....

wrong answer.

it does it with leaf springs if your pinion is rotated up. it always twists your rig when going around a corner becasue of the binding. what makes you lift a tire are your link angles.

when you rotate your pinion up the effective link angle goes up.

rock taxi- your links are too steep. 15 is absolute max with out spool, with it i would not go over 10 (trail and error)

what is happening is the plane in which the moment caused by the binding is being raised up to a higher angle so rather than just left to right twisting you now have a vertical twist too. If you get too much verticle twist you get jacking.

i would post pics of how it works but i don't have a star.

it does it with leaf springs if your pinion is rotated up....



YEAH ..WHAT DOES THAT HAVE TO DO WITH THE WIERD FORCES.MY CAMARO USED TO DO IT A LITTLE WITH THE WELDED SPIDERS.THE SUSPENSION WAS STIFF SO IT WASN'T TOO BAD, AND THE PINION WAS A FEW DEGREES UNDER THE DSHAFT,NOT POINTED UP.:D

OK...SO WHY DID MY CAMARO DO IT.:D

ITS NOT THE LINKS:flipoff2:

Originally posted by 71RCKCRZR RYAN
it does it with leaf springs if your pinion is rotated up....



YEAH ..WHAT DOES THAT HAVE TO DO WITH THE WIERD FORCES.MY CAMARO USED TO DO IT A LITTLE WITH THE WELDED SPIDERS.THE SUSPENSION WAS STIFF SO IT WASN'T TOO BAD, AND THE PINION WAS A FEW DEGREES UNDER THE DSHAFT,NOT POINTED UP.:D

OK...SO WHY DID MY CAMARO DO IT.:D

ITS NOT THE LINKS:flipoff2:

I misstated it before for simplicity. If your spring perches are not on top of the axel (you added shims to get pinion to point up) or your axel comes that way (camaro?) then that will cause the moment in the vertical dirrection. it is the links, think about it, how else could you get a verticle moment like that, you can't. What happens when your links get too steep, you get jacking. your camaro didn't lift a tire because the spring perch was not pointed up as much as someone would on a 4x4.

what is the problem: jacking

what causes jacking: link angle

does anything else cause jacking (moment in verticle dirrection): Not that is blatently obviouse in this case

cause: link angle

solution: lessen link angle

YOUR RIGHT ABOUT THE JACKING...THE LINK ANGLE PUSHING ONE SIDE UP. BUT THATS NOT WHAT THE QUESTION WAS.....IT WAS JUST LEANING. WITH SQUISHY SUSPENSION I DONT THINK IT MATTERS IF ITS LINKED OR SPRUNG OR WHATEVER...WITH THE TIREW BINDING ITS GANNA LEAN....

ITS NOT THE LINKS:D :flipoff2:

ITS THE LOCKED UP REAR AND SQUISHY SUSPENSION

Originally posted by 71RCKCRZR RYAN
YOUR RIGHT ABOUT THE JACKING...THE LINK ANGLE PUSHING ONE SIDE UP. BUT THATS NOT WHAT THE QUESTION WAS.....IT WAS JUST LEANING. WITH SQUISHY SUSPENSION I DONT THINK IT MATTERS IF ITS LINKED OR SPRUNG OR WHATEVER...WITH THE TIREW BINDING ITS GANNA LEAN....

ITS NOT THE LINKS:D :flipoff2:

ITS THE LOCKED UP REAR AND SQUISHY SUSPENSION

I agree that just having a spool causes some leaning but not enough by it's self to lift a tire. I believe the reason he is lifting a tire is because of jacking not just because he has a spool. both work together to create his situation and the best solution (for rock crawling) is to lessen the link angle.

The tires never lift, but it does lean. Throttle input will make it worse, but not apprecialbly.

It is fun to watch y'all discuss this though. :)

Ed

if i was you i would lower my link angle. it is unsafe to have a vehicle that roll whenever you turn and hit the gas. It could also cause you to roll easily off-road.

I am inclined to agree, but what are your thoughts on link angle change, while my instant center would go bonkers because the links would never have an intersection point, what about moving just the frame end of the lower link to change it's angle?

Ed

you are going to have to change the geometry. If i was you i would push the axel back but if you don't want to do that you are going to have to go with longer links (if you want them to mount to the frame). I wouldn't move just the lower links because you upper links are also over the limit as far as runnign with a spool is concerned.

I would go with as low of an angle as you can get with still having a resonable amount of anti squat. It is just one of those situations where you need to sit down and make a list of priorities and figure out what you think is acceptable then try to design something within those constraints.