Cross caster

DLA

New member
This is my first post, kind of looking for any knowledge you might have on this subject. I bought a 2016 sahara with 36k on it back in May, which was unmolested at the time. I lifted it 2.5 inches front and rear with a spacer kit. I centered the rear axle with a relocation bracket, and the front axle with an adjustable track bar. I resolved a flighty steering problem with control arm lowering brackets. I put 33x10.5 wrangler adventure kevlar tires on the stock wheels with 1 inch wheel spacers. I drive the jeep on the highway every day, I have a 21 mile commute to work - the lift is primarily for looks and it looks killer, I like the pizza cutter aesthetic I get from the 10.5 width, sort of vintage looking.

I have an ever so slight pull to the left, noticeable at speeds above 40. Tire rotation has no effect on it. I have measured my thrust, hubs on both sides are exactly 95 3/8 inches, so that seems fine. Axles are centered to within 1/8". Popped my front driveshaft off and measured the angle of the input to the front diff, 2.3 deg. If I'm correct, my pinion angle/caster is 3.7. I measured the angles at the top of each upper ball joint. Driver side is 3.7, passenger side is 5.25.

In my estimation, this is cross caster and is excessive - and would cause a pull to the left which is what I feel. I am bringing her to a shop on Wed morning to get readings off the alignment rack, and the shop will not be adjusting or touching anything.

My guesses - control arm bushing in the axle is bad, control arm bracket tolerance is off, or the manufacturing of the axle is off. I believe FCA shoots for a half degree of cross caster to counteract a pull to the right from the crown in the road, but they are a little loose on how accurate that is, but mine is way off.

I have ordered new axle bushings and a set of adjustable uppers and lowers for the front. I know I cannot dial in cross caster, but my thought is that if I increase my caster from 3.7 to 5 or 6, the effect of cross caster would be less influential.

Any part of this sound wrong?
 

JimLee

Active Member
I'm at 6.1 degrees drivers and 6.3 passenger, drives great with almost no road crown pull unless the road has a very noticeable crown. I'm driving a JL but i'm sure a lifted Jk would benefit from the extra caster as well.
 

wayoflife

Administrator
Staff member
This is my first post, kind of looking for any knowledge you might have on this subject. I bought a 2016 sahara with 36k on it back in May, which was unmolested at the time. I lifted it 2.5 inches front and rear with a spacer kit. I centered the rear axle with a relocation bracket, and the front axle with an adjustable track bar. I resolved a flighty steering problem with control arm lowering brackets. I put 33x10.5 wrangler adventure kevlar tires on the stock wheels with 1 inch wheel spacers. I drive the jeep on the highway every day, I have a 21 mile commute to work - the lift is primarily for looks and it looks killer, I like the pizza cutter aesthetic I get from the 10.5 width, sort of vintage looking.

I have an ever so slight pull to the left, noticeable at speeds above 40. Tire rotation has no effect on it. I have measured my thrust, hubs on both sides are exactly 95 3/8 inches, so that seems fine. Axles are centered to within 1/8". Popped my front driveshaft off and measured the angle of the input to the front diff, 2.3 deg. If I'm correct, my pinion angle/caster is 3.7. I measured the angles at the top of each upper ball joint. Driver side is 3.7, passenger side is 5.25.

In my estimation, this is cross caster and is excessive - and would cause a pull to the left which is what I feel. I am bringing her to a shop on Wed morning to get readings off the alignment rack, and the shop will not be adjusting or touching anything.

My guesses - control arm bushing in the axle is bad, control arm bracket tolerance is off, or the manufacturing of the axle is off. I believe FCA shoots for a half degree of cross caster to counteract a pull to the right from the crown in the road, but they are a little loose on how accurate that is, but mine is way off.

I have ordered new axle bushings and a set of adjustable uppers and lowers for the front. I know I cannot dial in cross caster, but my thought is that if I increase my caster from 3.7 to 5 or 6, the effect of cross caster would be less influential.

Any part of this sound wrong?
Any chance you're running a set of Nitto Trail Grapplers? If so, what you're experiencing is most likely being caused by radial pull.
 

DLA

New member
No, I have the good year wrangler adventure kevlar tires, and I've done several rotations to try to isolate tire pull and while it could be the tires in general it's not any specific tire or pair of tires as the rotations have had no effect. I will say though, that all of my wheels do not stand up by themselves - they are all heavy toward the outside which is something I've never seen before on any vehicle. What I mean is when off the jeep they must be leaned back toward the inside or they will fall over to the outside. This is weird, but I have no vibration at any speed to indicate poor balance and I now have 46k so almost 10k on these tires and the wear looks fine.
 

wayoflife

Administrator
Staff member
No, I have the good year wrangler adventure kevlar tires, and I've done several rotations to try to isolate tire pull and while it could be the tires in general it's not any specific tire or pair of tires as the rotations have had no effect. I will say though, that all of my wheels do not stand up by themselves - they are all heavy toward the outside which is something I've never seen before on any vehicle. What I mean is when off the jeep they must be leaned back toward the inside or they will fall over to the outside. This is weird, but I have no vibration at any speed to indicate poor balance and I now have 46k so almost 10k on these tires and the wear looks fine.
The Trail Grappler was just an example. Radial pull is common with a LOT of tires. Were you feeling this pull with stock tires?
 

DLA

New member
I'm going to say no, but I only drove the Jeep in stock form for a week or so. I did the lift and new tires at the same time. My pull is very slight, it could be radial pull. Tomorrow morning I will have alignment rack numbers which will help me verify that I can measure correctly, and that I have set things up ok. And, adjustable uppers and lowers will be here thursday and a degree or two more caster certainly won't hurt me. I'm not trying to make a cadillac here, just playing with my jeep, and I'm pretty sure I can do something about the pull. That something might just be wearing out these tires and buying a different set.
 

bmkrinne

Active Member
You are correct…The stock separation angle is 6 deg between the pinion and C’s on the stock axle housing. With your pinion angle at 2.3 deg measured on the pinion input flange, your caster should be about -3.7 deg. The flighty feeling is due to the low caster angle. Try moving your upper control arms to the next hole back on the geometry correction drip brackets. This should increase negative caster and reduce or eliminate the flighty feeling. It may also rid you of the slightly left pull due to the centering effect of the higher negative caster.

I don’t have my stock front axle anymore but do remember getting weird caster measurements on top of the ball joints. I always went off of the pinion flange for caster measurements, but with geo brackets you only have limited adjustment.

Did you have to force one of the control arm bolts in when connecting the last joint? If so you may be onto something with the bushings. But before I messed with that I’d try the geo bracket adjustment.
 

BlueRubicon

Caught the Bug
👆what he said...
Wow...the negative caster on drivers side would definitely cause pull left. If you measured both sides the same and your difference is that much, something is out of whack. Make sure when putting CA bolts in, you only snug until setting vehicle down. Torque them under load so as to prevent any bind.
 

DLA

New member
I think you're right about measurements off the ball joints being unreliable. I just got alignment rack numbers this morning. Camber is -.06 each side, caster 3.6 left, 3.8 right - so the 3.7 I measured off the pinion is good. The 5.25 off the ball joint is possibly no good. Toe is .09 left and .14 right for a total of .23. Steer ahead is -.02 and thrust angle is .06. So, I feel like I can align the jeep pretty well which isn't saying much cause it's kinda easy.

Also, I had no problems with installing control arms with the drop brackets. I think I did use a ratchet strap to move the axle a bit, but it was easy and I never had to force any bolt. I may not have jounced well enough before torquing everything down.

I used the top holes on the control arm drop brackets, and I think that's a good suggestion that I try the next hole down. And I guess if that bumps my caster up I don't need the adjustable upper and lower arms which are in the mail right now.

But... I'll probably put those on anyway!
 

bmkrinne

Active Member
Good news on the alignment numbers for your caster. Means your balljoints were causing measurement errors. Go off of the pinion flange and you’ll be Golden! If you are set on the geo brackets, I personally wouldn’t put the adjustable control arms on but it’s not my Jeep! Haha!! Good luck!!
 

JimLee

Active Member
I'd put the adjustable arms on for no other reason than they are probably beefier than the stock ones (depends on what you got), those hollow rectangular factory tubes don't handle coming down on a rock hard very well, I've seen pictures of a few turned into tacos on some rocks.
 

DLA

New member
I moved my upper arms down a hole in the brackets, now I've got 4.75 deg of caster - see how it feels on the road tomorrow morning. I forgot to look at the driveshaft, I guess what I've done is stolen a degree of angle there but that's probably ok.
 

DLA

New member
Pretty amazing what a degree of caster does. I don't have any pull until I get above 60mph, and then it's reduced and sometimes shifts from one side to the other depending on the crown. I can actually take my hands off the wheel for a bit, or drive with a knee for a bit. I know that seems unbelievable, but I can. One or two miles this morning I thought, I still have pull, but with the added caster the jeep definitely feels like it wants to track straight.

My new control arms arrived - feels like 100 pounds of weight that maybe I don't really need added to my already heavy front end.

Thanks for all the responses!
 

DLA

New member
Bumping this because I still have a pull to the left. I guess I was just too enthusiastic about wanting it to be fixed that I felt it was. I see two possible options, one which I will try today is to increase tire pressure on the left front so it's higher than the right. The other option could be a caster/camber adjustable ball joint on the right to adjust caster individually on that side, reducing it by a half degree which would give me higher caster on the left, and would essentially dial out the built in cross caster meant to counteract road crown. Anybody ever use those?
 

ScottofKSU

Caught the Bug
I have read about addressing this issue by ofsetting the front axle ever so slightly to the passenger side - like 1/2 an inch or less. When you say your axle is squared to an 1/8 inch; which way is it off (i.e., driver or passenger side)? If driver, this may help, if passenger, disregard.
 

DLA

New member
I don't remember, but I can definitely figure that out and adjust the axle position. That's easy and can't hurt, thx!
 

ScottofKSU

Caught the Bug
I'm going to say no, but I only drove the Jeep in stock form for a week or so. I did the lift and new tires at the same time. My pull is very slight, it could be radial pull. Tomorrow morning I will have alignment rack numbers which will help me verify that I can measure correctly, and that I have set things up ok. And, adjustable uppers and lowers will be here thursday and a degree or two more caster certainly won't hurt me. I'm not trying to make a cadillac here, just playing with my jeep, and I'm pretty sure I can do something about the pull. That something might just be wearing out these tires and buying a different set.
Out of curiosity, what adjustable control arms did you go with?
 
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