What should my caster angle be?

[Montana TJ]

Hi there,
Any updates on this thread? Super curious to hear how it turned out. I have an 05 TJ with a 2 inch lift and I’m getting some shimmying once engaged in first gear. All other gears seem fine. Curious to know if my current castor @ 4.7 is what’s driving this issue.

Thanks!!

I’m on 31’s right now

 

[astjp2]

Is caster if 3.6 to 4.0 ok with 35” tires ?

Pinion angle is more important that castor angle. Semi trucks with straight axles are as low as 2 degrees with 37” tall tires. Your wandering might be due to toe being off and the wheelbase

 

[Sean B]

Hi there,
Any updates on this thread? Super curious to hear how it turned out. I have an 05 TJ with a 2 inch lift and I’m getting some shimmying once engaged in first gear. All other gears seem fine. Curious to know if my current castor @ 4.7 is what’s driving this issue.

Thanks!!

4.7 seems sorta low, especially with 2 inch and 31s, I would think you could get better than that. What most people are doing is if you have adjustable arms slowly increase the caster until it drives right or until you get driveline vibrations. Then back off a little until vibrations go away. It’s a compromise between pinion angle and caster. On mine I was able to get to just under 5.5 with 4 inch lift and 35s.

 

[Old Jeepin Cowboy]

I’ve got 33” tires on a 4” lift. I’m having a bit of a wandering issue in - mainly on 2-lane roads that aren’t as “flat” as the main roads. I have to work a little harder on these smaller roads to keep it in the lane. It seems to really react to the angle of the road and want to pull one way or the other. It’s fine running around town on the wider roads, but when I get on the backroads, it’s a little iffy.

Anyway, I’m not sure what my current caster angle is, but I’m wanting to get an alignment done and tell them specifically what to set my caster at. From other threads I’m thinking it needs to be around 6 degrees. Does that sound correct?

I doubt your wandering is a caster issue. Wandering on pavement is just a bag full of jelly beans aka multiple sources.

Weak front shocks
Tire psi unequal
Steering shock weak
Uneven tire wear
Caster

 

[Montana TJ]

4.7 seems sorta low, especially with 2 inch and 31s, I would think you could get better than that. What most people are doing is if you have adjustable arms slowly increase the caster until it drives right or until you get driveline vibrations. Then back off a little until vibrations go away. It’s a compromise between pinion angle and caster. On mine I was able to get to just under 5.5 with 4 inch lift and 35s.

Thanks for the advice!! I’ll give it a shot.

 

[BDP]

We don't do it that way ever. There is nothing that says that both upper control arm mounts are in exactly the same spot.
If you set arms dimensionally the same, that can easily put them in a bind fighting each other.

Remove the bolt from one end of one upper. Adjust the other upper to set pinion/caster and leave the bolt at one end loose.

When you are happy with the adjustment, jack up the front side of the axle to relieve the pressure on the loose bolt so you can turn it easily. When that is done, adjust the other upper arm over until you can get the bolt in, that now sets the load on both uppers the same and they aren't fighting each other.

This assumes one is smart enough to do all this on level ground without the vehicle leaning over to one side.

We don't do it that way ever. There is nothing that says that both upper control arm mounts are in exactly the same spot.
If you set arms dimensionally the same, that can easily put them in a bind fighting each other.

Remove the bolt from one end of one upper. Adjust the other upper to set pinion/caster and leave the bolt at one end loose.

When you are happy with the adjustment, jack up the front side of the axle to relieve the pressure on the loose bolt so you can turn it easily. When that is done, adjust the other upper arm over until you can get the bolt in, that now sets the load on both uppers the same and they aren't fighting each other.

This assumes one is smart enough to do all this on level ground without the vehicle leaning over to one side.

How do you set up the lower control arms before you do the uppers?

 

[mrblaine]

How do you set up the lower control arms before you do the uppers?

Tape measure and square the axle to the frame.