caster help

[DeftwillP]

I've been trying to track down some loose handling, especially at highway speeds and after hitting bumps. I've replaced all tre's, the tie rod itself with a big daddy, had tires balanced, and today got an alignment. Also of note, rusty's hd tb and mount and bolts are definitely tight.

I know optimal caster is 7*. Right now, I'm at 1.26 left and 1.13 right. This is obviously lower than optimal even though my pinion angle is good. (Funny side note about that: I actually have the drive shaft pulled and zip tied to the lca because I get a funny vibe above 60 after doing my gears. I guess the ujoint is shot.) Is this whats giving me white knuckles and dirty shorts on the highway?

So I'm on 6" inches with rusty's fixed uppers and lowers. Should I shim it? How much per side? Where do I get em etc?

 

[Screech]

The low caster is what is causing your jeep to wander around on the road. Idk if theirs enough adjustment in the stock slots to gain the 6* degrees you need to be perfect but more will be better. That being said I would shim it and use a magnetic angle finder on the ball joint to measure the caster and then have it realigned because your toe will be off. Gojeep has a good write up including dimensions of the shims so you can make your own http://go.jeep-xj.info/HowtoAlignment.htm

 

[cherokee chuck]

I got my shims at a wrecking yard, but I've seen a recent post saying they were available through NAPA stores. Read Gojeeps thread. It took an Aussie to teach me the simple, correct way to adjust camber on my XJ.

 

[RCP Phx]

How about starting w/ some db's or la's!

 

[DeftwillP]

Well, I'd love to go with rk's 3 link but I'm between jobs and $30 or less in shims fits the bill better than something 20x as much. I'm definitely going that path sometime in the future for all of the benefits on and off road. (I'd love to throw on the 3 link, and HD frame stiffeners and shackle relocators all at once for improved ride and capability.)

Thanks for the napa lead though, i'll check it out. I guess I pretty much have to add and measure.

 

[gorman]

For what it's worth I'm currently at just under 6" lift in front and about 6.5" lift in the rear and....wait for this: I'm still running stock upper and lower control arms. Although this is temporary and I'm nearly done with with fabbing adjustable uppers and lower with JJs, the funny thing is my caster with that lift and the stock arms is around 5*. My pinion angle is a little off, but I have no vibrations (and this is with a LP diff). The only thing is my wheels are positioned a little towards the rear of the wheel wells, but with the adjustables I'd probably keep the angles as they are and just move everything forward a little.

I understand that you want to get this done relatively cheaply, but ideally you'd want adjustable control arms to gain that much caster - shims will only adjust a small amount and I don't think you'd want too large a shim in there.

 

[DeftwillP]

Does it take incrimentally more shim for a lifted rig to gain 5 degrees of caster than a stock rig to gain 5 degrees?

 

[DeftwillP]

So I'm using rustys fixed upper and lowers. These are the uppers here:
http://rustysoffroad.com/mm5/merchant.mvc?Screen=PROD&Product_Code=RC-CA121-UV&Category_Code=ARMS
If you notice, it has two sets of holes at the axle end for mounting. If I use the inner set, this would make them approx. 1/2 inch shorter.
Wouldn't this give me more positive caster since I can't seem to find the lca shims I'm looking for

 

[cherokee chuck]

:flame: Read Gojeeps thread. It took an Aussie to teach me the simple, correct way to adjust camber on my XJ.

Sorry, I obviously meant caster, not camber. I guess I need to flame myself!

 

[xjbubba]

Don't understand why your caster is off so much.
Even before installing adjustable LCA's, my caster was ~5* at 6" of lift.
Many vehicles run with 0* caster. Main issue with low caster is wandering, requireing constant driver input.
Shorts-dirtying changes in direction are normally associated with other steering system issues, like loose track bar or bad ball-joints, and tie rod ends.

 

[DeftwillP]

Well it has gotten better since I had the toe set and the tires balanced.
I measured my arms. The uca's are 16" and the lowers are 16.5" if you measure along the curve of the arm. It would seem that these are too close in length to begin with.

Yucca-mans page says at 6", I should have17" lowers and 15.5" uppers. Like I showed earlier, Rusty's fix uca's have two sets of whole and I can use the other set to effectively take 1/2 inch out of the length. It seems like this would work for changing the caster just as effectively as shimming the lca pocket. Thoughts?

 

[gorman]

Yes, it seems your upper control arms are too long. At 6" of lift you will have to compromise on perfect caster for your pinion and vice versa, but saying that you should still be able to end up with caster in the 5* region with acceptable pinion angles - especially if you've got a HP Dana 30 up front.

 

[DeftwillP]

Cool, I'll try moving to the second set of holes. While I need anything special to do this like a come-along or will I be able to just "roll" the axle back a little. The front driveshaft is already disco'd.

 

[nelson7172]

You can also get offset ball joints to correct caster. I think thet are available up to 2*.

 

[DeftwillP]

Yeah, I read that on madxj's page. You can actually get 3.5 degrees by doing offset lower and upper balljoints. At this point though, I just want to try whats relatively free to me to see if that helps. Ultimately, you always want things to be done right, which will yield to me putting on a 3 link or long arms.

 

[DeftwillP]

So, I finally got around to adjusting my axle end mounting points for my fixed UCA's. Night and day difference on the highway now. It's not near as flighty and sensitive to bumps in the road, at least around the interstate here where there is relatively smooth surfaces. Caster is definitely something everybody should take a look at if they've got silly highway steering.