centering rear with adjustable ca's

[James Bond]

is there a trick to this? say i'd like to move the rear to the right 1/4'', is there any magic combination of turns to make to the ca's? there should be some proportion of relative adjustments to get the rear to shift and not pitch or translate fore and aft. any help would be appreciated.

 

[gman415]

Top right bar longer, top left bar shorter. same turns on both sides. It will make the wheel base longer on the right side a VERY small amount. And likewise shorter on the left. Not enough to couse problems.

 

[BMR Sales]

Are you talking left to right or front to back?

 

[James Bond]

Top right bar longer, top left bar shorter. same turns on both sides. It will make the wheel base longer on the right side a VERY small amount. And likewise shorter on the left. Not enough to couse problems.

gman thats what i'd like to avoid. theres some amount that the lowers need to be adjusted to compensate for this. thats what i'm looking for.


bmr, i'm looking for left to right or vs versa.

 

[CutlassRacer]

Set the rear end where you want it with one upper control arm installed in the car. Do some cross measuring comparing the angle of the axle to the frame, straighten out if necessary with the lower control arms, then install the other upper control arm. This needs to all be done with the weight of the car sitting on the suspension. Then install your ARB links with the car sitting at ride height with the driver weight in the car, and then lengthen the passenger side length 1/2 a turn.

 

[James Bond]

cutlass, thanks for the reply. if i disconnect one upper and make the adjustment, won't the rear just pitch? similiar to pinion angle adjustment. seems that i would need to contrain the rear from pitching to make the uca adjustment translate into a left or right motion.

 

[CutlassRacer]

It may pitch a very very slight amount, but not near as much as you think that it would. When you hook both upper control arms up and shorten them both is when you will notice the pinion angle changing. The best advice that I could offer would just be to write down your base settings (all of your control arm lengths), make a single adjustment and then double and triple check your measurements as you move things around. Recheck pinion angle, how square the rear end is in the car, and how centered the rear end is after each small adjustment. If you are really tedious with your measurements you will be able to plot out what each adjustment does.

Also, alot of people do not realize that when you attempt to crank some preload into one of the upper control arms that you really are not doing much. I have seen this first hand with a car sitting on a set of corner scales. On a car with no ARB the guy shortened the passenger side upper link a full turn from neutral and the weight bias on the rear tires changed a whopping 15 pounds. Now if you were to do this in a car with a parallel 4-link with a centering device (diagonal link, panhard bar or wishbone) you would find that a full turn on any of the control arms makes a HUGE different in the weight bias!

This is all stuff that I have picked up hanging around and learning from the TRZ guys. I am just glad that they have not run me off with all of the dumb questions that I have asked them!

 

[James Bond]

thanks for the info. i think i'm going to come up with some expectations of what the adjustments should do and then compare it to what it actually does. i'd really like to come up with a combo of turns for each arm that moves the rear one way or the other with no other effect. we'll see if its possible.

 

[gman415]

Sorry for not responding, but I was out of the loop over Christmas. Those were some good post from CutlassRacer. Just try and picture it in your head. The top right for example, is at a angle. If you make it longer the axle is moving to the right and back. But the lower right bar is going to keep it from moving back much just the "roll" around the mounting point.
On a four link the length you add is going strait back.