: Alignment Issues



ssmith100
07-09-05, 12:37 AM
As some of you know I have put a very large tire on the rear of my car now and am seeing an alignment issue. Our rear ends are set up with about 1.5 degrees of negatve camber from the factory. After installing the 295's on the back it has really exagurated that much camber to the effect of the last 1/2" on the outside of the tire not touching the ground. The car is going in Monday to have the camber adjusted to compensate for the tires. Anybody have any idea how much if any positive camber i should bring in to compensate?? Posting a pic that you guys can hopefully see what I'm talking about.

By the way, that 60mph shake I had in the steering wheel is now gone by adjusting the toe on the front end. No more steering wheel shake.

Shane

Dave's V
07-09-05, 12:40 AM
It seems like the outside part of the tires wears out faster with stock tires. Have you had your alignment checked? I wouldn't be surprised if it was screwed up.

ssmith100
07-09-05, 12:49 AM
The way my car is sitting with the negatve 1.5 degrees of camber, they are going to wear on the "inside" very bad. Going to try and add some positive camber to pull the bottom of the wheel in some more. I had it on a Hunter machine today and checked the specs.


Shane

Dave's V
07-09-05, 01:18 AM
Shane,
Oops! I got my sides confused.

Dave

Dreamin
07-09-05, 01:40 AM
Shane the spec for the rear is... Camber Range: -1.0 to -1.8 / Optimal: -1.4 (FE3 spec, no FE4 specs).

So -1.5 deg should not destroy the inside edge... that's the factory spec, the suspension is setup for this. And the outside 1/2" not touching the ground is more tire size and wheels, than the -1.5 deg.

But you can definitely run less camber with larger and taller wheels, without it affecting handling.

HMO:
For the increased width, reduce 0.3 to 0.5 deg.
For the increased height, reduce 0.2 deg

So run -0.8 to -1.0 camber.
I would not run less than -0.5 camber...

This will also reduce understeer (caused by the staggered setup)

A "discussion" I had with globed70 about high camber setting... i *think* i won the arguement: http://www.cadillacforums.com/forums/showthread.php?t=19570

Dreamin
07-09-05, 01:48 AM
Not the best picture, but my 275's on the stock 8.5" also lifted on the outside edge.

The 275s are wide for the 8.5" wheel. And 295s are also wide for a 10" wheel (within spec, but the smallest wheel you can run w/295s). This is causing the lift. Not a big deal, does not mean the inside will wear out faster... that's a function of camber. FWIW, the CTS-VR runs 275's on 11" wheels.

http://zeemr.home.comcast.net/275-3.jpg

Dreamin
07-09-05, 01:51 AM
By the way, that 60mph shake I had in the steering wheel is now gone by adjusting the toe on the front end. No more steering wheel shake.

Please post your before's and after's.
Thx.

greggbruce
07-09-05, 02:08 AM
camber DOES cause inside or outside tire wear.

the ideal setting is 0.
zero.
but you also have to keep in mind in a turn, it changes.
what do you do more??
turn or go straight?
it's good to have some negative camber on the rear for increased handling, but going too much just wears the tires and is a waste.
my corvette runs 3 degrees negative(it's a road-race car), but my old fleetwood d'elegance I ran .2 positive, cuz when I put stuff in the trunk (trip to the lake) or people in the back seat, it went just slightly negative. I think I aligned it with a couple hundred pounds in the trunk and set it to dead nuts zero.
If you go to a fatter tire, it will be more sensitive to the camber setting, so, it's kinda' tial and error, get a tire depth gague and check it often to see if inside or outside is wearing more and make camber adjustments accordingly.....

just my 2 cents..