handling question

[73RSZ28]

Since I installed the new tires and wheels, the car wants to dart around on the highway. Do I have an alignment issue or what?

Tires are Kumho Ecsta MX 200 UTQG.

Fronts: 245/45/17
Rears: 275/40/18

[MrQuick]

Yep, start with the alignment and go from there. Be sure to make note of the old specs. We would like to see them.

[73RSZ28]

I had it aligned but I think they put it to stock specs.
Left Right
Camber 1 1
Caster .4 .2
Toe .2 .2


What should I be running?

[SLO_Z28]

What should I be running?

Toe in. It sounds like that is .2 toe out. Toe out will pre load the tire for turn in, which is good for racing but makes the car follow every little variation in the road. Toe in will load the tire in the opposite direction and make the car track better. Additional positive caster will help the car feel more stable too.

[73RSZ28]

it is toe in. total toe in is .36. I think it could use more positive caster.

[TheJDMan]

I had it aligned but I think they put it to stock specs.

I had a similar experience with a local alignment shop. Mind you I have a DSE subframe front and G-link/9" rear. The tech asked what year it was and started looking up specs for a 68 Camaro. When I informed him that he couldn't use the factory settings he said that was the only way he could set the front end. Needless to say I left at that point. It was interesting to learn that some repair shops have policies that require the tech to only use factory specs completely ignoring non-stock suspensions. I finally just decided to buy the tools and do my own alignments.

[sgernon]

Not to hijack the thread but JDMan how easy and accurate is it to do your own alignments? How long does it take and which tool do you have?

[SLO_Z28]

Not to hijack the thread but JDMan how easy and accurate is it to do your own alignments? How long does it take and which tool do you have?

It can be very accurate. I do my own alignments. If it was my car I would keep the steering wheel centered and turn the tie rod adjusters half a turn each side for more toe in and test drive it.

[73RSZ28]

It does pull to the right also.

[SLO_Z28]

It does pull to the right also.

The cross caster (difference from right to left) is causing that.

[73RSZ28]

Where do you shim for positive caster?

[Twentyover]

Same place as camber, upper A-arm bolts, but use different thickness shims front and rear

[73RSZ28]

Same place as camber, upper A-arm bolts, but use different thickness shims front and rear

I got a handle on that much, what I'm asking is where to put more shims front or rear?

[SLO_Z28]

Putting more shims in the upper control arm on the rear (near the firewall) bolt will increase the caster. It moves the upper ball joint further towards the rear of the car, it will also move the ball joint toward the center of the vehicle slightly and increase the camber. I would say 1 1/8th inch shim to both rear tires and a 1/4 turn of toe in, and your pull will go away.

[keithq69]

More shims on the rear bolt will tip the ball joint back and give you more caster.
You need to do it in the right order so you don't mess up either caster or camber when you set the other. Not sure what the order is.

[SLO_Z28]

Well to adjust caster and not change camber you need to take a shim out from the front. The amount of shims to add and remove is a simple trigonometry equation, most good alignment racks will not only let you input your desired end stats, but also calculate how many shims to put in. The the home customer trial and error is usually easier and faster.

[73RSZ28]

Well I took it back to the "big box store" that did the alignment the first time. I requested the specs to be set at 2-3 degrees positive caster, 0-1 negative camber, and 0-1/16" toe in. They would not deviate from the factory specs and kindly gave me a refund. I located a local shop owned by a SCCA guy and he was more than helpful. We ended up at 1.4 degrees positive caster, 0 camber, and 3/32" total toe. He ran out of adjustment on my studs. Also my drivers tire is starting to rub the bottom rear of the inner fender.

[SLO_Z28]

Drive better now? Thats what really matters.

[73RSZ28]

Seems to be more stable, time will tell. Some aftermarket control arms are in my future!