Allignment Question
 

I'm hoping someone can provide some perspective for my 1980 911 SC.

I had new tires mounted in the rear last week and got an allignment. My car handled fine before the allignment and tires. It tracked well on center and was very linear and predictable on turn in and rotation. Right rear tire wear was slightly accelerated compared to left rear. Fronts tire wear is balanced. After the rear tires were mounted and the allignment was changed, I noticed a significant change - not good.

On center, the car hunts. Every road surface imperfection cause the car to move left and right - requiring a minor correction with the wheel. It doesn't feel stable. Turn in is instantaneous and exagerated. As soon as the steering wheel is turned, the car darts that direction and the back rotates a LOT harder than it did in the past. Instead of a progressive rotation, I can feel the tires and suspension load up instantly and the car becomes a lot more sensitive to throttle steer. I noticed that with a full tank of gas, the problem is less pronounced than with an empty tank.

Here are some details to work with:
Stock setup with 190K miles
Front strut bar
Turbo Tie Rods
Closer to Euro than US ride height
Front tires are Toyo Proxis 4 with good tread depth @ 30 lbs
Rear tires are new Toyo Proxix 4 with 34 lbs
Front Left Caster went from 6.4 to 6.6
Front Right Caster went from 6.4 to 6.8
Front Left Camber went from -0.7 to -0.8
Front Right Camber went from -0.5 to -0.6
Front Left Toe went from -0.10 to 0.15 (big change)
Front Right Toe went from 0.10 to 0.15
Rear Left Camber is unadjustable at -0.07
Rear Right Camber is unadjustable at -1.4 (must be that curb that launched over)
Rear Left toe was unchanged at 0.20
Rear Right toe was unchanged at -0.05

Is there a better allignment option? Is there something else to consider?

New tires in back, and not new tires in front is likely the problem.

The rear tires will need to be scrubbed in and heat cycled before they stabilize. With the front tires already worn-in, what you end up with is the tail wagging the dog.

Unadjustable rear? Why?

It sounds like you need a new alignment guy. Call Darin at West End Alignment (310) 808-9233. Best in the biz...

Bingo. I read your results as having toe out both front and rear? Mismatched rear camber and mismatched caster?

Wow.

It couldn't be much worse. :)

Air cooled 911's have many more adjustments and are significantly more difficult to adjust than say, a modern BMW. Comparitively they are a big PITA and the average alignment guy just won't bother.

Take the car to a dedicated early 911 specialist and pay for several hours of labor. It'll be much better.

Please keep your threads together :)

http://forums.pelicanparts.com/porsche-911-technical-forum/484584-allignment-question.html