Early Car wandering at speed

[daepp]

I have recently had a 4 wheel alignment and added two new front tires simutaneously. The car previously tracked well on freeways at 80mph, but now it seems to need many more "corrections" to keep it where I want it. The reason I took it in for an alignment was that the right rear tire bottom was visibly cambered in and wearing off the outside edge of new tires.

The independent, well regarded Porsche-only wrench found many problems with the previous alignment - front and rear - and said he corrected them all.

The new tire set-up is:

Front - 205-55-15 - new
Rear - 205-60 -15 - old

I was hoping to get a little more wear out of the rears before replacing them for 205-55's, but now I'm wondering if this set-up could be contributing to the "wandering" effect.

Any ideas?

[john walker's workshop]

take it to another alignment place. 15" tires really don't have very stiff sidewalls, so that contributes to the problem. push the car sideways by hand and watch the bottom of the tires move.

[daepp]

Do you really think the alignment is wrong? This guy is well respected both at the track and for street.

[john walker's workshop]

i use only one alignment shop here in seattle. i've been through several over the years that supposedly were "experts", and the cars handled like crap and wore out tires. wouldn't hurt to double check the job elsewhere, at an equally respected shop. either that's or ask the original guy to investigate your issue. maybe it needs a bit more toe-in or some other minor tweek. you went with shorter sidewall front tires, which generally means that they are a bit stiffer than the old, taller 60 series tires, but left the 60s on rear. so now the front end has a tad more stability than the rear end, so the tire swap might contribute to the problem too.

[daepp]

All good advice - thank you.

I was wondering if my tire set-up could be causing the problem.

[gsmith4965]

Sounds like either a toe out issue in the rear or too little castor in the front.

[widgeon13]

Check to see if the front and rear tires are the same speed rating, if they are not, they need to be. V, W, Z whatever, they should all be the same speed rating. That will definitely make for a challenge as far as directional control.

[Adam Reed]

A couple more things. First. check your tire pressures. If they are very high, the handling can be scary indeed. I just got 2 new tires to make 195-60-15 all around on my new 6 inch Fuchs. Took it out for a drive and scared the s**t out of myself at 80-90 MPH on our amazing Southern Oregon back roads. I found that the gorillas at Les Schwab (Oregon tire dealer) had helpfully jacked all 4 tires up to around 40 PSI. Took them down to 32 all around (this is a 912, so good weight balance) and it's stable as a rock. Seems counter-intuitive, but there you are.

Second, make SURE the alignment guy got the toe-in correct on the rears. This makes a huge difference and as we all know, it's a pain to get right.

cheers
Adam912.Out.
'66 912, 485K mies, 2.2L of lightweight T4 fun!

[tfiv]

Are you running a different brand, model tire front to rear?

[daepp]

Front and rear are Yokohama AVS. Same everything but size.

[BURN-BROS]

A toe'd out set-up would cause a bit of wandering. Just have the place you had it aligned tell you what they set toe at(for reference). The car should be toed in slightly to account for a bit slack that the car takes up when it up to speed.

[daepp]

Here are the before and after settings per work order:

Before Rear: (-) 1.6 neg. camber on left, (+) .9 pos. camber on right. Total Toe was 1/2".
Before Front: (-) 0.6 neg. camber on left, (-) 0.3 neg. camber on right. Total Toe was 1/4".

After Rear: (-) 0.1 neg. camber on left and right. Total Toe = 1/8".
After Front: (-) 0.4 neg. camber on left and right. Total Toe = 1/16".

Does any of this sound right?

[daepp]

BTW, he did say that the set-up was way off and had many loose botls when he started the work.

[BURN-BROS]

Have him bring front toe to 1/8" and see how you like it.

[john walker's workshop]

yup, more toe.

[EarlyPorsche]

Toe it is. Directly related to wandering.

[daepp]

Thanks guys -a ll of you! Taking back tot he wrench Monday. Do his settings make sense in any application - say for track? He certainly seemed real precise and quoted factory specs.

[cmcfaul]

My car used to wander, especially at higher speeds. Worn rear bushings were the culprit

Chris
73 911 e

[Richard Burns]

Are the new tires directional and on the right way 'round?
I know your car wasn't wandering before the alignment but if you have a whale tail and no front spoiler your car will wander at speed.
Good luck on Monday.

[daepp]

Tires are unidirectional and installed correctly. No whale tail, but didn't wander before.