UKKid35

I've replaced the front shocks and ride height adjusters and set them to their maximum (so none of the sleeve is visible), front is still about 1/2" lower than the rear but just within spec.

I've adjusted wheel bearings and driven the car across bumpy London (more than enough to settle the suspension).

When I get to the only alignment shop regularly recommended by 928 owners they tell me that the rear camber adjustment bolts have been fitted back to front (bolt head towards the rear of the car).

Even so they do a very good job of getting measurements within spec. The left castor they said is now at the maximum adjustment. The first sheet is the before, and second after. Cost of alignment about $300, the problem is that the car still pulls to the left.

I'm going to swap the badly worn tyres very shortly with a pair of relatively new evenly worn ones, but I'm not convinced this will cure the pull to the left.

What do I do now?

drnick

paul i hear you! my 86 had me exasperated with no confidance inspiring handling for ages. despite your suspicion that the alignement is still incorrect you need to replace the badly worn tyres, then get it aligned again. i wouldnt be surprised if both the front and rear toe are both still out. have the castor set to its maximum on both sides at the front and i think you can run with even less front toe than currently. make sure the car has a full tank of gas too.

the camber settings are very conservative and you can easily run these on the higher side of the normal range or over without increasing tyre wear unduely. ive had so many alignements done over the last 2 years its not funny, each one has occured after something or other was changed out on the suspension. ive had good alignements achieved at kwikfit as well but you need to pick your shops...

Earl Gillstrom

Paul,

Your alignment shop does NOT have the correct 928 numbers in the computer. I have never seen one that did. Go to my site for the correct (Porsche recommended) numbers. http://members.rennlist.com/captearlg/ Check out the complete alignment section, including miscellanious ramblings.

It seems like one alignment equipment manufacturer used the wrong numbers and all other manufacturers copied them.

For street cars I do NOT recommend changing from Porsche alignment specifications.

Your left caster is within spec. The right should be adjusted to the same caster as the left. This may correct the pulling, but I doubt it very much. Your cross caster is within Porsche specification.

The number one reason for a car pulling is bad tires. NOT alignment. New correctly made tires will probably correct your pulling problem.

If new tires correct the problem, then your alignment is OK and no reason to do another alignment.

jserio

The tire condition is very important. I would never get an alignment on tires less then 85% and even that is stretching it. Case in point, I had brand new tires on my S4 when the alignment was done. The alignment is/was spot on. Then I sold those wheels and put on wheels with fairly new tires but worn a little bit that were on a car with a bad wheel alignment. Now my car pulls slightly now. Not much but it is noticable. That is the only logical explanation.

jpitman2

Captn Earl, My last alignment sheet shows ranges that agree with your figures (except my toe is shown in mm not degrees - total front 1.8 (spec 1.8 +/- .6), rear 1.0(spec 1.2+/-.6)). I cant read all of Paul's specs clearly enough, but those I can, match my specs - rear camber 40mins+/-10 = 30-50mins. Seems to me the only error is in the change of caster from 86.5 up.
jp 83 Euro S AT 48k.

drnick

i bet that if you put on alignement gear with new tyres the front and rear toe will be different/out.

WallyP

I can't think of any reason that the alignment should change when you change the tires. The way the car drives will change, but I can't see the new tires bending steel to change the alignment...

Earl Gillstrom

The only criteria I have for aligning with worn tires is that they are worn to about the same diameter on each axle. In other words: If you have a bald tire on one wheel and a new tire on the other wheel on the same axle, the car is not level and the alignment would be incorrect. I have never tried this, so don't know how far off it would be. It would be like aligning with air pressure not correct on one tire.

JP, Yes, the main problem with alignment specs is the difference between '86 and '86.5 and later. I have also seen incorrect toe-in specs. Toe-in specs in MM or inches is the old way and not used much any more since computerized alignment was introduced. Using the formulas on my site, you should be able to convert back and forth between the two measurements systems.

Paul, Also note that if your front and rear heights were correct, your front caster would be closer to the maximum of 5 degrees. That is very typical of most of the 928s that I have aligned (28 and counting). I normally turn both casters to minimum and then the one with the least caster up to match the other. As long as there is no cross caster, 928s are not very sensitive to actual caster. I cranked one up to 8 degrees and the steering only seemed slightly more sensitive. I am sure that it was harder to steer, but I couldn't feel it. Power steering seems to cancel it.

Tommy928

Paul,

The caster spec for the 87' S4 is 3 degree 30 minute + 30 minute max or 4 degree. The max left to right difference is 20 minute. Since you have an 8 degree left to right difference I doubt that you will resolve your pull problem just by a change of tires. I would definitely fix this problem before I would replace the tires. Tommy

Earl Gillstrom

Tommy928,

The caster spec for the '87 WAS 3.5+.5 or max 4 degrees. About 1990 Porsche realized that this was impossible on most cars and changed the spec to 4 +1" retrospectively" back to '86.5. My shop manual page 44-05 is dated 1993. After aligning 25+ '87 or later cars, I have never been able to get one below 4 degrees caster. Most are ~4.5 degrees.

8 degrees left to right difference?? I read it as 19 minutes difference. This is within Porsche tolarance but only 1 minute within. I doubt that this would cause the pull and think the tires are the problem. Although I normally adjust with no tolarance.

See my website for all you ever wanted to know about 928 alignment, and how to do it yourself. http://members.rennlist.com/captearlg/

Steve J.

Tires shouldn't effect the alignment (except maybe different diameters on each side). You are aligning the wheels, not the tires.

jpitman2

My caster came up at 3d48m left, 3d50m right....
jp 83 Euro S AT 48k

Tommy928

Earl,

I miss read the left castor (in red) as negative 4 degree and that's how I came up with 8 degree difference. Yes, 19 minute should not cause a pull problem on stock size tires/wheels.

At around 1991 Porsche increase the castor to 5 degree max. I thought it was done to increased straight line stability because the power steering pump was turned up to increase assist and the higher castor would help maintain steering feel. By the way I had no problem adjusting the castor to 4 degree on my 87' S4.

UKKid35

Thanks to everyone for their thoughts, especially Earl, who's alignment site I have printed out and read more than once in the past. I'd really hoped you would chip in on this thread.

The reason I've been running on badly worn tyres is that my suspension has been so badly out that it eats tyres very quickly, the upper chart is actually after doing some crude changes myself, although not before completely destroying one pair of tyres. I recently treated myself to a second set of wheels and have put some good used ContiSports on them. I swapped the fronts last night and will find out shortly whether the pull has gone when I drive down to a small 928 meet in Kent where I will meet John Eifert for the first time. His site detailing clutch change has been a great help and I'm glad I'll get to thank him in person now.

UKKid35

With fresh tyres the stability is much improved, but there is still a slight pull to the left, much more noticable under heavy braking. This is not going to spoil my enjoyment of the car, but it's not ideal. I'm going to double check ride height to ensure that it's level side to side, but I've no idea how to find someone who can check the corner balancing. I'll probably get the alignment re-checked, afterall I've gone this far. Anything else worth considering?