Wheel Alignment

Marc:
The sequence for wheel alignment of a 928 should be:
1)  Check and adjust tire pressure.
2)  Check ride height
3)  Jack up and check for and replace worn/damaged parts.
4)  Adjust ride height.
5)  Drive 25 to 100 miles over bumpy roads.*
6)  Repeat 1,2. If jacking is necessary, repeat 5 and start over. DO NOT raise car before or during alignment
7)  Adjust camber and toe in on rear wheels
8)  Adjust camber and caster on front wheels.
9)  Install rack centering bolt.
10) Adjust front toe in.
11) Check for level steering wheel and pull and adjust on splines if necessary.
12) Remove rack centering bolt and replace with plastic plug.

Specifications:          
 

The shop manual has complete procedures. This document is meant for sequence of adjustments and quick reference of specifications.

* I have found that 5 miles driving is not adequate to settle after jacking. The 25 to 100 mile figure may be reduced by sitting time. YMMV

Earl Gillstrom '88 S4 5 Speed
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PJ, here is a listing of the correct ranges:
   

 
These specs were on the print out from my SUPERB alignment from Butler Tire in Atlanta.
I am assuming that they are correct, because the tires are wearing correctly, (not on the inside edges) and the car tracks and handles beautifully. I briefly looked at your alignment numbers, and it looked like a few were slightly out of tolerance. Hope this helps out.

Chris L.
'89 GT  ( that drives straight and true)

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Here are my alignment figures (post-alignment, that is).
Can anybody tell me if I'm within or close to spec?  These look a little fishy.

FRONT
CASTOR              +3.48       +3.48
CAMBER              -0.68       -0.80
TOE                      +0.11       +0.08
TOTAL TOE         +.019

SETBACK           N/M
SAI                      N/M
INCL ANGLE      N/M

REAR
CAMBER          -1.04       -0.76
TOE                   +0.17       +0.17
TOTAL TOE     +0.34

THRUST ANGLE    0.00


Thanks in advance, PJ
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I think I did this before, but..
1.  Find as level a surface as possible side-to-side to park the car.  If you can't find a place level you have to make camber measurements with the car facing both ways and take the average reading.  My garage floor happens to be very level - I checked by running water on it to see if it runs one way or the other.

2.  Calculate the required camber and toe-in specifications in inches.  My car has 16 inch wheels and it is very close to 16 inches between spots on the rim where I can take a good measurement.  For 30 minutes +/- 10 minutes camber it figures out to 3/32 to 3/16 inches difference in 16 inches.  For toe-in the distance between the front of the tire and the rear at the level a tape can be stretched across is about 20 inches.  In this distance the required difference is 1/16 to 1/8.

3.  Camber must be adjusted first as it effects the toe-in.  I use a carpenter's level - you need one at least 2 feet long.  I put the level against or near the bottom of the tire and measure in to the wheel at the top and bottom of the rim - not at the lip, but on the flat part.  The difference is the camber.  Adjust the cam until it's right.  After you think it's right roll the car back and forth to get rid of any distortion left in the system.

4.  For toe-in it takes two people to measure between the same tread elements at the front of the tire and the rear, being careful not to bend the tape under chassis elements.  Tires are not necessarily straight, so it takes more than one measurement to have confidence.  Either tie rod can be adjusted.

5.  After the toe-in is correct the rack and steering wheel need to be centered.  Take out the plastic plug in the front of the rack and either use the tool sold or I just sight in the hole and turn the steering wheel until the depression in the rack is centered in the hole.  Now might be the time to remove the steering wheel if necessary to install it in the "straight ahead" position.
Don't compromise on the centering of the rack to have the steering wheels straight - the rack is made with the center teeth a little tighter than the others to eliminate play in the straight ahead position.  I used a long straight-edge and sighted along the outside of the tire to the rear tires. Then adjust both tie-rods and equal and opposite amount until the outer edge of both front tires point to the same part of the rear tires.

6.  Now drive the car a little and check it again and adjust as necessary.

I found that after I followed the above procedure the car tracked straight with the wheel centered. One confession is the castor angle, which I haven't figured out how to adjust accurately.  I just set the cam in about the center of its travel and left it.  The wheel centers nicely from a turn in either direction and there is about the right amount of steering effort when cornering hard.  I might just leave it the way it is.

sorry about the long post.
Gary Casey

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Ed,

Kind of but not really. Those ball joint attachments are in line with the inside of the rim so that puts them about 1/2 of a tire width from the application of the load. If you have a 225 on the front that would be about 4.5" inboard of the center of the "contact patch" (sorry). And that is about 25-30% of the distance from the attachment to the body my guess. And, by lifting that way you take a chance of preloading the lower arm bushings so  that would throw you way out. So you are right that it is better but it isn't true that it maintains equilibrium.

I have measured my alignment settings over a month after a complete lift. It keeps changing. Also, if you don't settle the car completely before measuring you can be off a bunch. Just driving the car up to the rack and getting out can leave it off it's correct height by quite a bit. And if that is the case the alignment will be off. In your case that means that you will probably toed in after a week or so more than spec. But you probably don't go back and have it checked so you don't know and it probably isn't enough to wear tires within a medium rotating time spans.

The ONLY way to properly align a car is to measure the height of a settled car before starting any changes and making sure it is still the same after the changes. If you want to prove this is true put a laser on a wheel, any wheel and point it at a wall 6 feet away. Then jack that corner and watch the lateral movement of the laser. It is dramatic. Lift a little, move a lot. Then point it at the ceiling and do the same. Watch the lateral movement when you lift. Those two things are showing you bump steer variables btw.

I would bet a beer at SITM that I can lift your GT by the ball joints and set it back down and the height will be off. And if you have upgrade springs and gas shocks I bet I can do it to the rear too. I will bring the laser and the camber gauge just for fun... :) Worst case you or I or both get a beer that I buy. Sort of a lose/win or win/lose.

Moral: don't lift the car. It isn't necessary. If you are going to a tech that says so. Run away!!!!!!!

Jay Kempf

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Graham,

I have found quite a few late 928s that have rear camber out of tolerance. The spec is 5/8 degree negative and most are closer to 1 degree negative. Usually the left is worse than the right. It seems that they can be up to 1 1/4 negative (street cars) and not affect tire wear or steering feel or handling. Just mal adjust the right to match the left. The racers like even more negative camber.
I have fixed a few by putting a worm drive hose clamp (Jubalie clip) on the camber eccentric. This increases the diameter of the eccentric enough to allow proper (or close) adjustment. You will have to jack the car up to install the clamp. If you jack only the rear, the car will settle in a few miles.

Toe in is the most critical adjustment as far as feel and tire wear.
When toe is too much or too little one tire steers the car and the other drags sideways. Then you hit a bump and the other tire takes over steering and the car feels very unstable.

Take a look at my website on home alignment for more info.
http://members.rennlist.com/captearlg/

Earl Gillstrom

The Camber seems wrong....