Tires
Alignment Procedure
#1
THE HUNTER MACHINE IS VERY ACURATE! The problem is the at the operators and the shops have no clue how to align a performance car with gas shocks. Here is the problem:
1. you drive the car in , the suspension is settled, and then they put the car on the rack and cannot check the alignment unless they calabrate the radio transmitter run out devices that clamp on the wheel.
2. They raise the car and spin the wheel to set the sensors , and then lower the car THIS IS THE PROBLEM. MY CAR WAS 2" HIGHER THAN WHEN I BROUGHT IT IN.
3. Now they set the cars toe. 0 degress or .25 degrees is fine. but as the car settles, it toes out. Now you are looking at 2.5 degrees of toe out.
4. The only way to align a 928 , is to mount the sensors on the wheels and insead of lifting the car, ROLL THE CAR BACK OFF THE RACK SLOWLY TO CALABRATE THE HUNTER MACHINE. Then roll the car back on to the rack and do the adjustments. THIS IS THE ONLY WAY TO ACURATELY TOE IN THE CAR AT THE TIRE STORE. DO NOT LIFT THE CAR. I've had my car for 14 years and had some of the best alignment guys screw it up. The only time it was done right and didn't wear the heck of the tires was to do this technique.
5. DEVEK has a lot of luck doing it manually. I've tested mine manually in my garge with lazer pointers on the rims (front and back of the rim pointing to the ground.) measure the distance between the dots from the rear of the rim on both sides compared with the front dots.
6. As far as the settings from the factory, .25 degrees or (15 min ) is the spec for total toe in. 0 is fine but 30 min or 1/2 degree is a little on the high side. Diff between the wheels is not that critical, but the hunter is the ideal choice for a very acurate set up.
7. Dont let the operator say it can't be done. Just say, "how much difference in suspension geometry does it make to have the car two inches higher?" If he can't answer or says "a lot" then he will comply. The setting for the hunter sensors only requires to rotate the tires 270 degrees to set the runout, which means about 15 feet backing up off the rack with everything attached.
8. If these guys have every got an alignment right, it has been luck. I have, many times, wished my alignment to be right as I chewed up 400 bucks worth of front rubber.
#2
I had my 87 S4 aligned at "RPM" in Virginia Beach, VA. The area code there is (757). The lead mechanic there is named Francis and he is a 928 expert. He owns 2 right now and I think has had a few in the past. He is also a very nice guy that has given me alot of free advice. He did an alignment on my car. He did have to jack down the front suspension and said this always needs to be done to align a 928. The car came out great. It pulled to the right and wore tires to the inside before the alignment and both problems were cured after. Give him a call and just explain your situation I'm sure he'd be able to tell you what you want to know. I don't remember their phone number but like I said its in Virginia Beach area code 757; you could call information or look it up on the web. For anyone in the area, I highly recommend this shop.
#3
Absolutely (#2 above), although Mark Kibort just posted a clever way to avoid it (which amounts to avoiding jacking up the front of the car). Everyone open your shop manual to page 44-2, where Porsche points out that the "Actual vehicle height...is lost if the vehicle or front axle have been raised." and goes on (page 44-3) to show the official "pulling down procedure" which uses "special tool 10-222A" to pull down the car's front end by 60-70 mm (almost three inches) and hold it there for one minute. Page 44-2 warns that aligning the front end after it has been raised will give incorrect toe-in. This has nothing to do with the alignment rig, just with the design of the 928 front suspension, which needs to be driven for a while or pulled down as above in order to recover its standard operating height after being jacked up.
#4
The settling of the suspension really only affects FRONT TOE - minimal effect on camber, caster, and rear wheels. If you want to jack the car up to set all the others, fine, but then come back a few days later and set the toe without jacking - there is no reason at all to jack up the car to set the front wheel toe!!!
#5
Remember, Hunter machine!
1. dont jack the car up, just roll back with the calabraters attached to the wheels, the 270 degrees necessary to calabrate the machine
2. roll (drive the car back on to the rack) the calabrator are radio transmitters, no wires.
3 . do aligment. I suggest 0 toe, .75 to 1 degree of negative camber. (more for agressive driving less for just hyway) Rears to spec, but more negative camber for handling
*MK
#6
The front suspension geometry of all 928s is such that as the weight on it is removed, it experiences major positive camber and some toe-out as well. Each lower control arm has a large (unlubricated) rubber bushing on each end. These do take a "set" and will not move back if the car is just lowered. Also, as the car is lowered, the outer treads of the tires grab first, and impede movement outward. Lowering the car onto plates that slide right to left helps, but does not do anything for the "set" taken by the bushings. I read a posting that said to loosen the lower control arm so the bushings could more easily "re-set." Personally, I'd be reluctant to do that, since each control arm is supporting about 850 pounds or more.
So then, how does one do a proper alignment on a 928? The way I think works best is to drive the car part way up the alignment ramp five feet short of the final resting pad, install the laser measuring devices, then drive it the rest of the way up (which should cause the devices to experience 270 degrees of rotation). DO NOT LIFT the front of the car. (The rears are not as critical.) YMMV.