Alignments and tire wear.
12-11-2002, 03:19 PM
#1
Nordschleife Master
Thread Starter
Alignments and tire wear.
I had a shop align my US 83 928S.
I "know" they screwed it up, but I can't prove it. If anything I've ever read on the net about aligning 928s is correct, he screwed it up. However, I'm not the tech, and the tech that did it was suppost to be fimiler with the 928. Was refered by a European Car shop. the tech had been in the bussness for 20 something years, and started out on a string machine. He now uses a Hunter.
My question is how many miles does it take before you start to show uneven tire wear? I just bought a tire tread measureing thingie. The tread depth is the same, accrost the tire. I've put about a 1000 miles on them already.
When should I expect to see any diffrence?
I "know" they screwed it up, but I can't prove it. If anything I've ever read on the net about aligning 928s is correct, he screwed it up. However, I'm not the tech, and the tech that did it was suppost to be fimiler with the 928. Was refered by a European Car shop. the tech had been in the bussness for 20 something years, and started out on a string machine. He now uses a Hunter.
My question is how many miles does it take before you start to show uneven tire wear? I just bought a tire tread measureing thingie. The tread depth is the same, accrost the tire. I've put about a 1000 miles on them already.
When should I expect to see any diffrence?
12-11-2002, 03:32 PM
#2
Range Master
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If the "screw up" is that he raised the car off it's suspension, the wear on the inside shoulders may begin manifesting itself in a few thousand miles. I had a set of tires RUINED in about 5000 miles, because I didn't take a look at the inside shoulders. The rest of the tire was fine but the inside shoulders were worn to the chords.
12-11-2002, 04:12 PM
#3
Burning Brakes
A good way to tell if the tires are going to wear prematurely is to check the front alignment toe. If it's more than 1 degree out, the tires are going to wear sooner than later, all other things being equal (which they never are). 
Checking front toe is not that hard to do. I do it on a perfectly flat floor, a plumb-bob, a 4' level, and a tape measure that is at least 7' long. YMMV.
Checking front toe is not that hard to do. I do it on a perfectly flat floor, a plumb-bob, a 4' level, and a tape measure that is at least 7' long. YMMV.
12-11-2002, 08:49 PM
#4
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Vibrusunits,
If you have put on 1000 miles since alignment and the tires are wearing even across the tread, then the toe in is probably OK. How do you "know" that the alignment is not right?
Here are several quick checks of toe in.
TOE-IN-- Get down behind the car and eyeball the outer edge of the tires through the axle center from back to front. You should not be able to see the sidewall in the front of the front tire if there is some toe-in. Check the other side of the car. The rear can be checked the same way.
If you just had the car aligned, and the toe-in looks OK, then check again in 100 miles. If you can now see the front side walls, then the car was probably aligned without settling first and may destroy the front tires in less than 1,000 miles.
A slightly more accurate check can be made using string. Using a string on each side of the car and several feet longer than the car, at axle height, make them parallel. Jack stands work good for holding the strings. Measure in from the string to the tire bead on the rim. The front of the rim should be ~ 1/32" further in than the back of the rim for front wheels and 3/64" for rear wheels.
If you did not drive the car into the measuring spot with the wheels straight ahead, you may have to average the sides or drive the car in again. Without slip plates, you can't just move the wheels.
If you have put on 1000 miles since alignment and the tires are wearing even across the tread, then the toe in is probably OK. How do you "know" that the alignment is not right?
Here are several quick checks of toe in.
TOE-IN-- Get down behind the car and eyeball the outer edge of the tires through the axle center from back to front. You should not be able to see the sidewall in the front of the front tire if there is some toe-in. Check the other side of the car. The rear can be checked the same way.
If you just had the car aligned, and the toe-in looks OK, then check again in 100 miles. If you can now see the front side walls, then the car was probably aligned without settling first and may destroy the front tires in less than 1,000 miles.
A slightly more accurate check can be made using string. Using a string on each side of the car and several feet longer than the car, at axle height, make them parallel. Jack stands work good for holding the strings. Measure in from the string to the tire bead on the rim. The front of the rim should be ~ 1/32" further in than the back of the rim for front wheels and 3/64" for rear wheels.
If you did not drive the car into the measuring spot with the wheels straight ahead, you may have to average the sides or drive the car in again. Without slip plates, you can't just move the wheels.
12-11-2002, 09:56 PM
#5
Nordschleife Master
Thread Starter
The reason I "know" it was screwed up was it was picked up.
The tech said it was OK, but well, after all the stuff I've read about that, thats deffently bad.
The tech said it was OK because slip plates on ball bearings would let the car fall back to ride height. I don't have any information about this, so I gave him the benifit of the dought. The plate was on bearing so that it would slide outward when the car set on it. The tech talked like he was realy impressed with it. Like it fixed the 928's unusual tendancys at the alignment rack. Does this change anything?
I'd did a check, and I've got over 1,000 miles (clost to 2,000) on em, and I can't tell any diffrence accrost the tread. Well, nothing more than maybe an estimated 1/4 mm. But every time I check, it's never constant. The tire tread measureing thingie is only graduated to the mm, and I can estimate to about 1/2 w/o too much difficulty. Always about a quater mm over 7mm depth on the outside tread.
The tech said it was OK, but well, after all the stuff I've read about that, thats deffently bad.
The tech said it was OK because slip plates on ball bearings would let the car fall back to ride height. I don't have any information about this, so I gave him the benifit of the dought. The plate was on bearing so that it would slide outward when the car set on it. The tech talked like he was realy impressed with it. Like it fixed the 928's unusual tendancys at the alignment rack. Does this change anything?
I'd did a check, and I've got over 1,000 miles (clost to 2,000) on em, and I can't tell any diffrence accrost the tread. Well, nothing more than maybe an estimated 1/4 mm. But every time I check, it's never constant. The tire tread measureing thingie is only graduated to the mm, and I can estimate to about 1/2 w/o too much difficulty. Always about a quater mm over 7mm depth on the outside tread.
12-12-2002, 10:06 AM
#6
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If the car was picked up, the alignment is almost certainly screwed.
Do the string test. You will probably find that the car is toed out - the wheels will point out rather than in.
If you find that they are toed out, go back to the shop, and tell the tech that you now have toe out.
Take a tape measure with you. Together with the tech, measure the distance from the floor to the fender lip. Let him jack the car on his slip plates, and bounce it all he wants. Take the car off and remeasure - it will be higher. If he is reasonable, that will convince him.
If he refuses to believe you, tell him that he is ruining your front tires, and will have to pay for a new set in a couple of months.
Do the string test. You will probably find that the car is toed out - the wheels will point out rather than in.
If you find that they are toed out, go back to the shop, and tell the tech that you now have toe out.
Take a tape measure with you. Together with the tech, measure the distance from the floor to the fender lip. Let him jack the car on his slip plates, and bounce it all he wants. Take the car off and remeasure - it will be higher. If he is reasonable, that will convince him.
If he refuses to believe you, tell him that he is ruining your front tires, and will have to pay for a new set in a couple of months.
12-12-2002, 11:31 AM
#7
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Maybe you could print out some of the previous threads on this subject if you search the archive and give them to him. Show him what a dumbass he is and if he has a shread of integrity he will redo it properly.
I have previously given a similar example where I specifically told the tech not to lift the car, so what does he do? You guessed it. He lifted the car and realized his mistake when he lowered it back down onto the "bearing plates". He said that he'd aligned dozens of 928's over the years so I told him that he'd done dozens wrong. He didn't like hearing that but was man enough to tell me to come back the next day with any info I wished him to read and he would do it properly.
You may be able to make a deal with the guy that he puts the car back on the rack without lifting it and inspects the alignment. If it's off, he redoes it free. If it's good, you pay an inspection fee for the rack time. You'll win.
I have previously given a similar example where I specifically told the tech not to lift the car, so what does he do? You guessed it. He lifted the car and realized his mistake when he lowered it back down onto the "bearing plates". He said that he'd aligned dozens of 928's over the years so I told him that he'd done dozens wrong. He didn't like hearing that but was man enough to tell me to come back the next day with any info I wished him to read and he would do it properly.
You may be able to make a deal with the guy that he puts the car back on the rack without lifting it and inspects the alignment. If it's off, he redoes it free. If it's good, you pay an inspection fee for the rack time. You'll win.
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12-12-2002, 12:39 PM
#8
Burning Brakes
This horse has been beaten before. I only want to repeat, that a 928 can be lifted in such a way that it will not affect the alignment. My tech has done it on my GT, and the alignment came out spot-on.
BTW, he's probably the exception and not the rule. He can align any Porsche with a string, a level, and a measuring tape. He's done it on many professionally driven track cars while at the track. YMMV.
BTW, he's probably the exception and not the rule. He can align any Porsche with a string, a level, and a measuring tape. He's done it on many professionally driven track cars while at the track. YMMV.
12-12-2002, 05:46 PM
#10
Burning Brakes
As stated in earlier messages on the topic, he lifts from the most outward part of the lower control arm. By doing so, the suspension either moves very little or (in the case of my GT) not at all. YMMV.
12-12-2002, 06:05 PM
#11
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This is an excerpt from the alignment presentation that I gave at the FRENZY.
I will put the complete alignment presentation with pictures on a website when I get time.
Fibunits, If your front tires are not wearing, then he probably pulled it down before doing the alignment. Do the quick check posted earlier to find out. Or take it back to the alignment shop and ask him to just check toe-in without lifting the car. Make a copy of the following to give to the aligner.
WHY 928 SUSPENSION IS DIFFERENT THAN OTHER CARS 2
The PORSCHE 928 has very unique suspension bushings compared to other cars. If you jack up a 928 and let the wheels hang down, the bushings immediately take a "set". When you lower the car back down on its tires and roll the car back and forth to "settle" the suspension, the car will now sit ~1" higher than before it was jacked up. The car will now have to be driven up to 100 miles depending on how rough the roads are to settle the car back down to its proper height. The Porsche shop manual says "after a longer journey or longer operating period".
If you align the wheels with the car sitting 1" inch higher than the normal ride height, then, after settling, the front tires may be destroyed in less than ~1000 miles due to excessive toe out.
If you align the 928 with the car sitting 1/4" inch higher than normal, then, after settling, there will be no toe-in and the tires may be destroyed in ~2500 miles.
ALIGNMENT SHOP SUGGESTIONS
Normally one of the first steps in alignment is to jack up the car and check for worn and loose parts and calibrate your equipment. You can do this and have the owner drive the car enough to settle the suspension and come back for the alignment. Or, you can check for worn parts with the car on its tires. The 928 suspension is very robust and ball joints wear very little if the boots are intact.. Usually the first parts to wear and need replacement is the inner tie rod ends. Put the steering rack centering bolt in and shake the wheels to check. If one is bad, then it is best to replace both the inner and outer tie rod ends on both sides.
If you can't do alignment without lifting the car to accommodate your alignment equipment, then you probably should decline the job. It is not worth the hassle and you probably won't make much profit if you destroy the front tires and will have a very unhappy customer.
If you still want to do the alignment after lifting, there is a PORSCHE procedure to do this. It involves pulling the front of the car down by 60-70 mm and hold for 1 minute. After releasing, bounce front and rear approximately 25 mm a few times. The transport lugs or stabilizer can be used to pull the car down. If you plan to do this, I suggest that you check the ride height before lifting and then check before aligning to be sure that the measurements are the same. Probably the easiest way to check ride height is measure from the floor or turntable to the lip on the front fender at the center of the wheel. It should be about 27". The rear should be about 24.5". Many cars are lower. You can not settle a 928 by jumping up and down on the aluminum front fenders.
The rear suspension alignment is not affected as much by this lack of settling but will affect the front caster slightly if the rear is high and the front normal.
Caster is sometimes difficult to adjust below the maximum of 5 degrees ( spec is 4+1 degrees) on 1986.5 and later cars, but as long as the cross caster is within .2 degrees should be OK. The caster on 1986 and earlier cars is 3.5 to 4 degrees.
I will put the complete alignment presentation with pictures on a website when I get time.
Fibunits, If your front tires are not wearing, then he probably pulled it down before doing the alignment. Do the quick check posted earlier to find out. Or take it back to the alignment shop and ask him to just check toe-in without lifting the car. Make a copy of the following to give to the aligner.
WHY 928 SUSPENSION IS DIFFERENT THAN OTHER CARS 2
The PORSCHE 928 has very unique suspension bushings compared to other cars. If you jack up a 928 and let the wheels hang down, the bushings immediately take a "set". When you lower the car back down on its tires and roll the car back and forth to "settle" the suspension, the car will now sit ~1" higher than before it was jacked up. The car will now have to be driven up to 100 miles depending on how rough the roads are to settle the car back down to its proper height. The Porsche shop manual says "after a longer journey or longer operating period".
If you align the wheels with the car sitting 1" inch higher than the normal ride height, then, after settling, the front tires may be destroyed in less than ~1000 miles due to excessive toe out.
If you align the 928 with the car sitting 1/4" inch higher than normal, then, after settling, there will be no toe-in and the tires may be destroyed in ~2500 miles.
ALIGNMENT SHOP SUGGESTIONS
Normally one of the first steps in alignment is to jack up the car and check for worn and loose parts and calibrate your equipment. You can do this and have the owner drive the car enough to settle the suspension and come back for the alignment. Or, you can check for worn parts with the car on its tires. The 928 suspension is very robust and ball joints wear very little if the boots are intact.. Usually the first parts to wear and need replacement is the inner tie rod ends. Put the steering rack centering bolt in and shake the wheels to check. If one is bad, then it is best to replace both the inner and outer tie rod ends on both sides.
If you can't do alignment without lifting the car to accommodate your alignment equipment, then you probably should decline the job. It is not worth the hassle and you probably won't make much profit if you destroy the front tires and will have a very unhappy customer.
If you still want to do the alignment after lifting, there is a PORSCHE procedure to do this. It involves pulling the front of the car down by 60-70 mm and hold for 1 minute. After releasing, bounce front and rear approximately 25 mm a few times. The transport lugs or stabilizer can be used to pull the car down. If you plan to do this, I suggest that you check the ride height before lifting and then check before aligning to be sure that the measurements are the same. Probably the easiest way to check ride height is measure from the floor or turntable to the lip on the front fender at the center of the wheel. It should be about 27". The rear should be about 24.5". Many cars are lower. You can not settle a 928 by jumping up and down on the aluminum front fenders.
The rear suspension alignment is not affected as much by this lack of settling but will affect the front caster slightly if the rear is high and the front normal.
Caster is sometimes difficult to adjust below the maximum of 5 degrees ( spec is 4+1 degrees) on 1986.5 and later cars, but as long as the cross caster is within .2 degrees should be OK. The caster on 1986 and earlier cars is 3.5 to 4 degrees.
12-12-2002, 09:48 PM
#12
Nordschleife Master
Thread Starter
I was standing about 3 feet away from the guy while he did it. Well, most of the time. When he did the rear alignment I was under the car. He did NOT just any form of straps to cut it down. He also did NOT put the jacks on the ball joints. I think. I recall seeing them on the lift points.
The job came with a 6 month alignment waranty. If it's off they redo it for free. Nice uh?
I need something to point to thats more than just opinions of the 'net. I'm going to try to get a copy of the factory manual on the deal, and take it in. He has it on his computer that he's suppost to pick the frount end up. I have to argue not only with his experence, but with his computer too. I want air tight documentation before I try to say anything.
Course if I've got even tire wear, why bother?
The job came with a 6 month alignment waranty. If it's off they redo it for free. Nice uh?
I need something to point to thats more than just opinions of the 'net. I'm going to try to get a copy of the factory manual on the deal, and take it in. He has it on his computer that he's suppost to pick the frount end up. I have to argue not only with his experence, but with his computer too. I want air tight documentation before I try to say anything.
Course if I've got even tire wear, why bother?
12-12-2002, 11:18 PM
#13
Burning Brakes
The service manual states that the car MUST be pulled down before the alignment can be done. Also, the gas tank is supposed to be full, and weights should be placed on the driver's seat. Also, the tire presures need to be within factory spec, as should the ride height. This is all detailed in the service manual. A tech who aligns 928s should know this by heart.
If he doesn't, find one who does. YMMV.
If he doesn't, find one who does. YMMV.
12-12-2002, 11:50 PM
#14
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VU stated:
"I need something to point to thats more than just opinions of the 'net. I'm going to try to get a copy of the factory manual on the deal, and take it in."
If you can't use "opinions of the net" then why ask the net. The first thing that any 928 owner MUST have before working on his own car are the factory manuals.
"He has it on his computer that he's suppost to pick the frount end up." READ my previous posts. "I have to argue not only with his experence, but with his computer too." Read my previous posts. If you check it yourself before you take it back then there is no argument. "I want air tight documentation before I try to say anything." Buy the manuals.
"Course if I've got even tire wear, why bother?"
Good question. Why are you bothering us?
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"I need something to point to thats more than just opinions of the 'net. I'm going to try to get a copy of the factory manual on the deal, and take it in."
If you can't use "opinions of the net" then why ask the net. The first thing that any 928 owner MUST have before working on his own car are the factory manuals.
"He has it on his computer that he's suppost to pick the frount end up." READ my previous posts. "I have to argue not only with his experence, but with his computer too." Read my previous posts. If you check it yourself before you take it back then there is no argument. "I want air tight documentation before I try to say anything." Buy the manuals.
"Course if I've got even tire wear, why bother?"
Good question. Why are you bothering us?
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12-13-2002, 12:07 AM
#15
Burning Brakes
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The current Hunter alignment system tells the technician each and every step by step procedure to perform. I watched my guy roll the car forward or back per the instructions. He did not lift the car. He asked me to come back in a couple of weeks to check the front end after it had settled. (An alternative method is to pull down the suspension with hooks and pneumatic mechanisms.) It needed further refinement then. He gave me a color printout of how everything was in the green, with the associated numbers. I wonder if it would print out the procedures too.
Maybe your guy used the software. Maybe he has not paid for an upgrade. Maybe there are more than one ways to skin a cat.
Why not ask the guy nice about his methods? Our tires are extremely expensive. He might just give you a straight answer. He might agree to redo it. You can get the specs, and ask him to prove that his printout is in accordance.
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" />
Maybe your guy used the software. Maybe he has not paid for an upgrade. Maybe there are more than one ways to skin a cat.
Why not ask the guy nice about his methods? Our tires are extremely expensive. He might just give you a straight answer. He might agree to redo it. You can get the specs, and ask him to prove that his printout is in accordance.
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" />