Corner Balance Question
10-01-2009, 06:18 PM
#18
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Just a thought.
Check you have no broken springs (look right at the base of the coil where it sits in the perch)
Check that the ride height adjusters are within a millimetre or two of the same height above the base of the shock at each side. It is possible to get the ride height correct while having the car sitting mainly on one front wheel and it's diagonally opposite rear. Porsche springs are fairly accurate compared to most and it has been reported here that if the ride heights are equal side to side the corner weights will be within 25lbs or so.
Check you have no broken springs (look right at the base of the coil where it sits in the perch)
Check that the ride height adjusters are within a millimetre or two of the same height above the base of the shock at each side. It is possible to get the ride height correct while having the car sitting mainly on one front wheel and it's diagonally opposite rear. Porsche springs are fairly accurate compared to most and it has been reported here that if the ride heights are equal side to side the corner weights will be within 25lbs or so.
10-01-2009, 07:00 PM
#19
Rennlist Member
actually, I think rear alignment is REALLY important, and one of the reasons the Holbert car never really acted like my older 928, even though it did handle well, it just had a lot of push. Im finding out from experts that as little as 1/16 " in the rear toe area, going toward toe out, makes a huge difference in oversteer, and getting rid of a push, and getting the car to rotate. certainly, in my next car, my rear toe will be set at 0. 
one of the reasons you ran faster with the 300lb guy, was probably you were amped up with someone in the car with you. normally, the weight will hurt accel, braking and cornering all pretty dramatically. You were probably doing what you are talking about, by driving around the problem and driving or pushing even harder!
mk
one of the reasons you ran faster with the 300lb guy, was probably you were amped up with someone in the car with you. normally, the weight will hurt accel, braking and cornering all pretty dramatically. You were probably doing what you are talking about, by driving around the problem and driving or pushing even harder!
mk
You make is sound as if rear alignment is not very important on your courses in a 928. I've always been told a good driver can make a fast car go fast, but a great driver can make a slow car go fast. Still doesn't stop me from wanting my car setup as good as it can be setup.
On our courses cornering is a big part of lap times. We try to set up our courses to balance out the advantages between high horsepower straight line cars and the quick in the corners low powered cars, ie., Vipers versus Miatas.
I've set FTD in my well setup 944 Turbo and then gave a 300 lb guy a fun run ride with the timers still on. We usually don't allow passengers with the timers on for insurance reasons. Anyway, with the 300 lb passenger I matched my previous official FTD time. On that fat lap my top speed at the end of the few straights was 10 to 15 mph lower due to the extra weight, yet the added weight increased corner speeds enough to make up the difference.
At that time with that car I was very adept at very late braking then initiating a 4 wheel drift on turn-in and maintaining that drift through the apex throttle steering and also through the exit until the car was pointed straight again. Being smooth made a huge difference and the rocking of the un-corner balanced setup made it a LOT more difficult to get into the 4 wheel drift consistently on entry. The car would break loose when it rocked on turn in lowering my entry speed to keep from understeering then oversteering as the car settled and rotated causing even more speed to be scrubbed off. I gained quite a bit of corner entry speed after it was balanced just from the added smoothness alone.
I am hoping my mechanic will learn how to align the dern thing so I will have somewhere I can take the car and depend on it being done right. He's had it on the rack 3 times now.
On our courses cornering is a big part of lap times. We try to set up our courses to balance out the advantages between high horsepower straight line cars and the quick in the corners low powered cars, ie., Vipers versus Miatas.
I've set FTD in my well setup 944 Turbo and then gave a 300 lb guy a fun run ride with the timers still on. We usually don't allow passengers with the timers on for insurance reasons. Anyway, with the 300 lb passenger I matched my previous official FTD time. On that fat lap my top speed at the end of the few straights was 10 to 15 mph lower due to the extra weight, yet the added weight increased corner speeds enough to make up the difference.
At that time with that car I was very adept at very late braking then initiating a 4 wheel drift on turn-in and maintaining that drift through the apex throttle steering and also through the exit until the car was pointed straight again. Being smooth made a huge difference and the rocking of the un-corner balanced setup made it a LOT more difficult to get into the 4 wheel drift consistently on entry. The car would break loose when it rocked on turn in lowering my entry speed to keep from understeering then oversteering as the car settled and rotated causing even more speed to be scrubbed off. I gained quite a bit of corner entry speed after it was balanced just from the added smoothness alone.
I am hoping my mechanic will learn how to align the dern thing so I will have somewhere I can take the car and depend on it being done right. He's had it on the rack 3 times now.
10-01-2009, 07:04 PM
#20
Rennlist Member
bottom line, just make sure that thing is settled. set your ride hight visually if you want, and then align it without lifting the car in anyway. if your guy cant do it, find someone that can. if you do, you will be quite happy with the handling. agressive setting, but not race would be 1.3 1.7 degree (f-r) camber .
Then, .15 degree toe in up front, and 0 to .10 degree toe in the rear.
Then, .15 degree toe in up front, and 0 to .10 degree toe in the rear.
10-01-2009, 07:25 PM
#21
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Thread Starter
No luck on swapping front wheels across still pulls to right with alignment measurements spot on. Mechanic measured height of fenders, put car on rack (lifting required), then pulled and bounced the car down to same fender heights before lifting. For some reason could not get rear toe correct, too much toe in. Claims it is at the limits of adjustment and that is with only .6 degrees negative camber rear. Seems every time he tries to align it it has more rear toe in and less rear negative camber. That combined with the pull the mechanic is getting very frustrated and has aligned a lot of 928s without issues like this.
Was shooting for f -1.5, r -1 camber and just less than 0 -toe front and rear.
Mark, so you are saying very much negative toe in the rear causes understeer?
Was shooting for f -1.5, r -1 camber and just less than 0 -toe front and rear.
Mark, so you are saying very much negative toe in the rear causes understeer?
10-02-2009, 01:31 AM
#23
Rennlist Member
you can pull and jump on the car as much as you want, til the cows come home and you wont get an alignment that works until you and your mechanic, do it by NOT raising the car. This is fundamental problem with alignments on 928s. If it pulls, its becuase the rear vs the front are not perfectly aligned.
do yourself a favor, go to a sears or some cheapo place that has a hunter machine and just drive the car on to the rack. zero out the wheel runnout by moving the car backward on the rack. see what the real alignment is
We have all been down this path before.
the only time my car has ever pulled was when I put on a 245 and a 255 on the front wheels and didnt notice the mistake until i hit the freeway.
mk
do yourself a favor, go to a sears or some cheapo place that has a hunter machine and just drive the car on to the rack. zero out the wheel runnout by moving the car backward on the rack. see what the real alignment is
We have all been down this path before.
the only time my car has ever pulled was when I put on a 245 and a 255 on the front wheels and didnt notice the mistake until i hit the freeway.
mk
No luck on swapping front wheels across still pulls to right with alignment measurements spot on. Mechanic measured height of fenders, put car on rack (lifting required), then pulled and bounced the car down to same fender heights before lifting. For some reason could not get rear toe correct, too much toe in. Claims it is at the limits of adjustment and that is with only .6 degrees negative camber rear. Seems every time he tries to align it it has more rear toe in and less rear negative camber. That combined with the pull the mechanic is getting very frustrated and has aligned a lot of 928s without issues like this.
Was shooting for f -1.5, r -1 camber and just less than 0 -toe front and rear.
Mark, so you are saying very much negative toe in the rear causes understeer?
Was shooting for f -1.5, r -1 camber and just less than 0 -toe front and rear.
Mark, so you are saying very much negative toe in the rear causes understeer?
10-05-2009, 10:51 AM
#24
Rennlist Member
Thread Starter
Quick update...
Alignment guy did not know had to unweight the suspension to adjust toe mounts to put the eccentrics in adjustment range. Will find out if that helps the situation.
Alignment guy did not know had to unweight the suspension to adjust toe mounts to put the eccentrics in adjustment range. Will find out if that helps the situation.
10-05-2009, 04:25 PM
#25
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Do you mean adjust the mounting position of the base of the shock to change the position of the caster and camber eccentrics?
I don't recall there being much tolerance in the position of the two fixed bolts that go through the LCA.
Something is wrong if you can't get the toe setting right.
The 928 way to do it is get the Camber correct first then adjust toe. Most alignment techs do toe first then adjust camber (which is normally miles out) and then have to re-adjust the toe a long way to deal with the big camber correction.
I don't recall there being much tolerance in the position of the two fixed bolts that go through the LCA.
Something is wrong if you can't get the toe setting right.
The 928 way to do it is get the Camber correct first then adjust toe. Most alignment techs do toe first then adjust camber (which is normally miles out) and then have to re-adjust the toe a long way to deal with the big camber correction.
10-05-2009, 04:43 PM
#26
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Thread Starter
When I first got the car I took it to the local dealer to have the ride height put to low end of spec and an alignment. They know the 928 well and have a flat roll on alignment rack. That dealer mechanic told me that he had to take the car off the alignment rake put the car on a lift to unweight the suspension and adjust the rear toe mounts then drive the car around to settle it then go back to the alignment rack to get the rear adjusted. Told me the rear toe mounts would not move if the weight was on the suspension. Cost me an extra $100 in labor. He apologized for the extra charge and said is was very rare that he had to do that. Again, Not the front, the rear.
The problems I am having now is with the local non-dealer porsche shop. They have been in the Porsche service business for as long as I can remember and I am 50 and have lived here in OKC for 49 years. They never had any problems aligning my 90 GT or many other 928s they service. Just seem to be having problems with this car. The dealer had aligned the car on the aggressive side of the stock tolerances. I ask the shop crank the front camber up to -1.5 and set the front and rear toe as close to zero as possible without being positive. Front camber was -.6 and rear camber was -.8 from dealer. It pushed/understeered mid-corner. Idea was more negative front camber and zeroing out the toe would take the push out.
I will hear back tomorrow if lifting to adjust the toe mounts worked for him.
The problems I am having now is with the local non-dealer porsche shop. They have been in the Porsche service business for as long as I can remember and I am 50 and have lived here in OKC for 49 years. They never had any problems aligning my 90 GT or many other 928s they service. Just seem to be having problems with this car. The dealer had aligned the car on the aggressive side of the stock tolerances. I ask the shop crank the front camber up to -1.5 and set the front and rear toe as close to zero as possible without being positive. Front camber was -.6 and rear camber was -.8 from dealer. It pushed/understeered mid-corner. Idea was more negative front camber and zeroing out the toe would take the push out.
I will hear back tomorrow if lifting to adjust the toe mounts worked for him.
10-05-2009, 04:50 PM
#27
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RKD,
You might go to my site for a refresher on 928 alignment. http://members.rennlist.com/captearlg/
It is probably too late, but this is my take on corner balancing: In the MISCELLANEOUS RAMBLINGS section.
CORNER BALANCING
I have found that when properly balanced, the spring perch adjustment nuts for most 928s are the same height on each side of the same axle. Apparently Porsche springs are very accurate. I therefore recommend that during ride height adjustments, you make the spring perch height the same on each wheel of the same axle. You may end up with the ride height slightly different from side to side, but the car will be close to corner balanced and the difference will not be visible. Keep in mind that the car is not the same weight on each side (passenger side heavier on LH drive cars) and the sway bars may not be perfect. Also, if you have Louie Ott drop links, un-bolt the lower rod end attachment from the lower control arm during ride height adjustments and adjust the length so that the bolts just slip on when you re-install them.
You might go to my site for a refresher on 928 alignment. http://members.rennlist.com/captearlg/
It is probably too late, but this is my take on corner balancing: In the MISCELLANEOUS RAMBLINGS section.
CORNER BALANCING
I have found that when properly balanced, the spring perch adjustment nuts for most 928s are the same height on each side of the same axle. Apparently Porsche springs are very accurate. I therefore recommend that during ride height adjustments, you make the spring perch height the same on each wheel of the same axle. You may end up with the ride height slightly different from side to side, but the car will be close to corner balanced and the difference will not be visible. Keep in mind that the car is not the same weight on each side (passenger side heavier on LH drive cars) and the sway bars may not be perfect. Also, if you have Louie Ott drop links, un-bolt the lower rod end attachment from the lower control arm during ride height adjustments and adjust the length so that the bolts just slip on when you re-install them.
10-05-2009, 04:59 PM
#28
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Thread Starter
Ride height is dead on low end of factory specs. On the scales it checked good so there were no adjustments made. I did the install of the Ott drop links for no preload.
10-05-2009, 05:00 PM
#29
Rennlist Member
not really true. Ive done a lot of cornerbalancing checking and have found that this might be true in the front, but the rear has a light corner, the side of the gas tank. anyway, its ony 2-3 turns off to get the cross weights near perfect. front to rear will never be perfect as the 928 is nose heavy.
RKD,
You might go to my site for a refresher on 928 alignment. http://members.rennlist.com/captearlg/
It is probably too late, but this is my take on corner balancing: In the MISCELLANEOUS RAMBLINGS section.
CORNER BALANCING
I have found that when properly balanced, the spring perch adjustment nuts for most 928s are the same height on each side of the same axle. Apparently Porsche springs are very accurate. I therefore recommend that during ride height adjustments, you make the spring perch height the same on each wheel of the same axle. You may end up with the ride height slightly different from side to side, but the car will be close to corner balanced and the difference will not be visible. Keep in mind that the car is not the same weight on each side (passenger side heavier on LH drive cars) and the sway bars may not be perfect. Also, if you have Louie Ott drop links, un-bolt the lower rod end attachment from the lower control arm during ride height adjustments and adjust the length so that the bolts just slip on when you re-install them.
You might go to my site for a refresher on 928 alignment. http://members.rennlist.com/captearlg/
It is probably too late, but this is my take on corner balancing: In the MISCELLANEOUS RAMBLINGS section.
CORNER BALANCING
I have found that when properly balanced, the spring perch adjustment nuts for most 928s are the same height on each side of the same axle. Apparently Porsche springs are very accurate. I therefore recommend that during ride height adjustments, you make the spring perch height the same on each wheel of the same axle. You may end up with the ride height slightly different from side to side, but the car will be close to corner balanced and the difference will not be visible. Keep in mind that the car is not the same weight on each side (passenger side heavier on LH drive cars) and the sway bars may not be perfect. Also, if you have Louie Ott drop links, un-bolt the lower rod end attachment from the lower control arm during ride height adjustments and adjust the length so that the bolts just slip on when you re-install them.
10-05-2009, 05:05 PM
#30
Rennlist Member
It sounds like this guy is completely lost. take it to a Hunter rack, no lifty and you will get a good alignment. adjsting, driving around, weighting the car, the guy is falling into the classic alignment mistake traps.
its real simple stuff. You have a standard road height car. very very easy to align, as long as the car hasnt been in a wreck or some parts are badly worn.
Trust me, ive been down all these roads before, and they all lead to frustration unless you listen to what we have all seen before. No lift, adust the alignement and you are good to go. Its that simple. no pulling, no tire wear, no weird handling, after its aligned properly, by someone that knows 928s
mk
its real simple stuff. You have a standard road height car. very very easy to align, as long as the car hasnt been in a wreck or some parts are badly worn.
Trust me, ive been down all these roads before, and they all lead to frustration unless you listen to what we have all seen before. No lift, adust the alignement and you are good to go. Its that simple. no pulling, no tire wear, no weird handling, after its aligned properly, by someone that knows 928s
mk