Thread: Alignment Issue
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      07-09-2009, 07:57 PM   #27
BMWM.D.
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Drives: E90 335i & 6th Gen ZL1
Join Date: May 2009
Location: Santa Barbara

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While I am glad to hear that you got the problem resolved, I can see a few things that might have caused the issue. Hopefully, this will prove useful to some of you guys who need alignments in the future.

Let me start by first saying that no E9x M3 has active steering. It is even a fairly rare option on regular 3 series. There should be no additional charge for aligning an M3.

First, all BMWs are supposed to be heavily weighted during an alignment procedure. It is supposed to be 150 lbs. in each front seat, 150 lbs. in the back seat and I believe 60 lbs. in the trunk. If the car was not weighed down, the settings will not be correct when the car is going down the road at speed.

Next, there is the fact that a car will always want to pull to the side with the most positive camber setting. From your first alignment spec sheet, the right side has more positive camber than the left (L -1.14 R -1.02 ). Most alignment machines read in degrees and minutes (ie. 60 minutes in a degree) , so your front camber setting was a quarter degree more positive on the right which could cause a slight pull/drift that direction.

Also, if the car was not weighted properly during the first alignment, it is likely that when you sit in the car the left front drops a bit and the negative camber increases even more (than what you see on the 1st printout), which would increase the cross-camber and make the pull situation even worse.

Pulls or drifts can also be caused by uneven tire wear, but it is usually a result of poor cross-caster or cross-camber. Toe will not cause a pull, but it can cause stability issues.

If the rear toe is off, it can cause a thrust angle problem which leads to "dog tracking". The front and rear axles are supposed to be parallel to each other and perpendicular to the vehicle centerline. If the toe is off on one of the rear wheels, the thrustline changes. Toe will always want to equalize itself when driving, so guess what happens when the rear axle is no longer aligned with the front properly? The car drives sideways down the road and the result will be a crooked steering wheel and excessive tire wear.

Make sense?
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