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      11-12-2012, 08:39 PM   #23
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Drives: 2011 Z4 3.5i
Join Date: Jul 2011
Location: Greenville, SC

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Originally Posted by jpwolfe31 View Post

6) Z4 296 wheel rims do not fail on their own. They are damaged by impacts which cause cracking.
7) The UK's position to replace wheel rims stipulates that only when a rim is found to be cracked WITHOUT visual damage. The rims found on this vehicle were visually damaged as could be seen by the runout ( bending) of the rims when they were rotated on a wheel balancer.
One important question to all cracked rim sufferers; was the tire removed from the rim before they did the runout measurement or did they do the measurement on the tire/wheel assembly? A cracked rim has lost a large amount of it's strength and it wouldn't surprise me if the rim was bent in the tire machine when they removed the tire, especially removing a run-flat tire with a very stiff side wall. This could be why your car didn't vibrate at 70 with the cracked rims. If (when) mine crack, I will insist that they do the runout measurement before they remove the tire from the rim. I'll also do the measurement and video the indicator reading before I take the car in (like that will do any good but it will make me feel better).

Also, BMW is assuming that the wheel is out of round because of an impact but could it be that since the rim has lost much of it's strength after cracking, that the rim went out-of-round over small bumps due to the weakening of the rim after the crack and not because of an impact??

And do they have a reasonable explanation as to why it is almost always the rear rims that crack and not the front? Seems kind of ludicrous of BMW to think that people only hit pot holes and curbs with the rear wheels and not the fronts.