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Old 06-21-2011, 11:57 AM   #18
BYprodriver
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Join Date: Oct 2008
Location: O.C. CA
Posts: 3,709
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90% of the time your steering wheel shimmys at some speed but not others, it is caused by imbalance in the wheel/tire assembly. Rear tires affect the rear of the chassis & vibration can be felt in the seats. OK to check for wheel/tire imbalance remove other variables by setting tire PSI to vehicle manufacturers cold spec. Drive car on highway 5+ miles to get tires warmed up to operating temp. Now drive car to the smoothest, flatest road you can find. Any steering wheel can jump around if the road is rough enough. Drive at varing speeds to test for vibrations (I do this after any tire work/balancing to insure work is done properly, at night when it's quiet) 60-75mph seems to be the most critical speed. This establishes your baseline, if you have vibration on a smooth road you have a problem that needs to be resolved. When your tires are being balanced, WATCH to see it's done properly, Hi-perf tires on Porsche wheels should not require more than 2.5oz to balance. Watch the wheel spin on the balancer, if it hops up & down the wheel is probably bent & will hop up & down on your car too. If you see this ask them to remove the tire & spin balance the bare wheel to see how far out of balance your wheel is. I try to have this done before the tire is installed the first time so I know the condition of my wheels.
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