bry195
06-23-2012, 11:09 PM
So i have rims with the e39 pilot. They are new rims and came with the plastic hubcentric adaptors. After breaking a few of them i ordered the aluminum ones. They dont break. I wetstoned all of the mating surfaces so everything was flat, round and free of dents and dings. This was a days worth of work on this old car. Mounted the rims and they seemed to fit really well. I still had a couple small vibrations. What a bummer. Everything is new and matched really well.
Anyways, i use to repair machine tools so i decided to use some old skills i hadnt used in awhile. I put a dial indicator on the rims and found that even with the adaptors some of the rims were rotating about 1 mm off concentricly. There was about 1mm of runout on some of these rims mounted. So, i tightened all of the lug nuts to about 1lb of torque and tapped the rims with a hammer until i got them all to the best number i could get. All of the rims are now within 25 microns of total runout. .025mm or about .001 inches. I would never have thought that i would have had that much slop in the pilot and hub with the adaptors. Crazy. Anyways it was raining today so ill try to take it for a ride tomorrow but ill bet all the vibrations are gone. Im sure the 25 microns is the tolerance of the runout in the rim. Holding that kind of tolerance on a lathe while hogging aluminum off is pretty good.
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Anyways, i use to repair machine tools so i decided to use some old skills i hadnt used in awhile. I put a dial indicator on the rims and found that even with the adaptors some of the rims were rotating about 1 mm off concentricly. There was about 1mm of runout on some of these rims mounted. So, i tightened all of the lug nuts to about 1lb of torque and tapped the rims with a hammer until i got them all to the best number i could get. All of the rims are now within 25 microns of total runout. .025mm or about .001 inches. I would never have thought that i would have had that much slop in the pilot and hub with the adaptors. Crazy. Anyways it was raining today so ill try to take it for a ride tomorrow but ill bet all the vibrations are gone. Im sure the 25 microns is the tolerance of the runout in the rim. Holding that kind of tolerance on a lathe while hogging aluminum off is pretty good.
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