CaptainGSR

I just bought a new 21" sport plus rim from my local dealer.
Upon installation, my independent shop noticed that it was clearly out of round.
I measured the lateral rim runout at approx .035 in = .889 mm.
This seemed outrageoulsy excessive to me, so I went back to the dealer.
They said that the rim was fine according to their hunter balancing machine. They also said that if they ordered another rim it would probably be just as bad.
I don't have a Cayenne service manual. Can someone tell me what the max permissible runout is?
The max allowable runout for my 993 is .7mm! My worst rim measures at .2mm!

Cheers,

CaptainGSR

After much digging, I finally found the info online.
It is straight out of the 9PA Cayenne Manual (p1183).
I was measuring the outside edge. My inside edge measures at 0.2-0.3mm.

I hope it helps:


Wheels: Testing and Inspection

WM 440002 Checking disc wheels

Checking the radial and lateral runout

Information
Straightening and welding work on light alloy wheels is not permissible.

The work is carried out initially with the wheel mounted on the vehicle.
-
To measure wheels with tires and wheels without tires, use a tire measuring gauge, e.g. VAG. 1435.

Maximum permissible radial runout and lateral runout of the wheel with tire = 1.25 mm. Values less than 1.0 mm - better around 0.5 mm - are
desirable. For this purpose, match the tire (turn the tire on the rim) if necessary.).

Maximum permissible radial runout and lateral runout -a- of the light alloy wheels = 0.7 mm.

If in isolated cases further measurements are necessary, carry out the following procedure.

1. To measure wheels without tires, remove the wheel from the vehicle.
2. Remove the tire from the light alloy wheel.
3. Clamp the wheel on the balancing machine and measure at points -a-

deilenberger

Johan - 0.2mm = 0.007874" - ie - is a bit more than 7/1000th of an inch. That would be well within any tolerance for any wheel. The outside variance seems well within the differences in paint thickness that might be found on the edge of the rim. Typically the outside edge is left as "cast" (or forged) while the inside edge is machined.

CaptainGSR

Yes, I agree.
After measuring the inside (-a-), I decided to keep the rim.
Cheers,

CaptainGSR

Just an update.

Upon further inspection of the 21" rim without tire installed, we found that there was indeed a problem with the casting of the outside lip.
The outside lip is not of a uniform thickness. While the part of the lip in contact with the tire is perfectly machined (inside and top surface), the visible (outside) part of the outside lip is uneven (thicker by just under 1mm for about 4 inches).

Deilenberger, you were spot on!

The dealer thinks that it should have no noticeable effect on the balancing, and that my old tire was out of round, therefore causing the vibration.
The new rim+old tire combo measured at 20 on the Hunter Road Force.

We'll see what a new tire does. I am skeptical!
I can't say that I am too impressed by the casting process on these large rims...

John Rose

We have a wheel guy in Northern California who checks the out of round condition every time he puts new tires on a car . He says most cars have out of round rims after they hit the first pothole . He checks it with a dial Indicator and has a machine to put the wheel back round again . I had HRE rims on my 911 turbo and after 6 years he said they were perfect .

CaptainGSR

Well, I can tell you that I will never ever buy rims at a dealer again. I am done with that expensive cast garbage.
Next time it will be cheap and direct from a third party, or I'll splurge for forged.
My LMs are also almost 10 years old and still perfect. I also like HREs!