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Wheel spacer test to prevent wheels falling off at the track

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Dave_W

Cones - not just for ice cream
984
1,277
Exp. Type
Autocross
Exp. Level
20+ Years
Connecticut
The amazing part is that even a well-funded professional team with expensive wheels can suffer this issue. Everyone should do this test, and do it for all the combinations of their wheels & spacers.
 
A couple of comments on this subject. We've never seen a stud failure due to this particular problem, because we've never seen this interference problem before.

All OEMs have radius/chamfer specifications for the bore in the wheel and for the base of the hub pilot. If wheel spacer manufacturers simply followed these, this problem could never occur. The wheel spacers that Chris shows in the video are incorrectly designed. The radius at the base of the hub pilot should never be this large. A small radius here does not create a stress riser, because the only stress on the wheel spacer hub pilot, is when the wheel and tire are hung on it, before the lug nuts are tightened. Once the lug nuts are tightened, the chamfer between the lug nuts and wheel stud holes centers the wheel and all load on the hub pilot is zero.

The only possible issue here is that if there is a chamfer on the back side of the thru hole in the spacer, you may need to put a larger radius at the base of the hub pilot on the wheel side of the spacer, so that there is enough material thickness. This effectively puts a limit on how thin of hub centric wheel spacer one can build.

The types of wheel stud failures that we have seen are caused by a similar issue. The hub pilot on a hub centric wheel spacer has a particular length and OD. Some wheels (Enkeis are the worst about this) have a smaller thru hole in the wheel center, designed to fit their cap on the outside. Inside this, on the hub side, is a counterbore for the hub pilot. This hub pilot counterbore is not deep enough to fit on many Ford 5 x 4.5" applications, without the hub pilot bottoming out at the end of the counterbore. When used with hub centric wheel spacers, the same problem exists. The solution is to file about 0.060" off of the tip of the hub pilot on the wheel spacer.

I believe that most 5 x 4.5" Enkei wheels are designed around a Toyota application, which is why they have such a large counterbore in them (>2.775"). This application must have a shorter hub pilot than Ford uses on a Mustang. Enkei should be maching the hub pilot counterbore deeper, so that it is compatible with Ford axles and hubs. I've brought this up with them on a couple of occasions at SEMA. They don't seem to care.



Chris' paper test will work to test for both cases of improper wheel spacer fitment.
 
106
52
Exp. Type
HPDE
Exp. Level
5-10 Years
So CA
A couple of comments on this subject. We've never seen a stud failure due to this particular problem, because we've never seen this interference problem before.

All OEMs have radius/chamfer specifications for the bore in the wheel and for the base of the hub pilot. If wheel spacer manufacturers simply followed these, this problem could never occur. The wheel spacers that Chris shows in the video are incorrectly designed. The radius at the base of the hub pilot should never be this large. A small radius here does not create a stress riser, because the only stress on the wheel spacer hub pilot, is when the wheel and tire are hung on it, before the lug nuts are tightened. Once the lug nuts are tightened, the chamfer between the lug nuts and wheel stud holes centers the wheel and all load on the hub pilot is zero.

The only possible issue here is that if there is a chamfer on the back side of the thru hole in the spacer, you may need to put a larger radius at the base of the hub pilot on the wheel side of the spacer, so that there is enough material thickness. This effectively puts a limit on how thin of hub centric wheel spacer one can build.

The types of wheel stud failures that we have seen are caused by a similar issue. The hub pilot on a hub centric wheel spacer has a particular length and OD. Some wheels (Enkeis are the worst about this) have a smaller thru hole in the wheel center, designed to fit their cap on the outside. Inside this, on the hub side, is a counterbore for the hub pilot. This hub pilot counterbore is not deep enough to fit on many Ford 5 x 4.5" applications, without the hub pilot bottoming out at the end of the counterbore. When used with hub centric wheel spacers, the same problem exists. The solution is to file about 0.060" off of the tip of the hub pilot on the wheel spacer.

I believe that most 5 x 4.5" Enkei wheels are designed around a Toyota application, which is why they have such a large counterbore in them (>2.775"). This application must have a shorter hub pilot than Ford uses on a Mustang. Enkei should be maching the hub pilot counterbore deeper, so that it is compatible with Ford axles and hubs. I've brought this up with them on a couple of occasions at SEMA. They don't seem to care.



Chris' paper test will work to test for both cases of improper wheel spacer fitment.
Interesting, any diagrams to illustrate this? I’m a bit lost.

I’m using 25mm spacers on my Apex front wheels 52mm offset which many are using for the square setup.
 
334
352
The bimmerworld video is good, and safety testing is always a good thing, but my understanding is that broken studs are a much bigger issue with BMWs because so many of those guys use aftermarket thread in studs. The press in stud design used by Ford and a lot of other OEMs is supposedly much better in this regard.

I do a lot of track days with my BMW friends and have seen a number of BMW stud failures but not on other makes. The BMW guys who really take this seriously use this kit:

 
Thanks Ludachris for posting this, I saw this video here on TMO last summer (?) and checked all my front spacers this way and it worked well and nice to confirm! (Using 25mm OMP spacers with Apex 18x11" wheels.)

I'll share something related I found when I started using these Apex wheels... While installing one of the rears, I noticed that one of my ARP studs didn't stick out of the Gorilla lugnut as far during the hand-tightening phase. Long story short, there was a nick on rear axle/hub that was sticking up and wouldn't let the Apex wheel seat properly. I had to file it down and also clean up the inner hub of the wheel a bit. So, shows the tight tolerances on the Apex wheel, and something I continue to be careful with when I install the wheels. >The never gets old lesson: if it seems "off" it probably is!
 

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