LVDell

So this past week at the track I noticed an odd sound coming from the front wheel carrier as I was pulling into the pits. Almost sounded like a bearing going bad. To check things out (after giving it the wheel shake test) I jacked up the car to dismount the wheel and take a look around. When I did I noticed that almost all my wheel nuts were loose (on all wheels). Not just loose but 4 of the 5 (on each wheel) about to back off the studs. That was sofa king scary when I thought about the session I just had and what could have gone wrong! Nuts were torqued to 96 and double checked before the session.

Anyway, I marked all my studs when I installed them and it looks like several of them have moved thus allowing the nuts to start backing off.

Any idea how they moved?

I torqued them down to 15 ft-lb when I installed them and even let them sit for a few days before mounting the wheels. Further I used Permatex 27200 High Temp Thread Locker Red.

Could the brake temps have destroyed the bond and allowed them to back out?

Rob S

Dell,

I hope you find the answer. I've been interested by recent reports of wheel attachment problems.

Were any of the other wheels loose? Is there any chance that you actually didn't torque that particular wheel properly, even though you'd swear on a stack of Bibles that you did? I've done things like that -- I'll "recall" having done something that's so automatic that I can't distinguish an actual occurrence from one of habit. If there's any chance that you goofed in this case, then that's a very logical explanation for what happened.

I can't understand why the studs would ever back out of the hub if the wheel studs and nuts maintain their clamping force. Thread locker shouldn't have any effect on maintaining wheel torque - you shouldn't even need thread locker except to keep the studs from backing out during loosening of the wheel nuts. It seems that a backed out stud would only happen *after* bolt preload is already lost for some other reason, the most likely of which is that the nuts were not torqued properly and they backed off (or the stud/nut backed off) during wheel rotation. The other possibilty is that something in the wheel attachment system yielded and allowed the clamping force to be lost, though this seems particularly unlikely if these are well used wheels in a tried-and-true system.

The fact that the studs rotated suggests that the strength of the thread locker was either lowered from brake heat or exceeded by forces imposed by an already loose wheel. That is, I think the rotated studs were a result of the problem, not the cause.

One thing you might already have thought of: I'd suggest replacing the studs on that wheel. They've now seen fatigue loads they weren't designed to see. I'm wondering if recent reports of wheel stud failures are because of incidents like this, where a wheel comes loose for some reason and then the owner just retightens the wheel and goes back on the road (or track) and forgets that it ever happened. It's during that loose-wheel-wobbling phase that a nearly invisible fatigue crack could form and start to grow, causing failure at a later date.

Rob

Boinkus44

Wow Dell, that's a weird one, and more than a little disconcerting. The fact that it was more than one stud that loosened would suggest that it is a macro sort of issue, along the lines of your theory about brake heat. Can't say I've ever heard of this issue before, but I'm going to be at my race shop tomorrow (coincidentally picking up the 3 after having the studs replaced) and I'll ask if they have ever heard of this. Definitely time for new studs though....

996FLT6

Can every street driving be the culprit on studded cars? Street roads are not exactly smooth. Mike

FFaust

Agree with all that Rob has said above. Specifically that thread lock should not make a difference to a well torqued wheel.

So Dell, 16 of the 20 nuts were loose?

Is is possible that you put the nuts on, and then lowered the car to the ground to torque them, but that the wheels were not properly seated before you lowered the car?

Although not as critical on our 5-lug cars, there is a reason why the procedure for the CL wheels on the .2 requires the wheels to be torqued off the ground. Just saying

Dudley

Same experience a friend had at the Glen last week.

SH || NC

I have the same studs as Dell, same nuts, even the same wheels, used Red, but have had no problems.....I do not however drive flat out in a TT.

LVDell

My wheels are always bolted down with the car in the air and then torqued checked once the car is back down off the lift.

There were about 1/2 go the nuts loose and about 1/4 of the studs showing movement from original position.

Maybe it's because I drive......

AudiOn19s

I've got nothing, after all these recent threads I'm keeping my damn wheel bolts and not installing studs. Seem like a real headache for most everyone.

joeycannoli

Going to go home and check my studs tonight...

SH || NC

Only guess I have it bad threadlocker....

You have to keep things in perspective though; we only hear about the bad stuff here. No one come back from a track weekend and talks about how their studs performed flawlessly!

Leigh2

I haven't had any trouble with studs coming loose on either the race car or the street car, but I'm changing wheels on both quite frequently so lots of re-torquing. I think the key with any car driven on the track is to check the torques frequently. All those heat cycles expanding and contracting of the wheels has to have an effect....

Mike in CO

Is it possible that a problem has developed with your torque wrench?

Burger

The only thing I can think that would cause all 5 to be loose would be if when they were torqued, the first one was not perfectly centered, and they all 'false' torqued without the ball seat actually making full contact.

It's highly unlikely that with even one stud breaking thread lock, that all would come loose at the same time.

Burger

To add, when I put my wheels on, I finger tighten one lug/stud and wobble the wheel a little to get it to center before torquing anything down.