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General >> Rally >> Shearing off the wheel studs?
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Message started by overthehill on 12/03/8 at 16:14:59

Title: Shearing off the wheel studs?
Post by overthehill on 12/03/8 at 16:14:59

It seems that wheel studs have a tendency to shear off here and there (e.g. Antoine, John, etc). I have just sheared off two out of four on my dolly – not a very pleasant discovery when your car is on the dolly. >:(

The studs we used were hard ones and they basically snapped off (as if you over tighten the lug nut and snap the stud – but that is not what happened, they sheared off as I was driving).

Should we use softer studs (presumably not as brittle as the hard ones)? Anybody has any experience and was able to solve this issue?

Thanks for any advice,

Paul

Title: Re: Shearing off the wheel studs?
Post by dtompsett on 12/03/8 at 16:36:39

The key thing here is not over-tightening the lug nuts. A harder stud means it won't stretch/bend/break until a higher point... but they are often more brittle. So when you overtighten them, they are likely to snap instead of stretch.

A soft stud will stretch before it snaps... but it becomes a never-ending battle. The metal reaches a critical strength when stretched just the right amount (think... stretching head bolts to the proper spec)... but if you over-tighten, then they go beyond the yield point and become weaker. If you tighten beyond that optimal stretching (tensile) stress, the metal will continue to stretch and you will never get them perfectly tight again, and they will stretch with less tensile stress until they break.

That's why you need to use new head bolts when you do a head gasket.

If you've cranked down those lug nuts with an impact gun, you've probably overtightened them, and stretched the studs (which keep stretching until they break). Thats why you need to be sure your tire shop doesn't let some lazy kid use an impact gun to crank down those lug nuts.

That said... I've never broken a lug stud/bolt, except when held in by YEARS of rust.

Softer is also more likely to stretch, so you have to keep checking torque values.
Harder is more brittle, but less likely to stretch.

Just replace them with the normal studs... and replace the ones that didn't fail as well... since they probably stretched.

Title: Re: Shearing off the wheel studs?
Post by Oddball343 on 12/09/8 at 19:57:33

we've had a few break on our Corvettes at Mosport (including multiple breaks at once going into turn 8 ...... which ended up in the tire wall). After sending the broken ones away for analysis it came back that they were undertorqued. We used GM racing ones.

Title: Re: Shearing off the wheel studs?
Post by Robin_Fleguel on 12/10/8 at 09:51:28

Tirerack recommended 'torques'
M12, 70-80 ft-lbs
M14, 85-90 ft-lbs

Robin

Title: Re: Shearing off the wheel studs?
Post by xrian on 12/10/8 at 10:39:52

For you guys who have been breaking studs, are your rims not hub-centric?
I make sure that all the wheels we use are hub-centric and we also use ARP studs. Never had a break.