4/5 wheel studs busted...

[bergers59]

A friends car sheared 4 of the 5 wheel studs off in the rear of his 66 chevelle. The axles were moser with what I think are 1/2 studs(not sure) and weld racing wheels. I personally believe that the studs broke mainly because the wheel is supported by only by the studs since he is running 1/2 spacers, when I thought most of the weight is supposed to be carried by the center of the wheel. He believes that the only reason the studs broke off was due to the nuts being loose because the wheel was squeaking. This may be true, however I think it is a small component of why they failed that badly. Any thoughts, experience, or guesses as to what happened?

[Apogee]

I agree with your friend, loose and/or under torqued wheel studs will introduce a reversing combined loading scenario on the wheel studs due to the rotation of the wheel that will cause almost immediate failure due to fatigue. The axle register is there to locate the drum or rotor, not support the weight of the car. Most of the older muscle cars used 60 degree conical seat lugnuts to locate the wheels, not hub-centric designs. When a wheel stud is properly torqued, 85-105 ft-lb for a 1/2-20 stud, it won't see any internal stresses other than those induced by the preload until the external loading exceeds the existing stresses, which should not happen if everything is sized properly. This means that the wheel studs are in pure tension, and the clamping force between the mating surfaces of the wheel and drum/rotor are what keep the wheel located. While it may not make intuitive sense, simply stated, that's the way it works.

Larger diameter wheel studs require higher torque values, increasing the clamping forces between wheel and hub, thereby increasing the load capacity. Impact loading, such as launching at a drag strip with wrinkle wall tires, can change the picture a bit and require larger studs than would normally be required for a given application, but the principles are still the same, just a bit more complicated.

Tobin
KORE3

[Bob in St. Louis]

That's one of the most intelligent, well written posts I've ever seen on the internet.

[TheJDMan]

I agree!

[Dave Pratt]

I'm with the other two guys...great response...

[MonzaRacer]

Several points before I read others, :
One) Spacers should be hub centric, and have a hub also. Wheels studs should be torqued multiple times till no more lossening.
What took this wheel off was the wheel/spacer turning against the stud, bends and shears at axle level.
I would really prefer to use a proper seat lug but but with a shank that would reference inside the spacer.
While some must use spacers I am more intent on using bolt on spacers, properly torqued possibly reference pinned and with comparable studs installed. Also I prefer a hub centric , bolt on spacer.
The lugs above did shear due to lack or release of wheel torque and wheel and spacer twisting, ORoverly stretched studs failing in shear.
Still owner needs to reevaluate fasteners , torque , spacer use, and possibly antiseize on threads too gain more accurate torque. Silver type doesn't change torque spec, just would assure its consistency every time till lugs are worn out or damaged.

[bergers59]

Awesome, that's exactly what I was looking for. I'll let him know and help him fix it, thanks guys.

[Mr Nick]

Tobin in my brakes and all things related hero.