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I know you can tell if a wheel hub stud is damaged based on the condition of its threads. However I have also seen people say you cannot tell the condition of a stud based on visual inspection alone, as they maybe fatigued or stretched.

  1. Is there a difference between a fatigued and stretched stud, if yes what is the difference?
  2. How can one tell if a stud is fatigue or stretched?
  3. If one or a set of studs have been fatigued or stretched due to over or under tightened wheel nuts but the studs have not snapped yet, if I then set them to the correct torque\tightness, will this prevent the studs from snapping, or is it too late and they will eventually snap regardless of whether you now start torquing correctly?
  4. If the answer to 3 is they will eventually snap, I guess this is something that one should immediately check before or after buying a used car since nobody knows if the previous owners have been torquing correctly etc?

Thanks

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1) & 2) yes, a stretched stud is longer and with correct kit you could measure the change. Fatigue is more challenging but use of crack detection is possible.

3) & 4) once damaged, the damage is not reversible, so replace all the studs and then you start from a known position.

Re 1) you can sometimes see a stretched stud as the thread pitch changes - but not always...

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  • Mike, with regards to 3, you mentioned that the damage is not reversible, however my question was provided an already irreversibly damaged(fatigued or stretched) stud is torqued properly from now onwards, will it prevent further damage which means the stud will not break, or will they eventually break anyway regardless of whether they stat to be torqued down properly? This way one cannot say it was the last mechanic that didn't torque your wheels improperly, it could have been a previous mechanic. thanks
    – James Wilson
    Aug 18, 2018 at 10:49
  • @JamesWilson what Mike is saying is that, if you know it's been damaged, replace it. Once a metal part is damaged, fatigue means the chance of it failing completely is much higher, and you really don't want to take the risk of your wheels falling off...
    – Nick C ♦
    Sep 17, 2018 at 8:50
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The easiest way to check whether a stud is stretched is to attempt to screw a nut onto it. If it screws all the way, the stud is fine. If it starts binding, the stud is stretched. If it's stretched, it WILL break at some point. The question is whether it'll happen at the workshop or on the side of the road in the middle of nowhere while you're changing a flat.

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