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M3 Track: Racing and DE Best mod for speed is learning to get the most out of what you currently have. Tracks and DE's is the place to start!


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Old Tue, Jun-11-2019, 08:20:47 PM   #61
pMak26
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Default Re: Wheel Stud Life Span?

Happy to share this Torque Chart (pdf attached).

A LOT depends on if you lubricate the stud as well. I like to use just a bit of copper grease on my studs to prevent galling. In this case that would constitute a "well lubricated bolt" as shown on the second chart in the pdf.

A well lubricated M12 10.9 is torqued to 66 lbft.

A dry M12 10.9 calls for 88 lbft.

That's a substantial difference. If there happens to be assembly grease or some kind of lubricant on your studs from manufacturing/shipping/storage and you are torquing up to 88-90 lbft, I could understand why the studs are breaking.
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File Type: pdf Torque Chart.pdf (543.2 KB, 10 views)
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Old Tue, Jun-11-2019, 09:09:52 PM   #62
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Default Re: Wheel Stud Life Span?

The standard 'reduce by 15% if lubricated' applies.
BMW spec (E36) is 90-110Nm dry, so taking the middle ground, that means:

Dry: 100nM, 74 ftlb
Wet: 85nM, 63 ftlb
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Old Wed, Jun-12-2019, 07:45:00 PM   #63
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Default Re: Wheel Stud Life Span?

I swap street wheels onto my car at the end of the day when the studs are hot.

How much should I lower my torque value to account for the metal contracting as it cools?
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Old Wed, Jun-12-2019, 07:49:02 PM   #64
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Default Re: Wheel Stud Life Span?

I forgot to look into that.

I figure though that if you wait until the studs and lugs are comfortable to touch, you can use full torque.
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Old Wed, Jun-12-2019, 08:11:59 PM   #65
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Default Re: Wheel Stud Life Span?

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Originally Posted by nholmes View Post
I swap street wheels onto my car at the end of the day when the studs are hot.

How much should I lower my torque value to account for the metal contracting as it cools?
I doubt there's a simple answer to that. The thickness of the wheel will change with temperature, along with the length of the stud.
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Old Thu, Jun-13-2019, 01:14:50 AM   #66
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Default Re: Wheel Stud Life Span?

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I doubt there's a simple answer to that. The thickness of the wheel will change with temperature, along with the length of the stud.
Fair.

Maybe a ballpark? "Reduce the torque amount by 10%" or something?
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Old Thu, Jun-13-2019, 02:17:34 AM   #67
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Default Re: Wheel Stud Life Span?

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Originally Posted by nholmes View Post
Fair.

Maybe a ballpark? "Reduce the torque amount by 10%" or something?
If just driving home? I'd probably start at 20% low, then measure once cool. Adjust from there. That's without any analysis at all obviously.

The problem with picking A number is that it may make a big difference depending if your studs/wheels are 350 degrees or 200 degrees, meaning something as simple as your cool down lap and time to put the car up on a jack stand could make a difference.
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Discussing Wheel Stud Life Span? in the M3 Track: Racing and DE Forum - Best mod for speed is learning to get the most out of what you currently have. Tracks and DE's is the place to start! at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)