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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Tracking, Autocrossing, Dragstrip, Driving Techniques > Track torque for wheel lug bolt? Thread lock or no?



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      09-25-2013, 04:30 PM   #1
labedra
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Track torque for wheel lug bolt? Thread lock or no?

Hey guys, I started tracking my car, I tighten my wheels to 90 ft/lb before and after 30 min session, after the car wheels cool down. Last 30 min session i forgot to retighten the bolts and drove home and my wheels became loose. Luckily i tightened them back in time.

Anyway what torque do you use to tighten your wheels for track use? I run on 19in wheels vmr v701 19".

BMW Manual says 87 +/- 7 ft/lb

I'm afraid that after 25 min my wheels are being unscrewed in rear. Do any of you use thread lock (blue) on wheel lugs? Is it even recommended?

Help!!! Got another track day coming up in 2 days for 2 days

Whats your thought on this?
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      09-25-2013, 04:42 PM   #2
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90 ft-lbs is fine, just make sure to re-torque them if they cool off (if you torqued them while hot.)

You don't need thread locker.
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      09-25-2013, 04:51 PM   #3
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+1 Agreed. No thread locker, OEM recommended torque is best.
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      09-25-2013, 04:52 PM   #4
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Ok thats what i thought but can a wheel unscrew on it's own when cornering hard after 30 min or only when it cools down, because my lug bolts could be unscrewed with a finger after the 4th session. I tightened to 100 ft/lbs but might be too tight now. So hell will go back to 90 i guess
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      09-25-2013, 11:40 PM   #5
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your bolts are probably stretched already. Get new ones. or maybe it's a good time to get studs. Couple things:
- no thread locker
- do not torque them when they are hot - stretches the bolts
- your torque settings are good
- every year or two, or when you see/experience any defective behavior, get new bolts. Those are maintenance items for a tracker. The heat cycles anneal the metal, making them weaker.
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      09-26-2013, 12:37 AM   #6
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Quote:
Originally Posted by will.c View Post
your bolts are probably stretched already. Get new ones. or maybe it's a good time to get studs. Couple things:
- no thread locker
- do not torque them when they are hot - stretches the bolts
- your torque settings are good
- every year or two, or when you see/experience any defective behavior, get new bolts. Those are maintenance items for a tracker. The heat cycles anneal the metal, making them weaker.
Ya i never torqued them when they were hot but will get new ones. Now are studs really better then bolts, stronger less stretching?
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      09-26-2013, 03:28 AM   #7
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Quote:
Originally Posted by labedra View Post
Ya i never torqued them when they were hot but will get new ones. Now are studs really better then bolts, stronger less stretching?
I understand your concern. Problems such as heat cycles, bolt fatigue, etc. are real problems, but the reality is those problems are concerns limited to race car parts or really old parts. Your relatively modern BMW can handle track days without the wheels, hubs, bolts coming close to failure limits. I've been on and off race tracks in a variety of cars for a number of years and have yet to see any issues with modern well-maintained car parts failing during a track day.

As for your last question of bolts vs lugs, there is very little difference between the two in strength and failure limit. Strength/stretch is negligible for similar materials. If there is any concern (minor), adding bolts/nuts adds additional parts to your wheel assembly, which means more parts to fail or lose. The major advantage of using bolts/nuts is that it can enable faster wheel changes, and make it easier to use different wheel sizes on extra long bolts without needing to have a separate set of lugs for each wheel set.

If this is still a concern, the best thing you can do to alleviate any possible failure is check the torque before each session. If they are in spec, leave them as is, if they are less, tighten them. After a few times of doing this you'll get a feel for how much they will "loosen”, which will be very little. If you're concerned about the lugs failing, replace them with OEM once a year as part of yearly maintenance for your track car.

I edited my post to include more info, and attach some reading materials. You'll find real world examples of bolt failure in these PDFs.

Last edited by RallyRcrr; 09-26-2013 at 04:01 AM.
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      10-30-2013, 09:42 AM   #8
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Quote:
Originally Posted by will.c View Post
...The heat cycles anneal the metal, making them weaker.
So wheel bolts are through-hardened? I would have guessed they were case hardened.
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      10-31-2013, 12:27 PM   #9
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Quote:
Originally Posted by NoTempoLimitN54 View Post
So wheel bolts are through-hardened? I would have guessed they were case hardened.
Well, I tried to look it up, but I couldn't find any. I'm not a materials guy either, but I kinda assumed through hardened med carb steel. Anyways, heat cycling would anneal the carbon casing as well, no?
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