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      02-05-2013, 07:59 PM   #1
paradocs98
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Drives: 2014 991 Carrera S
Join Date: May 2009
Location: NY

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More info on wheel studs

I'm getting ready to order a replacement set of wheel studs for the car in anticipation of trackday season approaching. I've been doing a lot of reading about the stud kits from the various vendors, and have narrowed my choice down to either another Turner Motorsport set or the Bimmerworld premium race studs.

The Turner studs on my car now are my second set and have been of good quality, but I had an issue with a few of them loosening from the wheel hub. See thread:
http://www.m3post.com/forums/showthread.php?t=743275

I followed the Turner instructions for installation--applying the included red Loctite to the ends of the studs and torquing them to 16 ft-lbs into the wheel hubs. My first set didn't seem to have a problem with loosening or backing out, so I was surprised to find my second set having this issue. After doing some reading, I think I may have an answer: apparently if your wheel hub threads are not perfectly clean when installing the new studs, the studs can fail to make a perfect seat, and then loosen over time. This is made worse by galling of the lugnuts on the studs. If the nuts become somewhat adhered to the studs due to corrosion, etc., they can end up unscrewing the studs from the hubs when you loosen the lugnuts. The galled nuts effectively "double-nut" the studs out of the hubs to a certain degree. This is made worse by the use of an impact wrench.

Some people recommend a tiny bit of anti-sieze on the stud/nut threads to prevent this galling phenomenon, but I'm wary of that--I would be concerned that the lugnuts couldn't be properly torqued if the studs were coated with antisieze.

The sensible recommendation seems to be to thoroughly clean out the wheel hub threads prior to installing a new set of studs. This may be why my first set of TMS studs didn't loosen, whereas a few studs in my second set did. My hub threads were probably much cleaner during the first installation, so the studs got a better seat and Loctite seal. For this next installation I'll use a clean lugbolt as a thread chaser to clean out the hub threads, and then blast the hubs with compressed air. Hope that does the trick.

There's been further confusion about proper torque values for installation of the studs into the wheel hubs. TMS very clearly specifies 16 ft-lbs, whereas Bimmerworld recommends a higher value for their kit. There is widely varying opinion on the message boards as to what the Bimmerworld torque value should be. The studs from both TMS and BW are likely sourced from the same high-quality supplier, based on the descriptions on their websites. TMS and BW say the same thing, practically verbatim: "They're made from heat-treated 190,000 PSI chromoly steel, shot-peened and double magnaflux inspection." Speculation is that ARP is the supplier.

One significant difference between the two is that the Bimmerworld studs incorporate a "larger diameter shoulder for the stud to bottom out on, instead of allowing the threaded section to bottom in the sharp threads" of the wheel hub. This shoulder sits at the base of the non-threaded portion of the stud, and theoretically helps prevent stress risers or cracks from forming in the stud when the non-threaded portion digs into the wheel hub threads. This probably helps explain why Bimmerworld recommends a higher torque value for installation of their studs into the hubs.

Because of the disagreement on the various forums about the true torque value for the BW studs, I contacted James Clay from Bimmerworld. Good guy--very friendly and got back to me the same day.

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My query to him:

Hi James--

I'm potentially interested in your premium race bulletnose wheel studs for my E90 M3 that sees 10-12 trackdays per year. I don't see any instructions on your website, however, regarding installation. Obviously they need to be double-nutted on given that there is no hex-key receptacle on their ends, but what torque value should they be set to? I've read conflicting info on various forums--some people torque your studs down to 80 ft-lbs, while others set them at around 20 ft-lbs given that they come already coated with dry threadlocker. The 80 ft-lb guys say that a lesser setting will allow the studs to come loose, while the 20 ft-lb guys say that torquing them to a high value like 80 will cause cracking and failure. Also, I'm curious as to how you would go about torquing the stud to 80 ft-lb while trying to hold the rotor still with your other hand.

Could you help clear up the confusion?

Thanks a lot for your help!


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And his reply:

That is the great debate. I know that we use the applied locker, we torque to 80, we don't have broken studs, and we don't have studs back out. I know that when we did them to 20, even with a clean hole and various lockers, we had studs loosen up. My official statement is that 80 is correct, as close as you can get to that is the best, and I would like to see them over 50.

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Hope this rambling post helps clear up some of the confusion out there.
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