[Pat]

I was talking with a BRZ friend of mine recently that is a knowledgeable, experienced driver. He pays close attention to vehicle maintenance including wheel lug torque specs. He recently had a couple OEM wheels come loose on the track. Fortunately he was able to get the car slowed down in time to keep them from coming off. His wheels were damaged, so he spoke with his dealership about it. After giving him a hard time, he was finally able to speak with the field engineer about this issue. The engineer said the OEM studs and lug nuts are only designed to withstand 75 to 80 changes over the life of the vehicle. My friend actually had the failed studs tested and said the metallurgy is terrible. Here is an email I got from him about it:

re : the Subie engineer and my wheel studs and lug nuts, he was a pretty cagey dude. he would put nothing in writing for me despite several requests. Clearly, the design life of parts is not something they want to discuss openly. I felt pretty lucky that they replaced both ruined wheels as a "courtesy" rather than under warranty. He made it very clear however that our cars "arent designed for track use ". and "this car isnt a Porsche". of course I said they "why isnt all that in the owners manual ?" .
bottom line is the "design life" of the lug nuts and studs is 75-80 wheel changes, on average, in the lifetime of the car. "Kmart" parts used in quite a few places on a $25K car, I suspect.
In order for you to avoid my issues, I strongly recommend you go to ARP studs, kit # 100-7727 for FRS or BRZ. their tensile strength exceeds grade 10.9 steel so they are the best you can get.
For your information, I researched the stock studs and lug nuts. they are made from < grade 8.8 carbon steel. in short that means they are el-cheapo Kmart parts.
grade 10.9 alloy steel is generally the best steel other than "aircraft quality" . ARP has a tensile strength rating system and their's are better than grade 10.9.

Be careful out there, kids!