911mhawk

How long do you run your studs and nuts before putting on a fresh set?

I put on all new hubs and bearings but reused the same studs I've had for 2 years and was just thinking...

T10Chris

2 years for street/track cars is what Tarett recommends.

http://www.tarett.com/images/STUDS.pdf

997rs4.0

Just changed mine last week. IMO 2-3 years is probably ok for a DE car without slicks.

mmuller

I used to time them out every year. Last year I broke 6 in 3 separate incidents, almost crashing the car each time. I took them all out and threw them away. Never saw anyone break a wheel bolt.

Yes its more of a hassle, but crashing the car would be more of a hassle.

993GT

I'm also in the wheel BOLT camp...

Jferrante

yikes - i broke one and didnt know about it until i went to change the wheel. Did you break more than 2 on a wheel?
Also saw your car at Aspen - went up there last week - ready for spring!

powdrhound

Torque your wheels to 118 ft.lbs. Your stud breakage woes will go away... 96 is a carry over from the old air cooled days when Porsche used aluminum lug nuts and seems too low allowing for some flexing of the studs eventually leading to their failure (sort of like flexing a paperclip back and forth). In 6 years of heavily tracking my car and torquing to 118 I've never had a stud failure. I only use German H&R studs... Lot of the fancy "Nascar" type studs have dubious origins. Know exactly what you are putting on your car..

To be clear, I torque the stud in to the hub at 32 ft.lbs and wheel at 118. Incidentally 160NM (118 ft.lbs) is what Porsche switched to on 991 and later cars using the same 14x1.5mm lug bolt size.

mmuller

Not true. I have been torqueing to 118 since I started this hobby. I have tried many brands of studs and the last ones I tried did last longer, but still broke. I have even tried the reputable ones that are made for the IMSA Porsche teams, still broke those. The last one had 2 studs break at once going over the top at Palmer. Every time it just pulls the stud apart

Since I went back to bolts, torqued to the same amount as the studs, guess what, no breaks.

And yes, my car is heavily tracked. Its on track 50+ days a year.

mmuller

I had one day that 3 broke at NJMP Lightning, all at the same time. The at Palmer, I had 2 break at the same time.

That's when I said enough is enough, I won't get lucky again.

Everytime, the nut and broken stud stayed in the wheel until the car came to a stop. The last time I stopped and the two studs passed me and went 20 ft up the track!

AudiOn19s

no studs for me either. I never even put them on the GT3 after seeing soo many reports of failures here.

I did finally replace my wheel bolts last year just for piece of mind since they were the original bolts from the car.

powdrhound

All else being equal, if you're breaking studs but not OEM bolts, that would CLEARLY point to a weakness in the type of studs you were using. No other conclusion can be reasonably reached. Have you had a metallurgist examine one of your broken studs to give you an assessment of the root cause? You can learn a lot there as it will tell you the quality and harness of the material used among other things. Every one of our spec Boxsters even those set up and used in 8/12/24hr endurance racing use H&R studs and none have seen a stud failure over the last 4 years of racing. Plenty of blown up motors and other carnage but no stud failures. Try the H&Rs, you might be pleasantly surprised. No affiliation, just sharing what has worked for us over the years..

mmuller

I have literally tried all the studs on the market, but admit to not trying the H&R and at this point, not willing to risk it with the car. The bolts work, don't break and I can drive with confidence.

I use studs on my SPB however. Never had one break on it either. And like you, plenty of other carnage, but no broken wheel bolts. In fact, last year at Sebring the car got hit right on the driver side rear wheel. Bent over all the wheel studs but none of them broke (which I fully expected). I felt so good about those studs I tried the same type in the GT3. Second event, they broke.

I have not had them inspected, but its a moot point now. This is picture of what the end grain looked like on one of the last ones that broke. It had about 10 hours on it when this happened.

powdrhound

Interesting. One other item that comes to mind are the wheels. What kind are us using on the GT3? The reason I ask it that if the hub or lug bore was off even minutely it could be placing undue stress on the studs themselves quickly leading to failure. No matter what though, if you are breaking studs and not bolts, it is clearly a material issue with the studs and not the wheels.

Unfortunately I have no point of reference as I have never used anything else besides H&R studs. I will tell you though that over the last 6 years I've not had a single failure of a stud (knock on wood) but I have snapped numerous hubs including a gearbox output shaft as if it was a twig. This is on a 996 with a Cup suspension set putting 600hp to the rear wheels and running at a much faster pace than a 6Gt3. All of our local GT3 guys are running the H&Rs also and not a single failure over the last couple of years.

Anyway, things like this always intrigue me as there is always a reason and a solution to a problem.

Regarding the pic of the stud you posted above, I bet a metallurgist would be able to give you a good idea of what is causing the failure based on the grain structure visible.

mmuller

I have two sets of OZ wheels and a set of CCW's. I have broken studs using either wheels.

My suspension is all monoballed (RSS Tarmac), solid strut tops, Ohlin's TTX 3 way's with 700 and 900 springs. Its still a 3.6, but puts down a little over 400hp at the rear wheels based on dyno results. Interestingly, it runs at a pace that is faster than any of the GT2's or Turbo's it find's and regularly runs away from a 700hp widebody 996GT2 that is part of our region.

I agree, its a material issue and also likely could be influenced by manufacturing techniques (rolled or cut threads).

powdrhound

That just proves you're a much faster driver than they are. I'm slow on the other hand and have to cheat to keep up by using a faster car.

Meant to ask earlier, were most/all the studs you broke on the rear axle or also the front? Obviously the rear sees the most load.