CRex

RL'ers tracking centerlock cars, take heed:

Facts:

• 2011 GT3RS, mainly tracked
• Driven to track on street tires and switched out to track wheels in the pits
• 30-35 wheel changes in the past 1.5 years, mostly from preventative maintenance and trackside switching as described above
• Car has only been paired with two sets of wheels ever: OEM and Champion RS20s
• Tire pairings: numerous sets of Hoosier R6s, occasionally MPSCs and Trofeos
• Wheel changes performed as per Porsche bulletin--wheels torqued off the ground to 450lbft; contact areas greased with optimoly
• Center splines always in the "secured" position and visually checked by me before each track session

Observations:

• Centerlock nuts typically get tighter over time as the optimoly dries up from heat and binds--logical and no surprise
• Breakaway torque should henceforth exceed 450lbft, though not by much
• Earlier this year I began noticing that the RR (i.e. the passenger side rear for LHD vehicles) CL nut is noticeably easier to loosen than the others
• After a two-day track session this weekend (15 heat cycles and 95 laps of a 4.3km course) the RR nut took less than 300lbft to remove even though it was torqued to 450lbft just 48 hours ago using the same torque wrench
• The five red alignment pins on the RR hub show superficial scratches consistent with the scratches on the 3 other hubs, but MORE SO than any other. Keyword here is more, but not necessarily deeper, and nothing similar to the "problem" pictures in the official bulletin posted here last week
• No unusual signs of wear on the hub, rotor bell surface or wheel mating surface as per said bulletin

Immediate Thoughts:

• Even with the center splines fully engaged, the nut can still turn approx. 20-30 degrees by design
• The RR CL nut appears to have gradually loosened itself from repeated stress on track
• Whether the center spline effectively stopped the CL from further loosening will never be known; wheel may have been taken off in time before further stress was levied on the spline mechanism

Car is going into the dealership to have all hubs inspected. Will try to push this through as a warranty issue but I have a feeling it will be denied given track use. Regardless of the claim, I'll have the RR hub assembly replaced even if out-of-pocket.

Just when you thought following Porsche instructions to the tee would prevent problems with these fecking CL's...

p.s. can anyone with the official bulletin quoting the 296lbft breakaway threshold please email me a copy so I can confront the dealership with the technical facts? I will obviously not compromise the source in any way...

911rox

Wow! Hmmmmm... not good at all Crex...

Can I ask how you measure the breakaway torque? Is there a specific tool that does this? I currently use a big *** breaker with a 5' pipe over it and it takes a sh!tload of effort to crack those suckers....


Ps... Refer page 1...

https://rennlist.com/forums/attachme...wheel-lock.pdf

Veloce Raptor

5 lug conversion FTW...

FFaust

Interesting.

Quadcammer

get rid of them.

mooty

thx for the note.
I'll be quadruple carful now.

mdrums

Soon a 997.1 GT3 will have better resale value than the 997.2 GT3!

deputydog95

I would be okay with that.

savyboy

Peak reading on the torque wrench as you break the nut loose Chris. If you are using the breaker bar you will have to guess if you exerted more than 296ftlbs to break the nut loose.

CRex

It's pretty simple... just use your torque wrench, set it to 300lbft and flick the ratchet from CW to CCW. Gently apply force to the wrench if the nut starts unwinding before the torque wrench clicks you know the breakaway's at less than the threshold you've set...

p.s. thanks for pointing out the technical reference!!

Veloce Raptor

FYI: never a good idea to use a torque wrench as a breaker bar...

911rox

Hey Pete, my torque wrench is one of those where you twist the handle to dial up the required torque so it desn't display peak reading... Would I dial up say 500 nm and see if the nut cracks before the TW clicks?

911rox

Ok, got it now fellas... Thanx!

mdrums

Start with a lower setting like 300ft lbs and see if the wrench clicks and work up till it doesn't click anymore and finally loosens the CL nut. Then you'll have a good idea if the CL nuts are holding torque.

CRex

Agree, the intention was never to "break" the CL using a torque wrench. I usually untorque using only the first two segments (i.e. without the last torque meter part) knowing it should take considerable force (matter of simple physics--T=N*m). I became suspicious after discovering the little effort required of the RR nut and that to start measuring its breakaway torque...