CRex

The unfortunate incident in that other thread got me to think about the design of our street car centerlocks. I don't own a cup car myself, so this is just based off desktop research. For those in the know, please chime in and add your facts...

My premise is that PAG designed the 997.2 centerlocks as a compromise between aesthetics and serviceability by the masses. I observe two key design elements which differ from that of cup cars:

1. SPINDLE DESIGN
In most forms of high-end racing the spindle is threaded on the OUTSIDE such that the wheel nut mates with the spindle core.





The first pic is just for illustration; the second actually came from a GT3 Cup R. You can vaguely see the thread on the spindle, to the right of the safety hole.

Compare that with the street car design:



The threads are actually INSIDE the spindle. The wheel nut effectively mates with the inside of a hollow pipe. My potato logic says this just can't be as strong as biting on a solid spindle.

In hindsight, this design could be an accident waiting to happen. Improper torquing (both over and under), repeated stress cycles and the law of large numbers eventually produce a failure. That the thread housing got sheared clean off perhaps shouldn't be a surprise...



2. THREAD DIRECTION

Wheels are subject to the biggest torque on braking, which goes clockwise on the left and counter-clockwise on the right. For the same reason racecar wheelnuts are tightened that way. Our cars have nuts tightened clockwise on both sides. Why? Probably because PAG calculated that certain hare-brained mechanics might apply torque the wrong way and destroy the fragile spindle discussed in (1)...

OTHER DIFFERENCES

For safety, cup cars have a spring-loaded stud through the spindle. Without a wheel gun, this stud gets in the way of the wheel nut.

I hazard to guess that the safety lock doesn't matter as much. If the wheel nut is loose anyway, that little stud probably won't do anything to stop 1,300kgs of car on 1+ g's worth of lateral acceleration...

QUESTIONS / THOUGHTS

1. Did Porsche underestimate the "habitat" of the GT cars and how these CL's will be used? I can see the marketing angle for GTS'es and TT's which probably see one wheel change every two years. But for frequently tracked cars, this design seems underwhelming and weak compared to the cup assembly. At least to a layman's eyes...

2. Should the centerlocks and spindle assembly and be deemed a "consumable" item? Repeated torquing will introduce fatigue to the threaded areas which don't seem that strong to begin with. Do cup cars replace their wheel spindles from time to time??

ir_fuel

Do not forget that on the cup cars the CL system has to be replaced very often. It is not designed to last X years.

CRex

That answers one of my questions... the locks are likely a wear item, perhaps with a life tied to X number of wheel changes... something tells me the guys at PAG haven't figured that out yet, since that isn't mentioned anywhere...

mikymu

I much prefer my Cup CL design than street. It is 100X easier to get wheels on and off and much more robust as you have demonstrated. Why any car manufacturer even bother with CL for street use is beyond me

911rox

The centrelocks were designed this way to house a self locking mechanism which would be required for roadworthiness on the street. Cup cars use a pin to stop the bolt coming off... Track guys are religious about checking them before running. If you parked your car with cup car centrelocks on the street, someone pulled the pins off and your wheel came loose, Porsche would be liable... The street version was designed to address this.

Now time will tell if sufficient thought was put into the strength and reliability of the street system...

mdrums

All good questions and points. I believe that Porsche has a major issue brewing about the street center locks. Do you all think Porsche will just ignore this issue?

TRAKCAR

Yes, just like RMS and coolant hoses popping.
They are posting record profits and we just keep coming back for more :jumping:
I might go buy a Cayenne for the wifey too..

ChrisF

I know it's all about the profits, but seriously - how much would it cost to retrofit every CL car with an updated set of hubs vs. one really ugly judgement? Thinking as a bean counter, my guess is that somewhere deep in the bowels of PAG, they have already run the numbers. (cue ominous music

rlips

So True. But, it amazes me how people loose sight of human cost when they work for a large company. I can't believe that anyone at Porsche, face to face, would be callus enough to have no regard to creating widows or orphaning children, yet, as a corporate entity they have no issue with simply calculating the lower of the dollar costs and moving on.

Funny, as the folks who create our GT cars profess to be fellow enthusiasts, but will have no issue simply denying this exists and moving on.

Truly just, honorable people would admit this is a design failure, issue a recall and convert our cars to 5 lug wheels. The parts already exist (the 997.1 GT3). It would render any aftermarket wheels we purchased useless, but that would simply be the cost to us.

Now back to the real world............

jenk12m

in the world of porsche someone in there had to bring up these issues of the customers who change wheels very often with track use. although, im with peter that this will be ignored just like RMS and the coolant hoses popping off

mdrums

I'll say it again... Out of all the Porsche sold the people on this forum are a small minority that Porsche as a company could care less about. That pretty much goes for all car company's

911SLOW

To be fair, we have yet to see an RMS issue in the redesigned 2010 GT engines.

ChrisF

...until one of us gets hurt (god forbid).

outline

The cups from 2010 onwards no longer use the red sprung safety clip but have two small spring loaded tangs at the end of the central stud. When the nut goes on these pop back out and prevent it coming off.
To remove wheel these tangs are depressed and the nut unscrewed.

The rest of the system looks/functions exactly the same. The tangs are just where the hole for the spring clip is on the earlier cars.

I don't see any replacement timelines mentioned in my cup service books for the cup systems either. Just a check for wear and don't mix up the nuts or risk passing on thread issues to an ok spindle.

ATL Fahrer

To be fair to whom? Surely, not those 996 and 997.1 owners that have experienced catastrophic engine failure or had to purchase an aftermarket retrofit for several thousand dollars...

Wonder if Porsche will be as "fair" to us as they were to all those souls

I'm calm now