powdrhound

I posted this on the other forum but it's more useful here as this is more of a track hound forum. I had a left rear wheel hub snap on me after exiting a 1.3G right hand turn at the track a couple of weeks ago. No warning. If you heavily track your car I'd consider these a wear item and proactively replace them at some point... Unfortunately it's almost impossible to visually check something like this for fatigue or cracking so the only option is a proactive replacement. I've never given these components much thought but as these cars get older, parts fatigue is starting to become a factor. It could have been ugly. (Yes, we did check the big central drive shaft nut and it was still fully torqued after the incident). The 997GT3 hubs have been redesigned and are thicker that the 996 versions.



[url=https://flic.kr/p/oBB39v]

The brains behind my local race shop came up with a plan to upgrade the rear suspension with much beefier race components. Well, the car is back together. We put in new uprights, new bearings, and new hubs. We put in 997GT3 hubs which are indeed thicker than the original 996 hubs. While at it, we swapped in all new wheel studs replacing the ones that have been in for the last 3 years. Additionally, we ended up installing PMNA 997RSR 2 piece lower control arms. These are really slick as they have an inner monoball along with solid adjustable thrust arm bushings and a super beefy replaceable outer monoball joint. Since this was one of those "while in there" moments, we also ended up putting in PMNA 997Cup toe arms. These are really nice as they employ a "pinch" collar on both ends to lock in the adjustments. This makes alignments a breeze compared to the jam nut arrangement. Finally, we put in new 997GT3 thrust arms and new 996TT driveshafts. The last piece of the puzzle was the install of 997.2GT3RS brake cooling ducts. This version is much more efficient compared to the old 6GT2 units as it get much more air to the rotor along it's full annulus. All in all, this was a bit of an unexpected project but I am happy to know I have a much stronger set up going forward and can feel confident pushing the car hard again. Just wanna say that this upgrade would not have been possible without the assistance of my local "skunk works" race shop owner/friend that suggested and sourced all the necessary parts for this project.

New hubs with new studs. Note how the GT2 heat shields had to be trimmed to clear the RS air duct
[url=https://flic.kr/p/oMGZYX]


997RSR LCA. Note the outer monoball and the RS air duct.
[url=https://flic.kr/p/p4vRKB]


997GT3 thrust arm air guides. Note the belly pan NACA duct exit in the wheel well liner and the 997Cup caliper studs
[url=https://flic.kr/p/p5c3WM]


Rear view of the RS brake ducts and the 997Cup toe arms
[url=https://flic.kr/p/oMH2A5]


Close up of the pinch bolts on the 997Cup toe arm. Note the use of a double jam nut arrangement instead of the OEM single nut.
[url=https://flic.kr/p/oJvntn]


Close up of RSR monoball
[url=https://flic.kr/p/oYXDv5]

mooty

great post and as I said long ago, hub, studs and upright are all time out items, and ppl thought I was crazy.

lfish

Mooty, I don't believe anyone ever questions your knowledge of GT3s. However I did question your sanity when you stated that AAPL was just a fruit

996FLT6

Has neone had a hub failure with regular lugnuts? Just curious. Mike

996FLT6

Only reason I'm asking is definitely going studs is its longer and because of that swapping rims incur way more fulcrum weight and say if for some reason 2 of the five studs get taxed ie possibly incur slight fractures they snap. Now u have only 3 studs plus hub supporting wheel. And u know certain types of studs do fail. I've ran my lugnutted 6 for one session never knowing the locked ones weren't titened and those fell off while tracking 30 mins and did not notice a thing til I came back other than coming back to paddock checking pressures and noticing all 4 lock luck nuts were gone. So that's why I ask neone with lugnuts had a total hub break off and everything was trq to spec? Mike

powdrhound

I'm using German made studs. I've never had a stud fail but I religiously check wheel torque after each run. I torque to 118ft/lb. I believe studs fail due to under torquing allowing the studs to flex which eventually leads to failure. I had close to 70 track days on the set I just replaced.

996FLT6

Just saying maybe with a sharpie number the studs 1-5 and mount them equal ie if 1/2 stud is on top rotate to opposite side. Weight of wheel on same stud can incur slight fractures. Anyway neone had same issue with lugnuts? Mike

996FLT6

Also what's the advantage of studs other than ease of wheel changes and flexibility with rim offsets? Mike

powdrhound

There is a bit of a misconception here. Wheel studs or bolts do not support the wheel by themselves. The load of the wheel is primarily supported by the "lip" on the hub, not solely the studs or bolts themselves. Now if your wheel nuts/lugs are loose than a load will be placed on them, they will flex, and eventually fracture.
I'm not understanding how the stress on a hub would be different with studs or lug bolts. If you look at where the hub failed, it was nowhere near the wheel studs but rather at the base of the hub.

996FLT6

With studs sticking out as far as as they do vs lugnuts. Can u bend them easier vs lugnuts. I bet u with my weight only foot on on of the studs I can bend it. Say I stud is as short as a lugnut- no way u can bend it. So u saying that hub is the only part is supporting wheel and not the 5 studs or lugnuts. So u saying I could just have 2 studs or lugnuts on and it wouldn't matter vs 5 lugnuts or studs? Im just saying its n

996FLT6

U need both 5 bolts and the hub to support the wheel. All u need is to bend two studs it'll fracture with repeated use. Mike

cfjan

Do you need the 997 uprights to run the 997 hubs? Or you can use the thicker hubs on the stock uprights?!

powdrhound

You can use the stock 996GT2/3 uprights with the 997 hubs.

996FLT6

How many miles did original hub last? Question is what would be recommended as miles due to wear if track alot? Also being 997 hubs more robust what is replacement interval for that as well. Mike

cfjan

What's the reason for you to replace the uprights then? Better geometry?