hmmmm.... i always found my wallet was the weakest point when it came to racing these cars!!! happy holidays everyone!!

 

I break two hubs on the same corner of my car in the exact same manner and cause a lot of damage in each incident. There is clearly a pattern in my case and I have it verified through analysis. FOR ME and the way I operate the car, the rear hubs have become a weak point. Whether you believe it or not is not my concern. Just because you have another opinion does not make it gospel. Do you even begin to grasp that?? Anyway, I post about my unfortunate experience advising people who track their cars heavily to check their hubs so the same doesn't happen to them. I'm sorry I didn't check with you to get you nod of approval before posting. Whether someone feels like the hubs could be a potential weak point for them based on what happened to me is up THEM to decide. I have a couple of pairs of heavy duty hubs made to preclude this from happening to me again. Since I have a spare set, I offer it up for sale and sell it. I'm not forcing any one to purchase anything. There is no embellishment, no fabrication, just the simple truth of what happened to me. If someone chooses to buy my spare set of hubs, which they did, IS CERTAINLY NO BUSINESS OF YOURS. There was no embellishment regarding the 300M hubs I put up for sale. I'm very proud how they turned out. For you to claim that I'm making false assertions to promote a sale (or "unload spare parts") is basically saying that I'm lying so that I can profiteer by this somehow. That's a personal attack and an insult. You my friend owe me an apology, plain and simple. And I'm saying this tactfully..

Honestly Dez, I respect what you've done and accomplished with your car but I just don't understand why you think that only YOU are always right and why you don't have the ability to concede that others may sometime have different experiences, results, conclusions, opinions, or even successes. The narrow mindedness is quite bewildering because I'm certainly not trying to steal your thunder so you have nothing to worry about there. Best of luck man and I'll leave it at that..

 

I don't owe you anything. There is no need for this to drag on. I have said my piece and explained it clearly with direct quotes. I will have to assume that someone researching this will see these posts and decide for themselves.



So Im going to change directions by now adding some useful information People tracking their cars heavily SHOULD worry about coolant lines, brake fluid pads and lines, rubber bushings (over time), drop links and toe locking plates. Pending history of the car they should have their hubs and all control arms inspected by a professional and considered for replacement. Even older hubs SHOULD be fine for many hard tracking sessions for years to come and new ones are good to go for a long time. They should probably try PSM off/disabled as it is actually safer than on in many cases. When lowering a 996 significantly they should install bump steer kits to lower the outboard toe pickup point. This is PARAMOUNT when running slicks.

Finally, in regards to the original topic, if the design of the re-re-engineered LCA's proves to be reliable, it does offer the advantage of no shims needed and a more fine tuned caster adjustment. I have had shims fall out before and a dynamic camber situation. If in fact they are as trustworthy, the concept is superior for adjustability. That's a big IF though. I trust what Tarrett says for the most part so those I would consider. The other brand needs a bit of seasoning for my comfort to supply a LCA on my car. But for street cars, I may have tried them.

 

As a final follow up on the hubs, below is a picture of the 997Cup hubs on the left which were all recalled and replaced with the new design 997Cup hubs on the right. The hubs on the left are the exact same casting as is used on the street 997 hubs which were on my car and which are a replacement for the 996 hubs which are no longer available. The main difference on the Cup vs. Street hub is that the Cup hub is not tapped for lug bolts but has wheel locating pins instead. People can draw their own conclusions, but I don't think it's rocket science as to why Porsche changed the design of the hubs which were shared with the street cars and switched to a much more robust variant for their race cars. Based on my failures, I have a hunch. Note as stated below that "Even the inner axle stub wall has been made thicker". This is precisely the area where I incurred failures on both of my hubs. Maybe it's coincidence or maybe this was deemed a weak spot of the hub. Who knows? The following below is a direct quote by BRR Racing regarding the hubs:

"We had our OEM street center lock failure in May 2012. We started this investigation in June 2012. We did our first project (on another customers cars) in late June, and all went well. We tested the car in early July. All went well. So, we embarked on doing the upgrade to this car as well, and ordered the same parts from Porsche Motorsport. When we got the new rear hub flanges, they were not the same as the ones we have as spares for our other Cup Cars, nor were they the same as the set we just installed. We thought Porsche Motorsport had sent us the WRONG units. We reviewed part numbers. Nope, these were the right ones. But, they were HUGELY different from the ones we had just installed, and had as spares. We asked what the deal was…..well, Porsche Motorsport had initiated a parts recall/replacement, and the old hubs were no longer available, only these new ones. Hmmm…..makes you wonder. The Cup Car hub has been around for a long time….why now, all of a sudden, does the design change. And, it is quite obvious what the design change is. The new units are MASSIVE compared to the old units. Here are some pics of the old vs the new Cup Car center lock rear hub flange. In every way the new unit is significantly different than the old unit….and it weighs a lot more as well. Even the inner axle stub wall has been made thicker. The wheel bearing is the same, and the outer pins are the same….the only piece that changed was the hub itself. Hmmm, do we smell an issue here? Well, on with the new, and out with the old."

[url=https://flic.kr/p/PGRN7m]

[url=https://flic.kr/p/Pcs3DJ]

[url=https://flic.kr/p/PGRN95]

 

They probably beefed them up because for a large number of people the street centerlocks have been a complete disaster with numerous failures. I have a couple of friends with 997 RS's that have had centerlock failures. Many 997 centerlock guys are switching to 5 lugs because of the inherent risks of failure. The frequent replacment intervals combined with high maintance, difficult operation and several warranty replacements that include lots of parts once on goes will get Porsche moving on a solution. As far as I know though the cup cars did not have any of the the same issues with hubs as the street cars did but maybe they found something in the centerlock design on the cups too, which will obviously need more support with one nut torqued to 400 lbs or so (I cant remember the exact number but its ridiculous). The whole street car centerlock idea has been a gimmick. There is no advantage for a street car. Only liability.

 

The street center locks share nothing with the Cup center locks but of course you know that. Thank you for clearing up the fact that the redesign was probably solely due to the failure street parts. Funny thing is that Porsche never put these heavy duty hub on the street cars where the center locks were failing. I suppose there is really no way to conceivably fathom that maybe, juuuust maybe, Porsche could have experienced some hub failures on their race cars and this precipitated their switch to the stronger parts? Hmm. I'm not going to go out on a limb and claim to know the answer. I'm certainly not knowledgeable enough to make a bold statement as to the true reason why the parts were beefed up but based on my experience I have my suspicions. Whatever the reason is, they went to stronger hubs just like I had my reasons for doing the same.

 

Porsche calls for the same service intervals if the centerlock cars are used on track so a logical assumption would be that the hubs are (or were at least) very similar. Looking at the old cup hub design it looks identical to the street hub for 997's so what exactly is not shared?

I have since read from a cup owner that the 997 centerlock hubs were a common failure as the street ones were. Notice people still are not having hub failures on 5 lugs so it seems to be an inherent flaw in the centerlock design. And Porsche supposedly replaced some of the failed street cars with beefier hubs to handle the huge torque numbers.

 

i think this is a failure related to the centerlock, not the hub...... the torque has nothing to do with the failure that John saw.

 

You are correct. It was the center locks that were failing on the street cars, not the hubs themselves. Those are two separate issues and taking about failure of the center lock mechanism only muddies the waters here. Porsche beefed up the hubs on the race cars for some reason. They beefed up both the center lock Cup hubs and also the 5 lug Grand Am Cup hubs. There is usually a reason why parts are strengthened. It's generally not done out of boredom or because the wanted to add unsprung mass. That was my point. Most intelligent people can arrive at a similar conclusion. I beefed up mine because of the failures I had. If I didn't have failures, I would have had no reason to go through the effort and expenditure of having the 300M hubs made.

To answer your question, both the metallurgist and the engineer at DSS told us that torque is a contributing factor in the failures among the others I listed earlier. I have no reason to doubt doubt those that certainly know more about metal fatigue than I do. The hubs do flex minutely both radially and laterally which eventually results in metal fatigue. It certainly makes sense and perhaps that is why Porsche went with such a heavy circular design without the cut outs in order to minimize any flex. Just speculation on my part.

 

There is an NHTSA report on Porsche recall of the hubs around 2010. Porsche claimed the hubs were the problem. But it does seem as though either a defect in the hub itself, or somehow it relates to the locking mechanism, or them possibly relating the entire connection as a hub. The seeming connecting point to the failures has been deemed the hubs. And seems to be concurrent with the centerlocks. So clearly Porsche had some issues with the centerlock hubs themselves. But there has never been a recall on any hubs related to 5 lug wheels. That was my point. Just eyeballing the old Cup hubs, they look darn near identical to the hubs on our street cars which says a lot for the hubs on our cars. Hubs should be a wear item on a race car on slicks. As mentioned before, but not on street cars and DOT tires as is evident by the lack of documented failures.


You can find it here.

http://www.excellence-mag.com/of-not...s#.WECQdPkrLIU

 

The GT3 Street Center locks actually thread on to the hubs. The cup car center locks are threaded onto it's tension bolt that threads on to the driveshaft. Even if the cup cars had center lock failures it would not affect the hubs. Not even close between the two for comparison. The Center Lock street hubs are quite frail Not even close to motorsport grade. The 996 center locks are essentially the same hubs as the streetcar, however are machined for locking pins and center lock centering washers. You could quite easily modify a street hub on the 996 series or the lug type hubs to center lock with mild amount of machining.

 

I dont profess to know the inner workings of the various hub assemblies. I dont even know why we are talking about cup cars anyways. This is not a cup car, not even a race car, not likely even to be the same causality of the failure considering cup cars dont have much torque at all relativel speaking. There are no slicks, there are is no racing and there are a mountain of other TT's being tracked on original hubs and slicks with lots of hp.

Im changing my hubs soon as recommended by my shop, but I dare you find some that have gotten more work than mine.

 

Excellent explanation. Thank you. As I posted above I knew the Cup center lock was totally different from the street but I was not familiar at all with the street unit and its workings. As I said hub and center lock issues are two different things.

When I posted the thread on Rennlist a few years ago about my initial failure and the subsequent failure, many people chimed in thanking me for bringing it up. Two people reported a hub failure they experienced including one on a 996 and several others stated that they change out hubs and bearings proactively. Mooty, who is one of the most respected track rats in the GT3 community, says he swaps out wheel bearings every 25 track days and changes out hubs and wheel studs every 50 track days or 2 years. This is very much in line with what I suggested here even though I have not had any issues with bearings and would personally be ok with 50 days on those also. Interestingly, unlike our resident 6spd Expert here, not a single person on rennlist accused me of fear mongering or exaggerating in order to "unload spare parts".

Bottom line is, based on what happened to me and the rest of all this minushia, it is up to individual people to decide based on their use and their level of risk tolerance what if any replacement of hubs or any other suspension components is warranted. I can simply provide a guideline and recommendation but the decision lies with the end user.

Have fun gents and be careful out there as this is a dangerous hobby which can hurt you or worse.. cheers!

 

the new 997 Cup hubs might be a nice option...any ballpark on pricing? drive pins appear to be drilled in same location as standard bolt pattern...maybe can use press-in studs?...

 

You would have to drill to larger hole size and tap. Piece of cake. The drive pin bolts are pretty small size.