Well first, let me state the obvious. None of our cars have enough DF or are light enough to make use of 670 wheel torque. So putting that much power on a car that heavy is asking for things to break. You aren't making the car any faster unless you are running at Road America or Cota and even then only minutely so, because the increased straight line speed without reduced weight or high levels of DF isn't helping in braking zones or cornering. All it has done is make the braking zone significantly longer and putting power down on exit much harder.

#2 A real cup car is much faster than our cars as well. Especially when our cars are on DOT's, so let's not throw that term around loosely. Your average joe showing up in a Cup car is 5-15 seconds off the pace of even cup challenge driver let alone a pro. My car has the fastest relative lap times around here and I'm still a 1-4 seconds off pro's.



Brakes? Not really sure how you are relating that to the hub failure. Not to mention, the front brakes do almost all of the work. So that wouldn't exactly be applicable to a rear hub failure.

 

Well to assume that the rear brakes do no create heat that transfers to the hubs would be silly. If heat was not an issue with the rear brakes, ducts would not be a factory available option. And while the fronts do a majority of the braking, the rears take almost all of the torque(in RWD configuration) and lateral loading. Next track session you should take an IR temp sensor reading of you brake hats immediately afterwards. Heat cycles, torque and side loading are all compounding factors to stress induced failures. And if it wasn't a known issue, Porsche wouldn't have beefed up the rear hubs on the 997 GT cars. I do agree that his power levels probably don't help the issue.

 

We may be able to attribute the first failure to that because they were old and had lots of track miles on them. Im questioning them failing almost instantly as was the case with his replacements. I just don't think a brand new one would spin apart that quickly and easily. His second set had not had time to really sustain many heat cycles.

 

Yes. Thanks. As you say, obvious.
I was looking for answers as to why the hubs COULD BE breaking, heavy. Not speaks against them breaking.

But I am sorry, I did not include you in the list of forum members running their cars in a similar fashion without these issues. I don't know why you didn't come to mind first - maybe because you were part of the conversation here. But this just goes to prove my biggest argument against the hubs being too weak.

 

You are correct. Porsche Motorsport also completely redesigned the hubs on 997Cups several years ago from the design that was shared with the street cars. The new design is much beefier. They did not do this out of fun but I would imagine out of necessity. Yes, we considered changing my car over to the new 997cup center lock hubs but I did not want to do that as it would require a ton of new part$ including wheels and I already had $15K worth of wheels on hand. Manufacturing a pair of 300M hubs was the cost effective way to go in my case since you don't need to worry about the fronts as there relatively minuscule stress imparted on those.

This thread is getting silly. I wouldn't waste your time trying to convince someone of your point. Some people have their mind made up and will dispute the obvious fact that is is possible to operate the car is such a fashion as to overstress certain components even in the face of what metallurgist and others have pointed to as the cause. Gee, must not be possible since other people have not had this problem. Must be just a fantastic coincidence that the same parts have failed on the most stressed corner of the car and those same parts have failed in the exact same fashion and in the exact same area at which contain the highest stress riser by design. I could go into an explanation why that particular area contains the highest stress riser but I think I'd be wasting my time. What I will say is that the design of the axle splines not engaging fully all the way to the end of the splines in the hub is a contributing factor as it allows a minute amount of twist (flex) to be transferred into the hub component. This minute twist eventually contributes to the weakening of the metal. Our metallurgy guys have stated that this is likely done so as to soften the shock loads going to the axles and this was confirmed by the DSS axle guys when I inquired about having them produce some axles with longer splines. They advised against doing this as it would in turn drastically reduce the life of the axles. You beef up one component and the downstream one will fail. As I said before, the 2nd hub I installed was shortly after having my engine rebuilt and I got 45.8 track hours and 110 session on it, so no, it did not break right away. Nuff said...

Regarding brakes, I'm running the 997GT3/Cup rear calipers which have 50% more piston area that the stock 6TT/GT brakes. By comparison, the stock 996TT/GT rear brakes are significantly underutilized. The Cup ABS also has a much higher threshold limit which shifts braking action further rear. When I swapped from the street ABS to the Cup ABS I had to switch to a lower friction pad in the rear as the rear bias was suddenly too great. It was really a significant difference. While the braking action with the Cup ABS is phenomenal, I am eating through rotors at a faster rate than before. Even with all the 997Cup rear cooling ducts the rear brakes typically run 60-80F hotter that the fronts which run relatively cool as they are cooled by a ton of air from the front ducts and from the radiator air that is channeled over the front rotors. Yes, the front brakes still provide more braking action than the rears but the rear brakes do run significantly hotter in my application as they are much more effective. I have this verified as I log rotor temps on a regular basis. If the rear rotor hat is hotter than the front rotors hat, it stands to reason that the rear hub is hotter also. Having said all that, with all the cooling ducts on my car, my brakes overall do not run any hotter than those on other GT3s that I have measured at the track so I don't see heat as a main contributing factor in the equation.

Yes, I have Motec data showing both a reduction of lap time after having my engine rebuilt as a 3.8 thus producing significantly more torque at a lower rpm than as a 3.6. While peak torque is not hugely different at 673 v. 631, the 3.8 produces 170ft.lbs more than the 3.6 at 4000rpm. I also have data showing a further reduction of lap time running wider tires. I won't go into it here as it's pointless to try to prove the obvious.

How hard you run your car has an implication how hard you're on equipment. One of the guys I run with frequently is a accomplished driver who finished #3 in PCA GTA2 2016, not exactly slow. He runs a modified 997.2 Cup with an RSR engine/gearbox. On NT01s I'm about 4-5 seconds off his pace on a 1:50min 2.55mile lap. When he ran a stock GTC5 7.2Cup the difference was about 2-3seconds. 7.1 Cup is about a second. Gap narrow significantly when the Cup is not on stickers... Yes, I push the car pretty hard.

In summary, high engine torque, high lateral loads, sticky tires, very stiff 1500# spring rates, monoball suspension throughout with zero cushioning, heat cycles, and hard use over many hours and cycles acting on the most highly loaded corner of the car will eventually lead to a failure of a hub. This is the conclusion of having spoken to many guys smarter than I am when in comes to this stuff and I have no reason to doubt them. If some guys don't buy this, oh well...

 

No need for everyone to get salty. Forgive me if I'm not one to believe it because it was posted on 6speed. I'm only putting the facts together to draw a reasonable conclusion.

My reasonable conclusion is that you aren't putting enough power through NT-01's to break hubs that quickly. 1500 lbs springs are too heavy for NT-01's, you will have less grip not more. Cup cars run those rates on full slicks that hold much higher g's. Not to mention your home track doesn't really even have any big elevation changes so no real compression forces to exponentially raise the stress on suspension components. Not to mention you broke a beefier 997 hub in record time quicker than you broke the 996 hub. And you ran the 996 hubs with the Kumho's quite a bit and they were 12 years old. I'm sorry, but that just doesn't add up. It seems like something else it wrong with this equation. It doesn't make sense that this is the only documented case of hubs being blown this quickly, on not that sticky tires, on overly heavy springs. I'm sorry but it just doesn't. It certainly was not heat stress/cycles on the 997 Hubs that broke quickly was it? That being said, it's how much sense does it make to keep trying to run that power if you have things exploding left and right because of it? You'd rather spend 4k on specially designed hubs than turn the boost down a tad? That would seem like the logical thing to do if you thought it was the hp/torque. I also don't buy that the car gained much time BECAUSE OF a gain in torque from 630-670 wheel torque. You may have as a driver, but the facts don't lie, throwing more hp/torque at an already high hp machine without other mods isn't increasing the capabilities by much if at all. Law of diminishing returns. And on track you shouldn't be at 4k RPM much at all especially if you have a higher redline. If you are at 4k or less it's exiting a very slow turn, and you are not flat footed, not on NT-01's and 1500 lb springs. So you aren't even using all of the torque you have available at that moment. If you are, you are in the wrong gear.

That being said, do what you want, but trying to sell these hubs off under the pretense that "OEMs are an annual replacement for those tracking hard averaging 20-25 days per year" is nonsense. That is a fact.

 

Wow. I'm out.

 

Yikes!! This is blossoming into full on ****show!

 

Nobody is salty but sometimes it seems like you would argue over the color of the sky just so you would have the last word.

First of all, I'm not selling anything nor do I have any hubs to sell. I had the hubs made for my own use to solve a particular problem. If you think it's idiotic for me to suggest that people keep an eye on key suspension components whose failure can cause a lot of damage and to consider proactively changing it out in light of how cheap the hub is, well, I won't comment on that one. I'm just sharing my experience so perhaps someone can a avoid the same fate. I'm not telling people what to do. If you think because you read about it on 6spd it's BS or made up than that's your prerogative. If you think all the people that looked at the failure of these parts are wrong, well, you are without a doubt smarter than everyone else. Perhaps you can shed some light on why Porsche totally redesigned and beefed up the hubs on the Cup cars? Maybe for fun, maybe they were bored? Any ideas? Has it occurred to you that this may not be an isolated failure but that it has happened to others, the difference being that they may not have gone and posted about it on 6sp or rennlist? Lots of guys stay off the forums you know. Maybe you do, but I certainly don't get a memo every time someone breaks something on their car.

Secondly, thank you for all your insight on the correct spring rates, or the incorrect spring rates rather. All the data we have on the various spring rate combinations we have tried must be wrong. Or perhaps we just don't know how to interpret data and look at lap times? What were we thinking wasting our time analyzing numbers when we could have simply emailed you for your advice? My hats off to you my friend, you are wise. No disrespect, but have you ACTUALLY tried various spring rates in 100lb increments up to and including Cup rates using motorsport quality shocks on your car and compared lap data so that you could intelligently speak about the topic? Is your opinion solely based on what you read on the internet or heard through the grapevine? My guess is the latter. Have you had failed hubs and had them analyzed so that you could offer an intelligent analysis to the root cause of the problem? The answer is no. The fact that you have not heard of this happening to someone else doesn't mean anything. I certainly won't go out and advise people on something I have no 1st hand knowledge of. Your set up may work for you and I'm not gonna go out of my way to discredit it. Seriously, not trying to be a smart *** but you seem to an answer for everything.

I'm done with this..

 

You were selling another set of the hubs in the post I quoted. Do I need to re-quote it for you?


Its irresponsible for you to post false information regarding the hubs as a weak spot being a track veteran with so many newcomers to the marquee who may look here for guidance. I usually let you post this misinformation without response, but decided not to this time.


To answer your question though, no I haven't run 1500 lb springs on my car, but have driven my friends 996 TT with something like 1200 or 1300 on 3 way Motons and coincidentally NT01's. Car would not set and never felt planted, his words. In fact I was driving it for that reason, he wanted me to feel what he was. It was very sketchy in low speed turns until it sent him off track. Ya think? Im all for trying different things but there is a reason no one runs on those heavy springs because NT01 dont produce enough grip to compress them and make them take a set to give you confidence to floor it on exit. I couldn't get my car to set early enough on A6's with 1000 lbs rear springs at full soft.

 

Heavychevy, i always respect both what you and pwdrhound share as coming from a place of experience and mostly not vendor biased. And I think I can appreciate what you are saying as coming from experience and an educated level of skepticism. But i think regardless of your thoughts one this particular subject it would be beneficial to ask whether or not you think pwdrhound is truly speaking and advising on a place of personal experience or downright misinformation for malicious or personal gain. Because honestly I am reading your responses as subjective bias versus objective debate. Perhaps one can agree that while you disagree with the level at which pwdrhound is airing on based on your experiences, i think we both can agree that his advice is far from unsafe or bad advice based on his experiences. Especially with a hobby that can bite back with fatal results, no? Sometimes agreeing to disagree with a strong opposition and leaving it at that can further the progress and discussion.

 

I had an extra set that I sold right away. I didn't make a penny on them as I simply let them go at cost. This was not a project I undertook to make money on. After what I went through, for me the hubs were a weak point. For someone with your skill and knowledge, obviously they're not. For me the 300M hubs provide peace of mind. If someone felt like the 300M hubs were worthwhile insurance, I had an extra set they could buy. This is a dangerous hobby and these cars can kill you. Sorry you disagree..

Your testing of spring rates sounds pretty scientific to me. Heaven forbid if a guy like YOU couldn't make it work after driving a strangers car for a few laps it obviously can't be done. What was I thinking? Has it ever occurred to you there is more to getting the whole set up to work besides springs? It's clear you see yourself as the ultimate authority on anything Porsche but man, have you EVER been wrong or is it even POSSIBLE for someone to have success with something that hasn't necessarily worked for you? Obviously not since evidently only you possess the winning formula, in your mind anyway. We should hire you to set up all of our cars Dez. You crack me up man, you really do... cheers!

 

I'll have to save this thread for the weekend!

Its like watching the presidential debate! I came across this searching for "Agency Power SPL Control Arms- Parts?" Who knew!

I believe that both "Chevy and Hound" bring a great wealth of suspension and drivetrain track knowledge but, YOU both have different track experiences.

I envy both on this but, are we really arguing about "Hub failure?"

Chevy, I believe that Hound encountered a failure not once but, twice. If you had a simular problem with your current setup, why wouldn't you look for an alternative to keep your setup the same and remedy the failure point?

Hound, your putting down too much power to the drivetrain for your application. Hence the failure.

You both push the limit and that's why most follow both of you.

I look forward to your settlement on this.

 

I've seen one 6Cup rear hub failure, but that happened on the lap following a contact with another car's front tire, direct hit while cornering.

 

I would be in 100% agreement if he said, if you are going to track this car you should consider replacing the original hubs as all of them are old by now. That's reasonable. But fear mongering based on special case limited information and making false assertions all while trying to unload his spare parts is uncalled for.

John has a wealth of knowledge of the 996 TT platform that's a great asset to the site. I recognize that his and my philosophies are of stark contrast as well. But this particular assertion is incorrect. Hubs are not a weak point. I could elaborate further but there is no way to do so tactfully.