Slakker

Lol powerhound. Your pics make this setup lookup ghetto! But in all serious you make great points. The challenge becomes where to stop. The $10k can become $30k in a blink.

For me, I just enjoy taking 996's and either repurposing or improving them for their purpose. The one rule I have, after taking the hit when I sold my first race car build, is that every piece I add has to add near equivalent value. I don't hit this all the time but at the end of the build it needs to even out. So PMNA is probably out for me.

Edit: On the failure, the bolt broke between the tie rod and wheel carrier. My theory is the nut came loose, got in a bind and snapped. Not sure if it holds water though.

wanna911

Time Trials are a blast. They would suit you perfectly. You have the tool to get it done. And there is the plus of being able to win free tires. I haven't had to buy track tires in 8 years. ($$$$$$$) We're you running full slicks on the car? Do you have a dyno?

Slakker

Here's a picture of the bolt from the other side. The break occurred where the tread meets the base.



I run Pirelli DH scrubs on everything I can. I think R7s are about as sticky but they don't feel near as good to me.

No dyno. Markski told me it should dyno out around 570rwhp. Do I need to find one?

I wish I was going to be in town Labor Day when the TT's come to Hallett. I'd have it ready by then if I was.

powdrhound

Looked at the video. The car appeared very loose in the turn prior to the crash. I would imagine the part failed and it took a few seconds to get pulled out of the upright. You're very lucky you hit a tire barrier and not a hard wall where the outcome would have been very different. I watched a guy crash at Indy and go into the wall. Not pretty. And yeah, you are absolutely right. It's very easy for this stuff to snowball money wise. It's all about managing risk vs. cost and it's an inverse relationship with a moving target as everyones's comfort zone is different.

Rule #1: never ever add up what you have spent on the car.
Rule #2: never ever tell your wife what you spent on the car

This hobby, when you get serious about it and push it to the limit can seriously hurt and/or kill you. Take a look at the suspension parts whose failure can potentially ruin your day and set up a tight stringent maintenance / time out schedule. I've had a number of failures of the same part which cased $5K of damage each time and finally ended up installing a much beefier part to mitigate future failures. It was expensive but still much cheaper than going down the same road.

Take a look at a Cup maintenance catalog and that will give you a good place to start. I'm particularly weary of the outer toe arm attachments and particularly rear LCAs as the outer monoball pin is subjected to tremendous loads with slicks and it's a single shear arrangements on both. Porsche changed the design in the 991 and later GT/Cup cars to a double shear set up that is much stronger and safer. All control arms and toe arms are now double shear on 991Cups but single shear on 997 and earlier. I think this is why Porsche on the 997RSR parts changed the monoball trunnion pin material to 300M to beef it up and mitigate failures.

Incidentally, this appears to be the exact part that failed in your case based on your picture and description. The area at the base of the threads on the trunnion pin is a stress riser subjected to great loads and as I mentioned above, it is a single shear arrangement. Obviously if the retaining nut came loose, that would exasperate the situation. Changing out the rod ends and hardware every few yeas of track use is not a bad idea especially in light of the fact that rod ends and hardware many of the aftermarket suspension components use are very cheap to replace as most are run of the mill parts made by FK and Aurora.

By the way, to preclude any chance of loosening, I never use the OEM lock nuts (with the plastic insert) to retain the trunnion pins of the toe arms / tie rods/ LCAs to the upright. The heat from the brake rotors will eventually break down the plastic and may allow the nut to loosen over time. I always use OEM all metal lock nuts (with the oval opening) and then use another jam nut on top of it for extra insurance (See pics below). This will eliminate any change of developing play and may be something to address if the loosening of the nut lead to your failure.

Finally, I don't think I've ever been able to add equivalent value to the car with any piece I add. I think one would be lucky to get 50 cents on the dollar with most stuff added. Generally, factory/OEM parts will retain more value over aftermarket parts. That's just the nature of race cars and if I'm ever in doubt, I simply refer to rule #1 above. There is simply no other way to rationalize it as the money we spend on these cars will never make sense.

wanna911

Yeah, dyno needed unless you want to run in unlimited. You can use peak hp, or you can use average hp with a numerical dyno plot. That will be significantly lower than peak hp. Divide the weight of the car by hp. Limit is 6.0 hp per lb for TT1. A7's are closer to the start of speed of pirelli scrubs. You take a penalty if you use non DOT slicks too. How much does your car weigh?

Slakker

@powderhound. Great idea on the nuts and a lot of good information to think about. I've had really good luck with the aftermarket but the 6TT does produce a lot more torque and heat then what I'm used to with the C2's.

@wanna911. It's around 3200 with driver and some fuel. I think I can drop around 150lbs fairly easily if need be. I'll pick up a set of A7 and give them a try.

wanna911

That's about what mine weighs. You will need to add some weight most likely as you max hp would be 533. Your average hp will be closer to that number so that will help but you will likely need to run full tanks of fuel each session to be sure. I run with the collapsible spare in to leave no doubts. A few extra lbs isn't worth losing out on hard earned contingency tires.

moburki

Glad everything turned out ok Slakker. On a brighter note, we all get to absorb priceless information from this enlightening thread. Looking forward to your return to track!

Third-Reef

Just a note, that particular failure point is affected by the torque of the nut. Over tighten it and it provides excess tensile stress on the shank that when the joint is pushed to extremes could cause a failure.

Dock

Just wondering; is the use of the symbol "@" in front of a name an extension of the use of Twitter?

manimal

@Dock, I think it started that way, but has since spread to other social media platforms and generally become an accepted convention.

Dock

manimal - the @ symbol automatically triggers notifications on Twitter and other platforms, and that's why it's used there. I don't think there is any such system on Rennlist.

Slakker

It seemed to work.

Dock

It seemed to work here? How so?

Slakker

Dock, you're reputation proceeds you but I'm still pleased that you didn't disappoint. Have a very blessed day.