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[disapr]

One of my cups corded at the track over the weekend so I'd like to figure out what went wrong before I order another set of tires.

These pilot cups were purchased from tirerack.com with the heat cycle option.

Since then they have been used for 12 decently quick track sessions and driven about 400 miles to and from the tracks. The sessions were like this: 4 @ Texas World Speedway (TWS) CCW, 4 @ MSR Houston CW and 4 @ TWS CCW.

My camber was set at -2.2 F -2.0 R when I had the car corner balanced over the summer. I checked the camber just before I went to the track last weekend and it was at -2.1 on the drivers side front and -2.9 on the passengers side front. I moved the drivers side front out to match the passengers side (-2.9) and headed to the track.

After the third session I could see that the shoulder of the passengers side front was looking thin but it wasn't cording. After the fourth session it was done and I had to go home and get my RE11's.

The tire pressure was always set at 31psi cold.


Here are a couple of pictures of the passengers side front.






Drivers side front




Rear (Both are the same)




I know there is a whole document on tuning pressure and camber with a pyro but that's not entirely practical for me when I typically only get 4 sessions and I don't have a crew with a pyro hanging out in the hot pits.

Thanks!

[///M Ryder]

I'm certainly no expert but why did you move the drivers front out to match the passenger front? If your original corner balance was in the -2.2 range it seems like you would have moved the passenger front in to match the drivers front since it was closer to you original corner balance setting. My guess would be the passenger side was already headed for destruction. I'd bet the drivers side is now headed that way since it was run at -2.9.....just a thought...............Phil

[disapr]

///M Ryder - More negative camber (-2.9 vs. -2.2) takes the load off of the outer edge of the tire during cornering and distributes the force more evenly.

My problem is either caused by too little negative camber, too little pressure or a combo of the two. The tires all looked absolutely fine until the third (11th) session and then it corded.

[sawzall]

Do you know what your tire pressures were with the tires warmed up? Low pressures could help accelerate uneven wear.

Edit: Here's a good pamphlet on the PSC, and ideal operating conditions: http://www.tirerack.com/tires/tirete...nd_Feeding.pdf

[Malek@MRF]

Could you please tell me what your TOE settings are?

[disapr]

Originally Posted by shizzle

Do you know what your tire pressures were with the tires warmed up? Low pressures could help accelerate uneven wear.

I didn't get a chance to check them hot this weekend but typically they are 35psi by the time I can check them.

Originally Posted by Malekreza11

Could you please tell me what your TOE settings are?

My toe was set to 0 F and 2 R when it was dialed in last summer.

[///M Ryder]

Originally Posted by disapr

///M Ryder - More negative camber (-2.9 vs. -2.2) takes the load off of the outer edge of the tire during cornering and distributes the force more evenly.

My problem is either caused by too little negative camber, too little pressure or a combo of the two. The tires all looked absolutely fine until the third (11th) session and then it corded.

Roger that.....I understand the camber settings, I'm just thinking about your original setting when you corner balanced. After you switched to the HRE's did you change the settings or did you stay at -2.2? Next Q, did you check the camber after you noticed the cord? If you never set the camber to -2.9 wouldn't that indicate a problem?...........Phil

[AMPowerJ]

You had plenty of negative camber. My bet is that your tire pressure was perhaps too low. 31 seems like plenty cold but you tire pressure gauge could be off. Mine was and I didn't realize it. It read low so I was over inflating my tires. In any case you did get 12 track sessions out of these so I don't think that is awful.

[disapr]

Originally Posted by ///M Ryder

Roger that.....I understand the camber settings, I'm just thinking about your original setting when you corner balanced. After you switched to the HRE's did you change the settings or did you stay at -2.2? Next Q, did you check the camber after you noticed the cord? If you never set the camber to -2.9 wouldn't that indicate a problem?...........Phil

I never changed my settings until right before the last track day. I was planning to dial in -2.6 per a recommendation by another cup user and found that my passenger front was already reading -2.9 so I adjusted my drivers front to -2.9 to match.

I see you're trying to locate root cause on this and I can't answer your question about -2.9 causing the problem - That's why I'm asking others here. To my knowledge more negative camber won't cause extra wear on the outer shoulder of a tire but I could be wrong.

[disapr]

Originally Posted by AMPowerJ

You had plenty of negative camber. My bet is that your tire pressure was perhaps too low. 31 seems like plenty cold but you tire pressure gauge could be off. Mine was and I didn't realize it. It read low so I was over inflating my tires. In any case you did get 12 track sessions out of these so I don't think that is awful.

The gauge is a new longacre so I doubt that's the problem but I'll check it against my other gauges this evening to be sure.

So you think that 12 sessions is good? That's $130 bucks per session in tire wear!!

One more - I'm sure the answer is no but can these tires be mixed? E.g. new fronts with my current rears until they get thin and then new rears and so on.

[persian54]

Knowing hot temps is better than cold.

How are the other tires?

Also, IIRC, doesn't one's toe change if you change the camber?

[wwjd15]

by looking at the pictures and what you have mentioned, my guess they were caused by a few reasons:
1 Shaved. When you have Tirerack shaved them for you, you only had a little tires life left. People who order them shaved because they only use them for very limited laps, such as Time Attack type of racing.
2 Camber. PS Cup has very soft sidewall and shoulder, you need to run more camber. I can't tell you how much without knowing what you have done to your chassis.
3 Understeering / push-under. I can tell your car is very understeer.
4 Improper tire pressure.
5 DSC didn't turn off

Your toe seems ok, the inside of the tires look fine to me.

[disapr]

Originally Posted by wwjd15

by looking at the pictures and what you have mentioned, my guess they were caused by a few reasons:
1 Shaved. When you have Tirerack shaved them for you, you only had a little tires life left. People who order them shaved because they only use them for very limited laps, such as Time Attack type of racing.
2 Camber. PS Cup has very soft sidewall and shoulder, you need to run more camber. I can't tell you how much without knowing what you have done to your chassis.
3 Understeering / push-under. I can tell your car is very understeer.
4 Improper tire pressure.
5 DSC didn't turn off (it's possible, may not be the issue).

Your toe seems ok, the inside of the tires look fine to me.

I didn't select the shaved option, only heat cycling.

My only suspension/chassis mods are KW Club Sports set just above the minimum height specs from KW with mostly JAJ's valving.

[wwjd15]

Originally Posted by disapr

I didn't select the shaved option, only heat cycling.

My only suspension/chassis mods are KW Club Sports set just above the minimum height specs from KW with mostly JAJ's valving.

How did you feel about your car? Understeer or it's ok?
Did you drive with DSC on?

[GTM_Challenge]

The track has banking if i recall? If so were you going counter clockwise there? It would account for higher treadwear on the passenger outter edge. Theyll also run hotter.

Ive run a number of roval courses and the side thats loaded on banked turns always sees more heat and wear.

[disapr]

Originally Posted by wwjd15

How did you feel about your car? Understeer or it's ok?
Did you drive with DSC on?

The car feels pretty neutral but it does under steer unless the weight is over the front tires.

DSC may have been on - It was a cold day.

Originally Posted by GTM_Challenge

The track has banking if i recall? If so were you going counter clockwise there? It would account for higher treadwear on the passenger outter edge. Theyll also run hotter.

Ive run a number of roval courses and the side thats loaded on banked turns always sees more heat and wear.

This track has a huge left sweeping oval section with a high speed left dive into the road course. That's probably a lot of the cause.

[wwjd15]

Originally Posted by disapr

The car feels pretty neutral but it does under steer unless the weight is over the front tires.

DSC may have been on - It was a cold day.

I guess that's the main reason. When E9x M3's don't have the chassis set up to the tires (especially soft shoulder tires like PS Cup, RS3, etc.) with DSC on, the understeering may not feel very precise to the driver, therefore, when you push the car at some high speed corner, the computer will adjust the "feeling" to driver, so, it will end up beating up your tire sidewall and shoulders.

[disapr]

How does the chassis need to be set up for cups?

[wwjd15]

Originally Posted by disapr

How does the chassis need to be set up for cups?

If you can provide some pictures of your car at current ride height and track pictures at both straight and corners, then compression, rebound setting you are on right now. I may be able to help. You can send them over to my email if for better explanation if you want.

However, I can only provide you some suggestion and go from there since I don't have the car.

[dapopa9]

Wow 12 track days is pretty good on 1 set of tires!

[STALKER]

Originally Posted by wwjd15

If you can provide some pictures of your car at current ride height and track pictures at both straight and corners, then compression, rebound setting you are on right now. I may be able to help. You can send them over to my email if for better explanation if you want.

However, I can only provide you some suggestion and go from there since I don't have the car.

What sort of rake do you recommend? 0.5" front to back?

[wwjd15]

Originally Posted by STALKER

What sort of rake do you recommend? 0.5" front to back?

Sorry, what does the question mean? Can you explain a bit?