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  #1  
Old 07-05-2011, 05:58 PM
Jsborn Jsborn is offline
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Location: Pittsburgh
 
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Mein Auto: 2002 M5 (soon)
Question ExtremeContact DW outer edge down to cords--help me prevent

I'd appreciate some help diagnosing this tire problem:

My wife and I shared our 335i at BeaveRun track outside Pittsburgh this past weekend. 8 back-to-back sessions (two different run groups) with only one 20-minute break the entire time meant we were very hard on the car. We were both religious about a very easy cooldown lap and a 2-3 minute slow drive around the paddock.

The brakes, with Hawk HPS pads up front, lasted well. However, the front left tire, which takes most of the load on this clockwise, 10-turn track (only ~1.6 miles), came out looking like someone had cut the outer edge down to the cords with a knife. Rest of the tire has >70% tread depth.

The cords weren't visible until the end of the day, but I noticed a lot of low wear early and thought I was running underinflated, so I pumped up to 45 psi hot.

Any thoughts, aside from negative camber and/or track tires? Now I need another DW tire, however they're all on backorder!
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Last edited by Jsborn; 07-05-2011 at 09:26 PM.
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  #2  
Old 07-06-2011, 03:11 PM
Jsborn Jsborn is offline
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admins--can I get this moved into the tire forum? I think I might have better luck in there. Thanks.
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Old 07-06-2011, 03:49 PM
Z3Papa Z3Papa is offline
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8 run sessions on a tire which was really never intended to be used like this on a stock car with insufficient negative camber. Recipe for disaster. Consider this a learning experience. In the future, if you and your wife want to roll out on 8 20 minute track sessions, you may want to consider dedicated tires capable of handling this and into at least pulling the alignment pins to get some camber or camber plates.
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Old 07-07-2011, 03:02 PM
Jsborn Jsborn is offline
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Location: Pittsburgh
 
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Talked to my shop, a father-son team, both of whom are respected racers in the Pittsburgh area.

Solutions:

1. -1.5 degrees negative camber up front using camber plates.
2. 235/40/18 tires, so a little wider (mostly because 225/40/18 is on national backorder and I'm not willing to replace all 4, but this should increase front grip).
3. Letting the tires cool off between run sessions.
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Old 07-09-2011, 04:33 AM
Z3Papa Z3Papa is offline
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These tires were never meant for tracking. Each tire has their upside/downsides. They are known as a good DD tire with tremendous wet grip. -1.5 really isn't enough given the load on track. Certainly enough on the street. I run -3.8 in autocross and at least -3.0 on tracks. The inherent loading in BMW's is toward to understeer or the outside of the tire. Negative camber allows you to maintain optimal tire positioning upon loading in the corners on track. Letting the tires cools would be a tremendous benefit. Even better would be tires which accept this type of heat.
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Old 07-11-2011, 01:37 PM
jsublime jsublime is online now
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Probably not the advice you're looking for but you can always slow down.
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  #7  
Old 07-11-2011, 06:02 PM
Jsborn Jsborn is offline
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Quote:
Originally Posted by jsublime View Post
Probably not the advice you're looking for but you can always slow down.
Not a bad option--slow in fast out, as they say. It seems obvious that both my wife and I were far overdriving the tire.

At any rate, as Z3Papa suggests, I'll get a different set of tires for the track before I head out to do this kind of driving again. The car seems fine when I'm alone at the track, meaning it has 20+ minutes to cool down between sessions, but I doubt even camber plates will prevent this kind of wear with very little cool-down time on street tires.
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