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      10-05-2009, 09:14 AM   #46
Gearhead999s
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Drives: E93 335is(wifes)E92 M3
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Quote:
Originally Posted by swamp2 View Post
I seriously doubt this is a factor.



And they have possibly two data points maximum - new-ish tire vs. shaved to a constant depth? It is not inconsistent to have a new partially shaved tire exhibit more traction than a nearly new tire and yet have an extremely worn one have way less traction. So the observations myself and others have made are not really entirely inconsistent with the observations in the book.



Again, see my point just above. I would be a fool to argue against shaving tires to increase grip for many reasons; it is a generally performed and successful endeavor, it has theory on its side and I have no doubt there is plenty of data to support the procedure. However, one point making that not entirely "apples to apples" is that I am talking about a UHP street tires and shaving is generally done on dedicated track tires.

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Let me propose a thought experiment. If you could take a new set of tires, break them in just enough to get rid of their low traction upon being brand new, then do an instrumented skid pad test on it. Have preped in a que 10-20 or so identical sets of tires but shave them say 1/64"-1/32" at a time, mount set each successively and skip pad test them. My guess is that the traction vs. amount shaved will be basically a bump, it will increase for a while, peak and then decrease. It will undoubtedly decrease at some point - say when you hit cords. The question is will is decrease substantially before that point and will it decrease to a point much lower than the nearly new set? I think they will, once near or significantly into the wear bar and at the point when the tread pattern really fundamentally changes I think you will have already lost substantial grip. This is precisely what I believe many of us have observed. Sure UV/aging/thermal cycling etc. may also be contributing through confounding effects. Nonetheless, I think you simply must find this bump shaped curve (before cording).
Ok here I go.I have experiance in this but it was quite a few years ago in the Firehawk series.We normally had our tires shaved at 4/32 and would get 3+ hours out of the highest loaded tires at most of the tracks that we would go with the tires getting to their quickest just before they started to cord and were totaly bald.For the times that qualifying was an issue because of large grids and people being sent home(Montreal Gp,Toronto Indy),the tires would be shaved to 2/32(minimum by the rules) and heat cycled once and saved for qualifying and would usually be a fair bit quicker than the 4/32 tire worn to 2/32 by use.We tried this on some test days to confirm this.Once we figured this out our tires were shaved to the minimum that we needed for the race length at the particular track.This was on spec tires that had a wear rating of 340 not a R-Compound tire by any means.
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