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uploaded 8/10/2007

Formula 1 Tire Graining

The 2007 Formula One race in Hungary was a crazy event with lots of weird happenings. One of the challenges facing the race teams was tire graining. An excerpt from my book gives a detail explanation of give-up, graining, heat cycles, and blistering.

During the telecast of the Hungarian GP on Speed last Sunday Steve Matchett, the former Benetton mechanic who is the technical analyst, said, "It's called graining because the rubber rolls off into grains. Laying down more rubber will increase grip and help with graining."

A more accurate description would have been, "It's called graining because the tire surface takes on a grainy texture. The soft, adhesive tread surface digs into the track texture, gets deformed into waves, and as sliding continues the waves turn over wearing rubber off the upstream side of the wave. When the sliding stops the deformed rubber snaps back leaving a peak pointing against the direction of travel. As more rubber is laid down during the race, grip will be reduced and there won't be enough side loading on the tread surface to start the wave formation."

Steve is a smart, very articulate guy with a lot of experience. The basic errors in his description of graining just shows how complicated tires are and how much misinformation exists even, or maybe especially, among experienced racers.

Steve could have added that a poorly balanced car maybe one with excess understeer will grain the front tires more readily than a better balanced car. Since some drivers need more understeer for comfort than others, driver style can also contribute to graining.

I'll bet another factor is the relatively light loading of F1 tires. The contact patch is wide and the cars are light. I don't think you'd see that same type of graining at NASCAR events. Of couse the rubber formlations of Goodyear and Bridgestone are entirely different.

It would be fun to hear graining stories from racers. Photos too.



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