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      05-01-2009, 08:00 AM   #1
thooooorgal
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Tyres wear - track

Last weekend was sunny, and i finally decided to go to the Nordschleiffe .... birthplace of the M3.

I will not make a summary of this visit to nurburgring .... it was a wonderful day !

But, i have some concerns about the tyre wear. I did only 3 laps, 63 km, and i have detected strange wear of the tyres, on its side .

Is is serious doctor ?



I don't really care for those tyres, as i need to change them soon, but i will go back there, and don't want to have this on new tyres.

Do you know why the tyres wear on its side ? too much / too low pressure ? driving technics ? Is it normal ?

I had checked the pressure on cold tyres in the morning, and use the recommended pressure of BMW F 2.3 / R 2.5 bar, not checked between laps, but i wait some times betwen them.

Thanks for your input.
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      05-01-2009, 09:17 AM   #2
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It is normal to wear the outside shoulders when tracking a stock M3. The camber we run stock isn't enough for tracking the stock tires. Plus the PS2s, even though they have excellent grip, have very poor durability on the track. I think they wouldn't last for more than 3 track days and they are hugely expensive.

However, the stock camber is good for any kind of regular non-track driving. If you plan to track the car often I think it is best to get a set of dedicated wheels & tires for the track.
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      05-01-2009, 11:57 AM   #3
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Your pressure was probably low. 2.3 bar is 33 psi. That's low for track use. I would start out with 37-38 psi and try to keep it around 40 psi (measure hot pressure in between sessions and let air out if it is too high). It is true that the stock suspension does not have a whole lot of negative camber up front, but you'd have to be driving pretty hard and the car would need to be pushing hard into corners (understeer) for this to happen so quickly due to a camber issue. I don't get the impression you were driving that hard. At any rate, this is not a big deal. You just scruffed the tires on the outside a little. Just use higher pressure next time. But if you will track frequently, a dedicated set of wheels/tires would save you money in the long run indeed.
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      05-01-2009, 02:36 PM   #4
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Ya it looks like low pressures and overheating at the edges to me.
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      05-01-2009, 02:43 PM   #5
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i'm used to track my bike more than my car.

With a bike, you need to decrease the tyres pressure on track compared to road use. For example, with a ZX10R, you go from F 2.3 / R 2.5 to F 2.1 / R 1.9 !

I did not do that with the M3, i only checked that the tyres pressure were in line with BMW recommendation.

I'm surprised that you mention it could be too low for track, this is exactly the opposite that for a bike ? you need to increase pressure before track use ??

thanks in advance !
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      05-01-2009, 02:45 PM   #6
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Yup, but even if the pressures were right, you can expect that from a street tire like the PS2. The sidewalls are simply not stiff enough compared to a race tire and together with the stock camber, that kind of wear is to be expected.
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      05-01-2009, 03:50 PM   #7
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I'm lowered on KW Clubsports. The tires are basically flush with the car. I inflated my tires cold to 38 psi front and back. So I'm guessing it should of been 40 during the day. Even higher when pushed, around 41-42. My fronts are at -2.75 degrees and the rears are at -2.25 degrees which is pretty agressive street setup. I noticed this type of wear on the outside of my stock 18's with the stock Michelin Pilot Sports after an agressive run through the canyon. I am not 100% positive this wear wasn't there before my coilovers. Although I noticed the same wear on my 20" rims with Yoko Advan Sports pumped up to 38 psi in the daytime which was at 40 after sliding on the tarmac. Same camber, but the compression/rebound was set a little softer with the 20's. The wear definitely occured after a couple runs through their autocross course and some spins around their skidpad.

BTW this is Sard, bout to go surf with Dean and I'm on his laptop.
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      05-01-2009, 06:59 PM   #8
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His pressures might have been a bit low but I saw that kind of wear also while running 40 psi hot. That's part of what pushed me to R-Comps. I don't want to be buying a set of PS2s every 3 track days.
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      05-02-2009, 04:40 PM   #9
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Quote:
Originally Posted by masmole View Post
Yup, but even if the pressures were right, you can expect that from a street tire like the PS2. The sidewalls are simply not stiff enough compared to a race tire and together with the stock camber, that kind of wear is to be expected.
i agree.
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