UK Karting - Notice Board (General Karting) : Re: thats what i thought ........

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Re: thats what i thought ........
Posted by 'SimonS' on 21 Sep 2009 @ 22:00

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SimonSJoined: December 2004
Total Posts: 4
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Tyres have two performance characteristics, friction and chemical.

The friction part is a result of the tyre shape, which is determined by pressure

The chemical part is determined by heat, and each set of tyres has a best heat which for karts seems to be between 140 and 160 F. (60 to 70C)

So ideally you want to run at the right temperature and pressure.

Once you have filled your tyres, as the temperature goes up, so does the pressure.

The formula is P1/T1 = P2/T2, that is the tyre pressure divided by the temperature at one time = the tyre pressure / temeprature at another.

So, if you put 1 bar in the tyres at 10C (283 Kelvin) and come back in with the tyres at 38C (311Kelvin, a rise of 10% of the original temperature in Kelvin) then the tyres will be at 1.1 bar pressure.(a 10% rise)(well 1.0989 to be more accurate: 311/283 times original tyre pressure)

But if the tyres are at 1 bar and 20C (293 Kelvin) to start with but still come back with 311 kelvin then the pressure will be 311/293 * the original tyre pressure =1.0614 bar

If you come back with the tyres at 60C (333K) then the pressure will be 333/293= 1.136 bar and if you went out with them at 10C then the pressure is up to 1.177 bar

How much makes a difference? From http://www.f1technical.net/articles/1
on F1 tyres.

"~~~, a variation of just 0.2 kg/cm2 (3psi, 0.2 bar) can “ruin” the performance of the car. "

So, from this we can see that a 10C rise in outside temperature from 10C to 20C will make a difference of 0.04 bar, (0.5 psi) not enough if your pressures are about right to ruin the performance of the tyre but enough to notice.

Message Thread:

tyre pressure and air temp by 'cosgrove78' (21 Sep 2009 @ 13:41)

Re: tyre pressure and air temp by 'NJB' (21 Sep 2009 @ 13:53)

thats what i thought ........ by 'cosgrove78' (21 Sep 2009 @ 16:35)

Re: thats what i thought ........ by 'Doink' (21 Sep 2009 @ 17:31)

Re: thats what i thought ........ by 'SimonS' << You are here!

ok so.......... by 'cosgrove78' (21 Sep 2009 @ 23:10)

You are confusing yourself with .......... by 'Chads' (22 Sep 2009 @ 12:12)

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