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Queston about the tyre physics

Ryan Callan

Sep 30, 2008
The tyre's optimal pressure is 86kpa? Which you cannot set in the setup menu. Is there a reason behind an optimal tyre pressure of 86?

Do you know the tyre load figure? Is it around 0.03?

If you equate the dry weight x 10 (Newton) / 4 (tyres) x tyre load + base pressure would you get an estimate of optimal tyre pressures? Obviously this would only be standing stats.

But the weight distribution is not 50/50 so dividing by 4 is a little inaccurate? What is the weight distribution? If (1440x10/4)x0.03+86 you get 192kpa. Does that sound about right?

And tyre temperatures are optimal at 95C but given just a couple of laps and they soar right up to 110 and beyond. Is there a way to combat this?


Jan 1, 2010
lay off the right foot for a few laps. I used to run around 205kpa which is ruffly 32-32 psi in actual tyre terms. Depending on tracks etc and set up... I like my set up quite soft it does move around a bit... but thats all the fun with these cars.


Mar 19, 2009
There may be some confusion over what the "OptimumPressure" parameter in the TBC actually represents. The first number represents the minimum pressure needed to keep the tyre flat on the ground when cold and not on the car. The second number represents the pressure increase per Newton required to keep the tyre flat on the ground when hot and loaded by car weight (one corner). The optimum pressure of the tyres when out on track is actually 214kpa. In the garage the numbers are the cold pressures that you will drive out into the pit lane with.

I calculated a figure of 3530.52 Newtons per corner of the 1440kg V8Supercar. I didn't try to alter the figure for front to rear weight distribution because the V8's can achieve close to 50/50 with fuel onboard and I was trying to get a ball park set of numbers for the one type of tyre. Once I'd arrived at the ballpark it was then a matter of tweaking (fudging) those numbers a little to achieve the right 'flatness' at the optimal pressure. This was trial and error testing over a period of time. The pressure adjustments in the garage allow for the load difference on each tyre which is affected by a number of different conditions, such as fuel load, downforce, track surface and layout, etc.

Now temperatures are another area of difficulty because these pressure numbers along with a multitude of other parameters all have an effect on the tyre temps. Change just one parameter and the whole lot goes out of whack. I find the tyre temps can usually be maintained if you find the 'sweet spot' setup for each track - not that I've done that for many tracks myself :). Tyre temps is one of those areas that may well be revised in future V8 Physics as it is so difficult to get just right. It varies so much from track to track, setup to setup, driver to driver, etc.. Hopefully community feedback will help.