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The most readily available source of quantitative setup feedback in GPL is to pull into the pits and measure your tire temperatures. So try and extract as much information from the readings as possible. For example, you can tell quantitatively if your car is understeering or oversteering, by monitoring of the difference between the front and rear tire temperatures. If it is understeering, then the front tires will be sliding and so will run a little hotter. You can also tell if your inside rear is spinning under acceleration due to the differential being too open (or dragging because the differential is too closed).
Just taking temperature readings on the start/finish line is a gross over-simplification, of course. GPL accurately models the fast and transient changes in tire temperature in response to cornering, braking and accelerating - this is a large part of why the physics model feels so authentic - so the best way to get decent readings is to sample them at the entry, mid point and exit of every corner. I'm not seriously suggesting we should all be driving for five minutes (to warm the tires up), taking one reading at one point at the track, then repeating this for every sample point. But if some talented hacker could find out where the tire temperatures are held in memory as the program runs, and continually copy those values to a file...
Coefficient of friction - sideways force resisted divided by load applied to tire - e.g. if a tire carried a 1000 lb load it might resist a sideays force of 800 lbs, giving it a Cf of 0.8. |
Steve Smith: “Although how hard you're driving is the most influential factor affecting the temps, other things do have an effect. Stiffer suspension settings, lower tire pressures, more toe (-out or -in at the front; -in at the rear), a heavier fuel load, less power-side lock in the differential, a greater number or severity of turns, even taller ride heights will all tend to increase the temps. Banked turns (like those at Mexico and the Glen) will tend to reduce the temps (less "hysteresis," or squirm). But basically, if you're not getting at least 160° at the front end (which almost invariably runs cooler) and 180° at the rear, you're not driving hard enough.”
I wish I had a graph of coefficient of friction against temperature for the tires. You get the idea - at 72° the tires are too cold and don't grip, at 200° they grip, above 240° they are too hot and start to lose grip. I think the amount of grip steadily increases from 72 to 240°, after which it quickly drops off. In previous Papyrus simulations, the optimum operating temperature range for the tires has been 200° - 240°.
At low temperatures, the tyres are simply too hard - they're not sticky enough. As the tyres "melt" there's an optimal temperature where they are of exactly the right consistency to stick to the road. Above that temperature they are too "greasy" - they're too molten and will flow instead of dig in. This also causes excess wear (though not in GPL).
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