that is just not logical and goes against what I have learned in car and kart racing.
Well, it's what I have learned in fifteen years of car racing and 100+ track events.
by your logic a driver wants to set up their cold tire pressure the same whether they are racing (driving) in 50 vs. 100 degree weather
That's correct. For example, let's say you are going to the track on a 50-degree day. You set your pressures at 50 degrees - let's say you like the recommended 33F and 40R. When you get to the track, and your car sits for a while, that will be the tire pressure. Go out and do a few laps on the 50-degree pavement, and the tires will heat up, and the pressure will increase. You don't know how much that increase will be. It could go up 3 psi or 5 psi. If you do 10 laps instead of five, it could go up 5 psi or 7. If you drive the car harder, it could go up 8 psi instead of 5. If the track runs clockwise, like most tracks in North America, it could go up 4 psi in the right tires and 6 psi in the left tires. IT DOESN'T MATTER, because - no matter how much the pressure increases - you still have cold pressure of 33F/40R in your tires, and that is your reference point. You aren't shooting for the tires to be X psi when hot, because the amount of the pressure increase from cold to hot can vary, based on so many factors - how hard you drive, how many laps you do, which track it is, etc - but you still have 33F/40R cold pressure in your tires, because that's what they will cool down to.
If you find that you don't like the car's handling, and you would prefer a smaller difference, front to rear, you might let 2 psi out of the rear tires. You measure them first, and it doesn't matter how much you've heated them up or whether they're 42 hot or 47 hot; whatever the measurement is, you let 2 psi out, and they're now 33F/38R when they cool down. If you like the way they handle at that point, then the next time you go to the track, you make sure they're 33F/38R when you measure them cold (at the same outside temperature as you'll be driving them in).
The Tire Rack website has an excellent discussion about this at
http://www.tirerack.com/tires/tiretech/general/pressure.htm In particular, they recommend:
"It’s important to remember that your vehicle's recommended tire pressure is its 'cold' tire inflation pressure. It should be checked in the morning before you drive more than a few miles, or rising ambient temperatures or sun’s radiant heat affects it."
Getting back to David's situation - if he normally inflates his tires to (let's say) 33F/40R in the summertime, then that's a good place to start for the wintertime as well. But that means 33F/40R when measured cold at the same temperatures he'll be driving in. The Tire Rack recommends that if he keeps his car in a heated garage, that he adjusts pressures to compensate. For example, if he's driving in 30-degree winter weather, then he'll want the tires to be 33F/40R at 30 degrees. If he measures the tires cold in his heated garage where it's 70 degrees, as noted on the Tire Rack website, he would want to set them to 37F/44R cold, because they will lose 4 psi when he goes outside where it's colder.
And, of course, getting back to David's original question - yes, winter tires are designed to grip in colder temperatures, where high-performance summer tires don't.
[This message has been edited by nsxtasy (edited 03 January 2002).]
