Ok, I'm just starting to get into autocross. Back in the day, one of the ways to figure out your optimal tire pressures was to chalk the tires. Put several radial lines of chalk extending from the edge of the tread down the sidewall.

The idea being that as the tire rolled onto its sidewall during cornering it would rub off the chalk. If too much chalk was rubbed off the sidewall you wanted to increase tire pressure so the tire didn't roll as much. And vice versa.

So, I just wanted to know if this is still relevant with today's tires.

If it makes a difference, I'm running Front: Goodyear Eagle F1 Asymmetric 225/40-18
Rear: Dunlop Direzza Sport Z1 Star Spec 255/35-18

I'll probably switch the fronts to Star Specs as soon as the Asymetrics wear out.

 

It's still a good way to find out if you're way out of range, but it's never been a way to find the ideal pressure.

 

 

It sorta seems like an old school method for when people were using different tire technology.

 

Chalking/white shoe polish are better than nothing. To get more serious get tire pyrometer & learn how to use it.

 

I'm of the school of thought that says that the inner ear is the best way to set pressure. Drive the car until the tires are warm and pressures have stabilized. Pick an end of the car, and add three psi. Do another run. Is the car looser or pushier than before? That tells you if the pressure change added or removed grip from that end. Repeat until you've found the ideal pressures.

 

That's the best description I've heard for finding optimum pressures. Nice! I've been using the 'guess and hope' approach mixed in with feeling what the car is doing while raising or lowering pressures universally. This way is MUCH better.

 

[QUOTE=captain_pants,Jun 1 2010, 01:23 PM]That's the best description I've heard for finding optimum pressures.

 

No worries, I'm shuffling over to STR.

 

There was a nice field of STR cars out on Sunday Steve. Do it