Tim:
Most race teams rely on tire tread temperatures to set up suspensions and
tire pressures. Buy an infra red temperature gun. The guns are inexpensive
and provide a great deal of information to the user. The gun that I use is
a Mastercool (http://www.mastercool.com/pages/infrared_thermometers.html).
There must be similar tools available in the UK.
With the gun, use this procedure:
Inflate the front tires to five pounds less than the manufacturer's
recommended maximum pressure;
Inflate the rear tires to two pounds less than the front tires;
Take the car out for a spirited drive and note how the handling
feels (mushy or sliding?);
When you return, check the temperature of the tires at the inside of
the tread (about an inch from the edge), middle of the tread and outside of
the tread - front and rear (take notes of the readings)
Also check the tire pressure to see how much it has increased;
Adjust the tire pressures in stages until the temperature is as close to the
same as possible across all three measurements. Higher in the center,
reduce pressure. Higher on the edges, increase pressure.
Rear tires are easier to match temperatures across the tread because of
solid rear axle.
On the front, caster and camber (not toe so much) can affect temperature
differentials. You are not likely to get exact same temperatures across the
tread.
If, on the front tire, your inside reading on the tread is higher than the
outside (or vice versa), look at your camber settings.
Repeat this procedure over and over until the car feels right and the
temperatures are close to matching up.
For toe-in, use .030 to .060 and you will be fine.
Every car will be unique, depending on weight of the car, tire type, tire
manufacturer and tire size.
Too little pressure will cause the sidewalls to flex excessively, resulting
in a mushy feel and even some wandering.
Too much pressure will cause the tread to lose grip and the car to snap
slide without warning when cornering at the limit.
Eventually, you will find the sweet spot for your car.
Best regards,
Jim Hockert
Dallas, TX
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