[TR] tire pressures

[Tony Drews]

I play with the pressures to get the balance of the car to my 
liking.  Now, mine is a race car with vintage racing tires so the 
pressures aren't applicable to the street very much, but I found that 
if I dropped the rear pressures I could get the car to corner with a 
little bit of oversteer which can be fun and fast.  The normal 
"higher in the rear, lower in the front" seems to induce understeer 
in my experience.  I dislike understeer intensely, so play with the 
pressures in my toy cars to where that isn't a problem.  Now my VAN, 
I want certainly DO want to have understeer.

FWIW, I run 25 front and 23 rear with Hoosier Speedsters (cold 
pressures).  If I'm too sideways I'll bump it up to 23.5 rear.  When 
I ran Toyo Proxes they liked 38 to 40 PSI.  Street tires seem to have 
"floppy" sidewalls, so higher pressure to a point gives more crisp 
handling.  I tend to run my street tires near the max rated pressure 
imprinted on the sidewall of the tire.

Tony

At 06:41 PM 8/30/2011, Randall wrote:
> > If you run that much pressure the contact patch area will be greatly
> > reduced and you will wear out the center of the tread first.
>
>My experience with radials has been that, although the center does tend to
>wear out first, the overall wear rate is usually reduced.  The tires
>actually last longer even though they wear a bit funny.  Fuel consumption
>usually improves a bit, too.
>
>Running higher than recommended air pressure also seems to improve handling,
>both responsiveness and ultimate cornering power.  Too much can cause
>handling problems though, including instability at speed and vibration.
>
>So my approach in the past has been to start at the maximum pressure on the
>sidewall, and carefully evaluate handling.  Then cut it by 4 psi and try
>again.  When the handling starts to get worse, you've gone too far.
>
>Don't forget to let the tire cool thoroughly before checking pressure.  The
>measured pressure will definitely go up when the tire is warm; how much
>depends on just how hot it is inside the tire.  The sidewall rating is
>"cold".
>
>If memory serves, last time I went through this exercise, I wound up at 32
>front and 36 rear.  But that was some time ago, and with unusual size tires,
>so may not apply to you.
>
>You also failed to mention what aspects you want to emphasize.  Lower
>pressures tend to give better ride quality and less noise/vibration (which
>is the reason most OEMs go as low as they can on recommended tire pressure).
>
>Personally, I drive the car because it's fun, not because it's cheap to
>operate.
>-- Randall