Here's an old autocrosser trick to show the where the contact patch ends.

o Get a bottle of white shoe polish that comes in the squeeze bottle with the
applicator.

o Put a stripe starting about 1 inch up the outer sidewall down to what will
definately be contact patch on the tread block.  Do this at 4 or 5 points
around each tire.  Note that this may not come off easily, or completely.

o Adjust your pressures to the test values.

o Do about a 1 mile run with hard, or in a vanagon, sort of hard, cornering
both directions.  Speed is not critical, just side load.  Tires should be at or
near operating temp before starting this, though.

o Check what got scrubbed off.

o Renew the shoe polish.

o Change pressures.

o Lather, rinse, repeat.

This will allow you to adjust for maximum patch for your tire on the surface of
your choice.  That may not be best grip, but should be very close.  Note that
this is temperature dependant, and surface dependent, but again will get you
much closer to best grip than other methods costing the same as a small amount
of shoe polish.

tom

------
Tom Ring K0TAR, ex-WA2PHW  EN34hx
85 Westphalia GL Albert
96 Jetta GL The Intimidator
taring@taring.org

"It is better to go into a turn slow, and come out fast, than to go into a turn fast
and come out dead." Stirling Moss