Jim Yanik wrote in
:

"Joseph Meehan" wrote in
:

Clark wrote:
..

Yup, about the tire pressure and that is the key. The weight of the
vehicle is less of a concern than the tire pressure. Although a
heavier vehicle would give a larger contact area for a given tire
pressure.

Well, not exactly. Let's say you have 40 psi in the typical car
tyre.
Making that 100 psi (if the tyre does not pop) and you would likely
have very little difference in contact area because the tyre shape is
determined by the tyre pressure and the tyre construction. Even with
no pressure in the tyre there will be pressure on the surface. So
while pressure is part of the game, it is not the only and maybe not
even the principle player.

The standard method is to place a board or steel plate over the
patch
and drive a car or truck over it. In that case tyre pressure makes
zero difference



a FWD auto usually has approximately 60-40 weight distribution,front to
rear.

I forgot to type;

For a 3000 lb auto,

that's 1800 lbs for the front wheels,divide by two,and you get 900 lbs
pressure on the plate.Since you slightly crowned the cold patch,all that
pressure is compressing it. The plate is to give an even distribution of
pressure on the patch,since the tire contact patch will deflect with the
uneven surface of the patch.

And you can leave that pressure ON the patch as long as you want,while a
tamper gives only a brief pressure.





--
Jim Yanik
jyanik
at
kua.net