I autocrossed an MR2 for several years. At one point I
didn't have R1's so I used my Dunlop(dontstop)D60's.
The sidewall rolled very badly. I kept increasing
pressure until I got to 70psi with no improvement. It's
not much fun losing an autocross while destroying your
street tires. One of the good things I noticed from the
softer sidewall tires is increased warning before
breakaway. Unfortunately, they broke away much sooner
than stickies. I guess that is why bias ply racing
tires are so popular. They give better feel of what is
about to happen.
Andy
> If the sidewall rolls enough, the inner shoulder of the tire will come up,
> reducing the contact
> patch. Yes, the main effect of higher pressure is quicker response to input
>due
> to the stiffer
> sidewall. But it's hard to overinflate a radial enough to get it to bulge in
>the
> center and really
> reduce the contact patch. When I was autocrossing the SE-R on street tires, I
> kept bumping the tire
> pressures and it kept sticking better and better. I finally stopped at 50psi.
> The BFG R1's, which
> were autocross tires, were happiest at 34psi.
>
> andycost@att.net wrote:
>
> > There have been several comments on air pressure. A
> > lower air pressure will give a softer ride while
> > increasing contact patch and adhesion. A higher air
> > pressure will give a harsher ride, lower temperatures,
> > and increase slip. The sidewall rolling under does not
> > effect the adhesion of the tire much. It does effect
> > the feel and responsiveness as the tire squirms in
> > relation to the rim.
>
> --
> Gordon Glasgow
> http://www.gordon-glasgow.org
>
>
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