contact patch (was 225/50/16 tires on A4?)

[DeWitt Harrison <de@aztek.com>]

On Tue, 04 Mar 1997 14:29:05 GMT, Phil Payne wrote

>> And a 10% wider tire will *not* give you significantly more grip, let
>> alone 10%.  The contact patch remains essentially the same size, just a
>> different shape, and the sidewalls (whose flex is a major factor in
>> handling) are still the same height.
>
>True.  Even if the area increases, the loading per unit of area decreases and 
>the product of the total loading and coefficient of friction remains the
same.  
>Wide tyres when slip has _started_, but not really until.

This has the makings of another exciting techi thread; namely, complex
subject matter, many preconceptions and lots of apples and oranges
comparison potential.

In the interest of ferreting out input from listers who might
have special knowledge about where the rubber meets the
road, I have observed in various car handling and race prep books
that, at any given temperature, the ultimate tire grip in corners is a
non-linear function of tire loading in psi. The general shape of these
graphs is a rising curve where grip increases rapidly with increasing
loading, then flattens indicating a point beyond which increasing
loading - from cornering or braking weight transfer - does not yield
increasing grip.  At that point, the tire begins to break away. It is
my understanding that serious race equipment can pull 1.1g
to 1.2g in a corner. Apparently, this coefficient of friction business
is complicated.

I would be grateful for insight into the value of increasing
the contact patch size for, say, club track events. I suspect
racing or tire development experience would be helpful here.
Thanks for any help,

DeWitt Harrison   de@aztek.com
Boulder, CO
88 5kcstq