FW: [NAC] wide wheels with rather narrow tires

[Lawrence C Leung]

Since the tire is effectively a balloon, and we've already established
that for all intents and purposes, the contact patch square area is the
same, irregardless of tire width/section, the reason for wider tires is
to modify the shape of the patch. Wider tires do gain width of patch and
lose length of patch (not as big a deal to a quattro, which can spread
the need for fore/aft traction to 2 to 4 tires vs others, whom use 1 to
at most 2 tires for traction) BUT the gain is not a direct relationship
to tire section width (again, think of the balloon shape). The 205 width
is measured at the sidewall bulge, NOT the tread area. Due to the
"balloon" shape, the gain in inflated treadwidth of the 10 mm increase of
section width is generally at most, about 4 to 6 mm, all else being
equal. Moreover, the loss of front to rear contact patch will not
necessarily match the gain in lateral contact patch, as the shape of a
contact patch is essentially like an oval, so gains and losses can be
acheived at the "corners" of the oval (think Indy Motor Speedway vs a
dorF emblem). To complicate things further, this is assuming a static
(non-moving, cornering, braking or accelerating) contact patch. This
changes as soon as the car is in motion. I'd hate to agree with it, but,
in this case, the increased width will mostly increase the "cool"
appearance of the car, and make it's wheels gain weight. Not much else,
from a performance point of view. Whew!

LL - NY - wishing there were more 215/50-16s avail besides BFG KDWs
instead of 215/55-16s (no room for 225s) b/c I want the added
"peformance" (wink, wink).

On Thu, 18 Jan 2001 08:20:40 -0500 "Theron J. Bliss" <tbliss at mestek.com>
writes:
>Look at what I wrote.  I said "You may gain more contact patch by 
>different
>brands, but comparing the same brand of tire..."  I was using the 
>example of the
>same tire.  If you put a 195/60-15 of THE SAME BRAND, versus a 
>205/50-15 of THE
>SAME BRAND, the 205 will be 10 mm wider!!!!!