What do you say happens to the patch then? Take two tyres, identical except
that one is twice the width of the other. Forget different pressures,
different sidewall construction etc that's just chaff. For the patch to
stay the same size the wider tyre would have a patch that was half the
length of the narrower tyre. Are you saying that this is accounted for by
the different squish of each tyre? No way. Why else do high-performance
cars have wider tyres? You could say it is just for show, but single-seat
competition cars like Grand Prix cars don't do anything for show and they
have massively wide rear tyres - wider tyre = more grip because it has a
wider patch. In fact recent Grand Prix rule changes have reduced the
maximum allowable tyre width in an attempt to reduce cornering speeds -
narrower tyre = less grip.
For further confirmation of 'narrower tyre gives more grip in snow' (if any
were needed) see also film of World Rally cars on dry tarmac and snow - dry
tarmac = wide tyres, snow = narrow tyres.
PaulH.
----- Original Message -----
From: Max Heim <mvheim@studiolimage.com>
To: Matt Pringle <pringlmm@mcmaster.ca>; <Ajhsys@aol.com>
Cc: MG List <mgs@autox.team.net>
Sent: Saturday, December 18, 1999 10:40 PM
Subject: Re: Going to look at a '71 B tomorrow
> Again, Matt has the basic idea correctly. The contact patch area is
> determined by the weight of the car and the tire pressure. Period. A
> wider tire does not equal a larger contact area in and of itself. But as
> Allen pointed out, we also have to consider different tire pressures
> (possibly), sidewall construction, rubber (sticky vs. hard, hydrophilic
> vs. hydrophobic), and tread pattern (ratio of tread blocks to open areas
> -- compare a snow tire to a street performance tire). And, as everyone
> has observed, good snow tires seem to have a narrower tread than
> performance tires.
>
> Matt Pringle had this to say:
>
> >I could be wrong here but isn't the "weight per square inch" (ie.,
> >contact pressure) dictated by the tire pressure and not the width of the
> >tire. I would think the a narrow tire would have a contact patch that's
> >longer in the axial direction of the car but not any smaller.
> >
> >Matt
> >
> >Ajhsys@aol.com wrote:
> >>
> >> In a message dated 12/16/99 11:47:37 PM Eastern Standard Time,
> >> niederst@telerama.com writes:
> >>
> >> << One question. It is supposed to snow
> >> around here a bit tomorrow. If I would happen to buy the car, how are
B's
> in
> >> the snow (if the tires are OK)? >>
> >>
> >> - - - - - - - - - - - - - - - - - - - -
> >>
> >> I have driven all my LBCs in the snow in years past. They handle fine
AS
> >> LONG AS YOU KNOW HOW TO DRIVE in the snow. Narrow tires give you more
> weight
> >> per square inch than wide tires. Decent treads will grip the snow.
Don't
> >> slam on the brakes...don't try to turn while braking (which you
shouldn't do
> >> in the dry either)...and don't spin the wheels when you start up.
> >>
> >> Go to an empty parking lot and "cut some cookies" to get a feel for the
car
> >> in snow. If you use your head, there is no problem driving any car in
the
> >> snow. (SUV's not included!)
> >>
> >> Good luck with the B. Hope it is an early Christmas present (read
"almost
> >> concours quality" and they don't know it)!!!
> >>
> >> Allen Hefner
> >> SCCA Philly Region Rally Steward
> >> '77 Midget
> >> '92 Mitsubishi Expo LRV Sport
> >
>
>
> --
>
> Max Heim
> '66 MGB GHN3L76149
> If you're near Mountain View, CA,
> it's the red one with the silver bootlid.
>
|