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Re: Tire contact area
I am sorry to bug the digest with this mundane topic.... theoretically,
(and geometrically) there is only one tangent point on a circle no matter
what the circumference is.... that said.... the only thing left to produce
a contact patch is the actual deformation of the rubber.... so we need some
chemical engineers and material science engineers to illustrate to us the
deformation characteristics of rubber... or we can forget it please...i
prefer the later option....
happy motoring...
(Embedded image moved to file: pic04966.gif)
Nicolas Roman
Senior Engineering Consultant
North Miami Beach, FL.
jimmy pang
<jimmytmpang@ To: bmw-digest@domain.elided
yahoo.com> cc: NickPashley@domain.elided
Sent by: Subject: Tire contact area
owner-bmw@dig
est.net
06/12/2001
10:55 AM
Please
respond to
jimmyp
All this talk got me thinking, and foolishly, I'm
going to put thought to screen.
Nick, I agree with your arguement, assuming that the
tire(tyre??) is almost incompressible, which it is
not. Each tire supports a certain fixed proportion of
the car's curb weight. This weight should be
approximately equal to the tire pressure multiplied by
the contact patch multiplied by a gravitational
constant. What this constant is depends on if you use
metric or imperial or american units.
so, given that, for both rim sizes, the weight
supported by the tire is the same, and if you keep the
tire pressure the same, THE CONTACT PATCH SHOULD STAY
THE SAME, by virtue of physics, (give or take some
very minor tolerances due to properties of the rubber
being used).
The reduced tire wear is likely due to the increased
tread surface area of rubber on the larger tire from
the increased circumference of the larger tire. Or for
some other reason that my puny mind doesnt understand
right now.
If I'm wrong, then I'm really, really sorry for the
WOB. Ooo.. so much excitement. I think I'm going to
pass out. :).
>I agree with Mr Roman, here is why..........
>If we went to the extremes...... It is plain to see
that with a tyre
the
>same diameter as a golfball, the contact area would
be a lot less than
if
>the tire was the same diameter as the world. OK, as
far as going from
a 16"
>wheel to a 17" wheel, the difference is smaller, BUT
nonetheless the
>difference is there. Whether this difference will be
noticable in
terms of
>tire life remains to be seen, expecially since these
effects are
probably
>thrown into insignificance compared to the effects of
the amount of
hard
>acceleration and hard cornering that the car
does..........
>Nick Pashley
>Principal Technology Engineer
>325i coupe
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