2 points to keep in mind about tire sizes:
The manufacturers tolerances are huge. Actual
diameters will vary wildly, and are also effected by
rim width and tire pressure.
As far as spedo accuracy and the effect on overall
gearing, the car could care less what diameter tire is
on it; it only cares about rolling radius. Rolling
radius is the radius of the tire under the weight of
the car, in other words the distance from the ground
to the center of the tire. It varies with load, air
pressure, load rating of the tire...
jon
--- Kimo Tichgelaar <77MGB@excite.com> wrote:
> Try looking at http://www.tirerack.com , they have a
> page under their tire
> information with conversion and substitution of old
> sizes into modern metric
> sizes. Don't have the exact url handy, but can dig
> it up Monday if it will
> help.
>
> On Sat, 14 Oct 2000 16:17:19 -0600, Phil Bates
> wrote:
>
> | ...Most of our LBS's have an old
> | tire syntax without an aspect ratio listed. I
> like to rallye, so I need
> | to keep my speedo accurate, but may want some
> wider tires on one of my
> | cars (but it's my porsche, not one of my MG's).
> ... Are the aspect
> ratio's different,
> | and does anyone know what they are for the old
> sizes?? I know how to
> | calculate overall diameters if I have the aspect
> ratio.
>
>
> Kimo Tichgelaar
> "A man with a good car needs no justification/
> Fate is in my hands, and in the transmission."
> -Gang of Four
>
>
>
>
>
>
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=====
77 MGB "Christine" slowly, but surely healing
58 Willys CJ-3B, Buick 231, T90, D18, D44, D25, 33X12.5 BFG's, custom exhaust
by Jenson and Audiovox.
She married me not for what I was, but for what she could make me...
I like work; it fascinates me; I can sit and look at it for hours.
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