on 7/25/03 7:06 PM, Don Malling at dmallin@attglobal.net wrote:
> Hi Max,
>
> I guess I'm confused.
>
> The tire stores have always told me that the aspect ratio of the old
> standard aspect ratio tires like 155R14 165R14 or whatever was 78. I
> think Kelvin has confirmed that.
>
> I simply do 155 * 78 = 120.9 and then do 175 * 70 = 119 and conclude
> they are about the same height and therefore look pretty much the same.
> I admit I am simply assuming that a 70 aspect ratio tire will not be too
> wide -- maybe that is wrong. Feels like I am missing something here. Am I?
Yeah, you're missing the fact that the number = the width in millimeters. So
155 is not the same as 175. They may look pretty much the same from the
side, but they certainly don't look the same from the front or back.
Also, remember you have to double the calculated section height when
deriving diameter. So the difference between 119 and 121 is 4mm, not 2mm,
which becomes even greater when calculating circumference (the real
functional difference, if you consider appearance or ride height a
non-functional difference).
>
> Most of the 155R14 tires on these parts cars are Michelin X, plus the
> tires look about as old as the cars, so I think we would have to assume
> that both the cars and the tires were in much better condition when the
> tires were purchased and installed. I'm not sure what your point was
> there about buying cheap tires for parts cars.
It's not important, but I was postulating that if I were the owner of a
clapped-out old sports car, and not interested in restoring it, it is likely
that the last set of tires I might have purchased would be the minimum size
available. I was also postulating that this description would likely fit the
PO of a car destined to be broken up for parts. That's all.
--
Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the primer red one with chrome wires
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