<VV> Tire gurus

[airvair]

That may be, but I've never seen any manufacturers specs on what the 
rolling diameter is on a 7.00-13. That tire was long out of production 
by the time I started looking at rolling diameter. All I can say is what 
is listed on the speedo head, for better or worse, regardless of what 
Chevy said or did. And 825 revolutions per mile mathmatically calculates 
out to 24.44 inches in rolling diameter. You going to dispute that math?

If what's on the speedo head is to be believed, and the math calculates 
as correct, then why can't we use as the correct size of tire one with 
the correct 24.44 inches rolling diameter? All the 185's I've seen seem 
to list a smaller rolling diameter.

At least we can agree on rolling diameter being the critical dimension 
for accuracy. Glad that you also agree with the visual assessment. At 
least then I'm finally making headway.

-Mark

BobHelt at aol.com wrote:

> In a message dated 3/27/05 9:03:36 AM US Mountain Standard Time, 
> airvair at richnet.net writes:
>
>> BTW if you look on the speedo housing label on a late model, it will see
>> that it is labeled as factory-rated for 825 revolutions per mile, which
>> translates into a rolling diameter of 24.44 inches. Just try to find a
>> 185/80R-13 tire listed as having THAT rolling diameter! (And FYI, I once
>> checked an authentic set of 7.00-13's for rolling diameter, and they
>> came within just a few feet of being dead-on in a measured 5 miles. Sure
>> must have been a true 24.44 inches in rolling diameter.)
>
>
> Mark,
> I fully agree on the physical appearance of the 7.00s looking larger, 
> but as I said the actual specs show nearly identical revs per mile for 
> these two tires. (You're goinging to argue with the specs?) 
>
> Also you and I both know that Chevrolet, like all other 1960s car 
> manufacturers, designed their speedometers to read fast. So the 825 
> can't be used for a true speed representation. Revs per mile is the 
> only true way to show equivalency.
> Regards,
> Bob Helt