<VV> Tire gurus

[Bruce Schug]

On Mar 27, 2005, at 1:46 PM, John Dozsa wrote:

> Mark,
>
> I just bought eight 185/80R-13 white wall tires that closely match the
> original 7.00-13 tires.  Delta Brand.  Tires are marked "Made in
> China".  Spec sheet link at
> <http://www.deltatire.com/catalog/tirelist.asp?tCatID=3>  OD is listed
> at 24.5 inches.  Don't know if it's static or rolling diameter.  The
> circumference measures 78 inches, inflated tire mounted on stock late
> model rims.  Calculated OD = 24.83.  In better spring weather I'll
> measure rolling diameter.
>

John,

These manufacturer's "diameter" figures are always static overall 
diameter, (the tire mounted on a wheel and inflated but not loaded) 
unless otherwise noted.

The actual static overall diameter of an original 7.00-13 was about 
25.3", significantly larger than any 185/80-13 I've ever seen.

This is why Mark wrote that the 7.00-13 is larger in diameter and LOOKS 
larger on a car than a 185/80-13.

However, because of the difference in bias ply tires, like the 7.00-13, 
and modern radials, like the 185/80-13, the revs per mile or rolling 
diameters of these two tires is not proportional to their diameters. 
The 185/80-13 will still not have the same rolling diameter as the 
7.00-13, but, because of these different characteristics, there won't 
be as much difference as there is in diameter.

Understand?

Bruce