<VV> Tire Conversion

[Bruce Schug]

You have been given links to some clever tire calculators. While these 
are cool, they aren't quite what I think you were asking for. I think 
you were looking for one of the old "conversion charts" so you could 
look up a stock Corvair tire and then find the modern equivalent of it 
for replacement purposes.

I am not aware of one of these that was really accurate. What they 
typically showed was a tire that had the same load rating, not the same 
diameter or revs per mile. The use of these "replacement" sizes is what 
makes some think that a certain size is the same as an old 6.50-13 or 
7.00-13. But if you study the actual tire dimensions you'll find great 
variances.

For instance, I have a nice chart from an old tire book. It shows the 
equivalents for 6.50-13's to be: B60-13, B70-13, B78-13, and 175-13. 
The diameter of a 6.50-13 is about 24.5" (they varied from at least 
24.1" to 24.6"). I don't know the actual diameters of the others, but 
I'm sure you can see a B60-13 is a tiny little tire. Obviously these 
tires vary greatly in diameter! At the bottom of the tire chart it 
reads, "Size comparison is approximate, and is based on load rating." A 
7.00-13 is not listed on this table.

A second chart shows the same replacements for the 6.50-13. In 
addition, it even lists a B50-13! This chart does show the 7.00-13 and 
shows its equivalents to be the 185-13. This chart also says it is 
organized by load rating.

These charts were sent to me by a Manager of Sales Engineering at 
Bridgestone/Firestone in 1993 when I was doing research on Corvair tire 
sizes.

So that's the problem you have with these charts. Can you imagine a guy 
buying a set of B50-13's, (a tire I have run, years ago) thinking they 
were a 6.50-13 equivalent?

Now for a solution to your problem with your too-small tires. I don't 
think you told us the year of your Corvair so I don't know if its 
original tires were 6.50-13's or 7.00-13's. The only suggestion I have 
is to go to the Coker web site and find the 6.50-13's that Coker 
manufacturers and print out the specs. These show a diameter of 24.58,, 
as I recall. Obviously the 7.00 was larger, around 25.3" in fact, 
although that tire isn't on Coker's web site.

If this doesn't work the only other help I could give you would be to 
send you a copy of the documentation I have on these tires. If you send 
a SASE with about three ounces of postage, I'll send the copies. This 
documentation shows the dimensions of these tires. Based on this, your 
tire dealer could see that the little 165/80-13's they sold you are far 
from original dimensions.

Bruce


On May 27, 2004, at 3:43 PM, Bruce Schug wrote:

> Exactly what kind of conversion chart are you looking for? What do you
> want to know from this chart?
>
> Bruce
>
>
> On May 27, 2004, at 1:50 PM, goofyroo@excite.com wrote:
>
>> Can someone recommend a good online tire-size conversion chart?
>>
>> I found a few using Google but they're owned by clubs -- interesting
>> but you never know what kind of science went into them.
>>
>> I tried www.tirerack.com and found a page claiming to be a tire size
>> conversion chart, but there was no chart there -- just a sample of
>> one.
>>
>> Michael Smith
>> Dallas

Bruce W, Schug
CORSA South Carolina
Greenville, SC
bwschug@charter.net

CORSA member since 1981

'67 Monza. "67AC140"