<VV> Tire size - no Corvair??

[Bruce Schug]

On Jun 17, 2007, at 10:28 PM, Kinzelman, Andy wrote:

> Guys,
> I am trying to find out the correct tire size for my friend's 
> Maverick.  It calls for C78-14, or D70-14.  I have located several 
> tire size calculators - but none of them can handle the letter series 
> tires available in the 70s.
> Thanks,
> Andy K.

"Correct size" can be quite misleading, as seen in the various 
"replacement" sizes recommended for Corvairs. In recommending a tire 
size to your friend, you must decide what your criteria is.

If you go by the silly "replacement" size charts, you could come up 
with almost anything. You must remember that these charts typically are 
based more on load ratings than tire dimensions. My chart shows a 
C78-14 cross referencing to the following: 6.00-14; 6.95-14; 175-14; 
185/75-14; 195/70-14. Another chart shows: C70-14; 6.95-14; 205/60-14; 
185/70-14; 175/80-14. A third chart recommends: C60-14; C70-14; 
6.95-14; 215/60-14; 195/70-14; 175-14. These are the sizes that a tire 
store would probably try to sell you, if they had them available.

The D70-14 cross references on these charts to the following: D78-14; 
D60-14.

What I would do would be to try and find the diameter of the original 
tire. This is the criteria I use; others may disagree and use other 
criteria.

I don't know how to translate these letter-size tires into modern mm 
sizes. I don't have a chart that does it either. If you really wanted 
to, you could contact tire manufacturers or the Tire and Rim 
Association, like I did for Corvair-size tires and ask them.

I did find a couple of charts that shows a C78-14 to be 25.2" in 
diameter. One, 25.24". One shows the D70-14 to be 25.3", one 25.32".

Corky Coker sells four different Firestone D70-14's that are all 25.40" 
in diameter. Like all tires, these probably varied some but you can 
probably use 25.40" as a "par" figure for diameter. I can't find any 
C78-14's but if you dig around you might.

Based on this quick research it appears that these tires were around 
25.2-25.4" in diameter. Now all you have to do is find a size that is 
near this diameter and you're set.

If you want vintage tires, call Coker or one of the other tire dealers 
that specialize in this type of tire.

If you want a modern mm tire simply look at some specs and find 
something around this diameter. be careful that you don't get too wide. 
Remember, a 50-series tire will be a lot wider than those old 78 or 70 
series tires and, while they may have the same diameter, they won't 
look the same. They also will probably hit the car somewhere and cause 
problems.

Here are some sizes that look close:

195/75-14 - 25.52"

205/70-14 - 25.30"

215/65-14 - 25.00"

I'd be concerned with the width of the 215.

Coker's D70-14's have a cross section of 7.9" which is about 201mm so 
you would probably be okay with a 205.

If your friend was interested in going to 15" wheels he could consider:

175/75-15 - 25.33"

185/70-15 - 25.20"

205/65-15 - 25.49"

If he isn't interested in maintaining the original diameter he can use 
many other sizes.

Note that these tires are essentially the same diameter as original 
Corvair 7.00-13's which are about 25.3" diameter.

Bruce

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

CORSA member since 1980

'67 Monza. "67AC140"