<VV> Early tires

Bruce Schug bwschug at charter.net
Thu Oct 20 06:05:15 EDT 2005

On Oct 19, 2005, at 10:52 PM, Chris & Bill Strickland wrote:

> Frequently, when the "non-stock" crowd is talking about what tire 
> sizes they use, they rarely mention the ride height at the same time 
> -- and if you don't think ride height is an important factor in 
> choosing tires for 45 year old cars, well, what can I say? We must 
> disagree.

Bill - But this discussion does not refer to the "non-stock crowd". It 
refers to the "stock crowd", that is, people wanting to put tires on 
their Corvair that match the original tires in diameter. Personally, I 
don't care what size tires a guy puts on his Corvair, I just want them 
to understand what size is the same as the original tire. That's the 
only way he'll know if he's going bigger or smaller. This in turn, will 
affect such things as speedometer and odometer accuracy, revs/mile and 
cruising rpm, as well as heights of the car.

Here's an example. A guy wants to lower his Corvair with smaller 
diameter tires. He thinks this looks cool. Someone tells him that 
175/80-13's match the original 6.50-13 tires. So, he puts a set of 
165/80-13's on. He has, in fact lowered the car, but more than he 
expected. The fact of the matter is that 185/80's were the original 
diameters and the 175's would have lowered it.

Same goes for the aspect ratio. Let's say, this same guy wants about 
the same diameter as stock. He thinks a 175/80 is stock, and someone 
tells him a 185/70 is about the same as a 175/80. But if you look at 
actual diameters you'll find that a 185/70 is quite a small tire; 
nowhere near the original diameter. Without accurate information a tire 
buyer can't possibly make a good decision.

>>   a typical, properly sized and manufactured 185/80-13 tire is very 
>> close to the diameter of an original
> And just how is a lay person supposed to recognize the average 
> non-typical tire?


Good question. In discussing tire diameters I usually refer to 
mathematical diameters - that is, the diameter that the tire should be. 
These can easily be computed or you can go to a number off web sites to 
get them. Now what I'd do would be to take this mathematically correct 
diameter and compare it to the manufacturer's spec. It will probably be 
close. If not, you can use a different size. Manufacturers do vary 
sizes, but they're usually pretty close. Their literature or web site 
or the Tire Rack's will usually give the tire diameter, as well as 
other important specs of the tire you're considering.


Bruce W. Schug
bwschug at charter.net

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