<VV> Tire Pressures for 15" Tires - and Other Sizes

Mel Francis mfrancis at wi.rr.com
Fri Oct 2 19:29:54 EDT 2009

Apples and oranges here....

The Corvair is a larger, heavier car on smaller tires.
Porsches are lighter and have never been sold on anything smaller than a 
fifteen inch tire.
The larger the tire, the less pressure is needed to support the same load.

A member who is unable to attend our Milwaukee 50th anniversary event 
tomorrow has kindly loaned me his
'64 convertible, to display at the local Chevy dealership. It's equipped 
with 13" radials and I drove it home
on 20lbs front and 30lbs rear. While those pressures were ok for older 
bias-ply tires, the radials felt way
too mushy at those pressures, so I added 6 more pounds to each tire and now 
it feels much more controllable.
If this car had a set of 15" wheels, 17 front and 25 rear would give just 
about the same 'feel' as the smaller tires.

I recently loaned a set of 15" wheels and tires to a friend with a LM 
convertible and his impression was that the car became
much more controllable, with less tire squeal, compared to the older 
bias-ply 13" tires he had.

As a side-note, I own a nose-heavy '78 Ranchero too, and found that it 
always handles better with about ten pounds less
in the rear tires, just the opposite of the Corvair.

Mel Francis

----- Original Message ----- 
From: "deltainc" <deltainc at grm.net>
To: "vv" <virtualvairs at corvair.org>
Sent: Friday, October 02, 2009 5:51 PM
Subject: Re: <VV> Tire Pressures for 15" Tires - and Other Sizes

> ----- Original Message ----- 
> From: "Ron" <ronh at owt.com>
> Subject: Re: <VV> Tire Pressures for 15" Tires - and Other Sizes
>> Can you explain why a Corvair is best at 32/40 when a Porsche, which is a
>> much better road racing machine, specifies 17/25 ???
>> RonH
> *****************
> 1)  I own the corvair, I do not own the Porsche.  heh heh   sigh
> 2)  The Porsche would probably be a better street road racer at something
> like 32/40.  I would guess the lower pressures are to scare most drivers
> early, and keep them from getting too close to the limits.
> 3)  We are talking street games pressures, and therefore relatively cold
> tires.  Of course, if you were Steve McQueen, with a bubble gum sparkly
> thing you could run around San Francisco for 45 minutes, and build heat...
> you might want to start a little lower in that case.  But if you are
> cruising one lap of St. Louis, and some dude in a rusty 510 Datsun gives 
> you
> the good luck sign and darts off an offramp, you will not have time to 
> build
> heat if you want to play.
> reargards, ken campbell, iou
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