<VV> Radial Tire Pressures

[Dale Dewald]

At 08:51 6/15/2010 -0400, Tony Penz wrote:
>What tire pressures should be used for Firestone FR440 P175/180 
>R13?   Don't know if I should use the pressures specified in the 1964 
>Corvair owners manual because they are not for radial tires.  Thanks

You are correct, modern radial tires are designed to run different (higher) 
pressures than 1960's bias ply tires.

First you need to look at the sidewall of the FR440's for the inflation 
pressure required at maximum load rating.  Typically this will be either 
35psi or 44psi. If your tires are rated at 35psi then you would want to use 
about 5psi more than the owners manual recommendation for high speed 
use.  This will typically be about 32-35psii rear and 21-24psi front. Start 
here and make minor adjustments to get the best ride and handling.

If your tires are rated for 44psi you will need to use higher pressures; in 
this case 39-43psi rear and 26-30psi front as a starting point.

One tip is to apply stripes of white liquid chalk across the tread and up 
slightly on the sidewall.  Go to a empty parking lot and make several sharp 
turns at medium speed--enough to make the tires squeal.  If the chalk is 
removed farther up than the edge of the tread surface then you need to add 
more air.

Dale Dewald
Hancock, MI