Need the Front and Rear GAWR Figures for 1960-63 Covair

[RidingOnRailz]

Need the Front and Rear GAWR Figures for 1960-63 Corvair 2 and 4 door Sedans.

Does this information exist anywhere? Someone I know needs to refit their '62 coupe with radial tires as close to OEM bias-ply size as possible.

[maxwedge]

Coker tire has a crossover chart to see comparable sizes, oe to radials.

[RidingOnRailz]

Originally Posted by maxwedge

Coker tire has a crossover chart to see
comparable sizes, oe to radials.

https://www.cokertire.com/tires/amer...whitewall.html

Doesn't tell me what I want to know though.

I want to be able to size tires myself, based on GAWR plus a 10 percent safety margin.

I know in 1960-66, those placards listing gross vehicle weight, and gross weight per axle, didn't exist on cars, but the information must still exist somewhere.

[CapriRacer]

Originally Posted by RidingOnRailz

https://www.cokertire.com/tires/amer...whitewall.html

Doesn't tell me what I want to know though.

I want to be able to size tires myself, based on GAWR plus a 10 percent safety margin.

I know in 1960-66, those placards listing gross vehicle weight, and gross weight per axle, didn't exist on cars, but the information must still exist somewhere.

Back then, car manufacturers tended to use minimal sized tires. That would be a good starting point, since in the many years since, they've increased the tire sizes.

So a 1960 to 1963 Chevrolet Corvair came with 6.50-13 inflated to 15 psi front/ 26 psi rear - except for the wagon (They made a Corvair wagon?) which was 7.00-13 inflated to 15/28psi.

Let's ignore the wagon.

The load carrying capacity of a 6.50-13 at 15/26 psi is ..... well it's a bit tricky. The load tables from the 1960 Tire and Rim Association yearbook only go down to 20 psi. The value at 26 psi is 875#. If I extrapolate down to 15 psi, I get 650#.

And an important consideration is rim width = 5.5.

So allow me to do the math. If we chose a 13" tire from today's offerings, the closest thing is a P155/80R13, but it is 1 3/4" smaller in diameter and requires 3 more psi to carry the same load. But Tire Rack only lists 2 tires available in that size.

A P175/70R13 has more offerings (4), suffers from the same diameter problem, but it has more width and might rub, and doesn't require more pressure to carry the same load.

[RidingOnRailz]

Originally Posted by CapriRacer

Back then, car manufacturers tended to use minimal sized tires. That would be a good
starting point, since in the many years since, they've increased the tire sizes.

So a 1960 to 1963 Chevrolet Corvair came with 6.50-13 inflated to 15 psi front/
26 psi rear - except for the wagon (They made a Corvair wagon?) which was
7.00-13 inflated to 15/28psi.

Let's ignore the wagon.

The load carrying capacity of a 6.50-13 at 15/26 psi is ..... well it's a bit tricky. The
load tables from the 1960 Tire and Rim Association yearbook only go down to 20 psi.
The value at 26 psi is 875#. If I extrapolate down to 15 psi, I get 650#.

And an important consideration is rim width = 5.5.

So allow me to do the math. If we chose a 13" tire from today's offerings, the closest
thing is a P155/80R13, but it is 1 3/4" smaller in diameter and requires 3 more psi to
carry the same load. But Tire Rack only lists 2 tires available in that size.

A P175/70R13 has more offerings (4), suffers from the same diameter problem, but it
has more width and might rub, and doesn't require more pressure to carry the same load.

Hey there! We were just yacking it up on Car Talk direct messager!

See, all I want to do is establish a baseline, 'rule of thumb', or recommendation for cold tire pressures for owners of Corvair 1.0 who decide to convert from bia-ply to radial tires on those vehicles.

Of course it will involve maintaining the historical front-rear cold pressure offset, as you mentioned earlier F:15 R:26psi.

I've heard stories of 1.0 drivers putting in anywhere from 30 to 35psi in all four tires, pressures which I suspect are, for one, too high overall, and secondly, don't preserve the offset engineered into the original setup by GM nearly 65 years ago, in the design stage for the original Corvariants.

I want to leave in here a legacy of guidance, especially with how to preserve that front-rear pressure offset, on Corvairs 1.0 when radials are substituted. And knowing those gross axle ratings would be helpful, even if not necessary.

[maxwedge]

I did a 2 year restoration in my friends shop on a 63 Rampside. When done and back in the owners hands he insisted on running 30 psi in all the tires, he put 14" radials on it. I drove it like and it was scary. Front end bounced all over the road. Finally got him to run 20psi in the front, he was always afraid they looked flat. Lol

[RidingOnRailz]

Originally Posted by maxwedge

I did a 2 year restoration in my friends shop on a 63 Rampside. When done and back in the owners hands
he insisted on running 30 psi in all the tires, he put 14" radials on it. I drove it like and it was scary.
Front end bounced all over the road. Finally got him to run 20psi in the front, he was always afraid they
looked flat. Lol

Sounds reasonable - that last part about 20psi.

One YouTuber about this subject runs F22, R32 on his Vair. Said it handles "like a whole animal, much better"! The Corvair, while nearly the dimensions of my 2010 Honda Accord, sits much lower, both to the ground, and height-overall. Accordingly, it also weighs at least 1,000lbs, even 1,500 less, than the Honda, assuming both Honda and Corvair unoccupied. So the earlier car never needed exceedingly high tire pressures to support, or propel, it.

People also need to be educated on the physical build of radial tires(steel-belted or otherwise). At the nominal/specified pressure, there will always be a slight 'bulge' at the bottom, albeit that will vary with the recommended pressure, and also with the material recipe for different brands of tire.

[CapriRacer]

Originally Posted by RidingOnRailz

Hey there! We were just yacking it up on Car Talk direct messager!

See, all I want to do is establish a baseline, 'rule of thumb', or recommendation for cold tire pressures for owners of Corvair 1.0 who decide to convert from bia-ply to radial tires on those vehicles.

Of course it will involve maintaining the historical front-rear cold pressure offset, as you mentioned earlier F:15 R:26psi.

I've heard stories of 1.0 drivers putting in anywhere from 30 to 35psi in all four tires, pressures which I suspect are, for one, too high overall, and secondly, don't preserve the offset engineered into the original setup by GM nearly 65 years ago, in the design stage for the original Corvariants.

I want to leave in here a legacy of guidance, especially with how to preserve that front-rear pressure offset, on Corvairs 1.0 when radials are substituted. And knowing those gross axle ratings would be helpful, even if not necessary.

The problem here is that the old bias tires were much higher aspect ratio, so there isn't a direct replacement. So any modern tire doesn't get the same pressure as the original tires.

[RidingOnRailz]

Originally Posted by CapriRacer

The problem here is that the old bias tires were much higher
aspect ratio, so there isn't a direct replacement. So any modern tire
doesn't get the same pressure as the original tires.

Oh no, I'm not suggesting a solution where those original 15/26 pressures can be used. That 15psi in front was on the low side, even for the contemporary bias-ply tires in use by default.

I'm just trying to help establish a range of cold radial pressures that will accomplish the same load capacity, and front-back offset for handling and stability.
At least for those who prefer not to go the way of the ready-made Coker solution, as mentioned earlier in this thread, for affordability or whatever reason. Coker offers both bias and radial authentic fits for these Corvairs. I'm just trying to go about it the 'nitty gritty' way, like you and I did off-forum, with that absolute temperature/pressure business.