Date of change of tire size from, e.g., 7.75 x 15 to F78-15?

[Bob B.]

Hi all,

Just curious as to when the transition of tire sizes took place from the older, for example, 7.75 x 15 to the letter/number style such as F78-15? Specifically, I'm wondering if Goodyear Polyglas GT F60-15 raised white letter tires were available in 1966 or did they come in in the late 60's?

Thanks,

Bob

[Joe L.]

Re: Date of change of tire size from, e.g., 7.75 x 15 to F78-15?

Hi all,

Just curious as to when the transition of tire sizes took place from the older, for example, 7.75 x 15 to the letter/number style such as F78-15? Specifically, I'm wondering if Goodyear Polyglas GT F60-15 raised white letter tires were available in 1966 or did they come in in the late 60's?

Thanks,

Bob

Bob------


I believe the transition to alpha-numeric sized fiberglass belted tires began for the 1967 model year but, of course, not for Corvettes. However, the Goodyear Polyglas GT tires were not available that early. I believe they came along about 1968 or 1969. I recall I put a set of these tires on my 1968 Chevelle SS 396 sometime before I sold it in September, 1969. Many of the "muscle cars" like Mustang GT-350, Roadrunners, Chevelle SS 396, etc. started using, at least as an option, the alpha-numeric, fiberglass belted, bias ply tires for the 1967 model year.

Of course, fiberglass belted tires were never used on a Corvette. Corvettes went from alpha-numeric size, bias ply tires in 1972 to steel belted, alpha-numeric, radial ply tires for 1973.

By the way, I used the Goodyear Polyglas GT tire for many years on my 1969 Corvette after the original tires wore out. These tires provided a very harsh ride but the car never handled better. Handling suffered somewhat when I had to switch to steel belted radials when the Polyglas GTs were discontinued.

[Bob B.]

Re: Date of change of tire size from, e.g., 7.75 x 15 to F78-15?

Joe,

Thanks! The car had Torque Thrust wheels on it, but the picture taken when it was on the track in 1966 looks like just blackwall tires. A picture taken later showed the Goodyear Polyglas tires. I guess I'll just look for a good set of correct vintage style tires that they had in 1966.

Bob

[William C.]

Re: Date of change of tire size from, e.g., 7.75 x 15 to F78-15?

Really depends on make/model. Looking at some old Tire-Battery Accessory catalogs, the first Letter size tires show up in 1967, on Barracuda, and 1968 Camaro/Corvette for the first GM application. Corvette 1968, Camaro 1968, (partial) Chevy II 1968 (partial) and on from there...all 1966 models would use a tire from the old X.yz - rim size system