71 Tire Size
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From: Toronto Ontario
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5th Gear
Joined: Aug 2025
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From: Chino, CA
The short answer is that 225/70R15 is likely the best choice for you.
The closest you can get to F70-15 in today's metric sizes is 215/70R15, but those are too narrow for the 8 inch wide Corvette Rallye wheels.
When GM went to radial tires in 1973, they used GR70-15 tires, and when they went to metric radial sizes in 1978, they used 225/70R15 or 255/60R15.
The best choice depends on which wheels you have. Most C3s have 15x8 wheels. With those wheels, either of the GM specified metric sizes (225/70R15 or 255/60R15) will work. You might have to trim the front fenders a bit for the 255s. The front fenders on the 1978-1982 Corvettes had the inner lips trimmed back for more clearance for the wider tires.
If you want to go slightly smaller, closer to the diameter of the original F70-15, then 245/60R15 is the closest to that, and those fit fine on the 8 inch rims.
215/70R15 are really too narrow for an 8 inch rim. If you have the early 7 inch wide rims, or an aftermarket 7.5 inch wide rim, that size will be fine, but its not really safe on the 8 inch wide factory Rallye wheels.
The 225/70R15 are borderline too narrow for an 8 inch rim, but for a light weight sports car, they are within the margin of safety (as compared to medium size SUVS and pickup trucks that also used that size on 7 or 7.5 inch rims).
The closest you can get to F70-15 in today's metric sizes is 215/70R15, but those are too narrow for the 8 inch wide Corvette Rallye wheels.
When GM went to radial tires in 1973, they used GR70-15 tires, and when they went to metric radial sizes in 1978, they used 225/70R15 or 255/60R15.
The best choice depends on which wheels you have. Most C3s have 15x8 wheels. With those wheels, either of the GM specified metric sizes (225/70R15 or 255/60R15) will work. You might have to trim the front fenders a bit for the 255s. The front fenders on the 1978-1982 Corvettes had the inner lips trimmed back for more clearance for the wider tires.
If you want to go slightly smaller, closer to the diameter of the original F70-15, then 245/60R15 is the closest to that, and those fit fine on the 8 inch rims.
215/70R15 are really too narrow for an 8 inch rim. If you have the early 7 inch wide rims, or an aftermarket 7.5 inch wide rim, that size will be fine, but its not really safe on the 8 inch wide factory Rallye wheels.
The 225/70R15 are borderline too narrow for an 8 inch rim, but for a light weight sports car, they are within the margin of safety (as compared to medium size SUVS and pickup trucks that also used that size on 7 or 7.5 inch rims).
Melting Slicks
Joined: Apr 2021
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