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I have a '66 big block roadster w/knock-offs and would like to add red lines. From everything I have read, the closest radial size to original is a 205-75-15. I acquired two brand new Coker Classic red lines in a 195-75-15 that I had planned to put on the front. Should I go with 205's or 215's for the rear? Are the 195's to narrow for the front?
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Re: '66 Tire Size
The obvious: Why do you have 195's if you had decided that 205's were the correct size?
Life will be easier if you keep all tires at 205's. Are 195's too skinny? maybe a wee bit.
The original was a 7.75 x 80 x15. Therefore 7.75 in x 25.4 mm/in equals 196.85 mm. But that is on an 80 aspect ratio tire. If you change to a 75 aspect ratio then one should jump to the next higher cross section width. Which would be a 205. Hence, the 205x75x15 comes close to the original. The choice is yours but I clearly would not intermix a 215 rear with a 195 front. Might get some odd handling. My choice on all my 1965's has been the Michelin X 205x75x15. But then that is a narrow white wall not your intended red wall.
Now there is an alternate opinion provided by some folks who say that one should consider revolutions per mile and select a tire which most closely approximates your original. I think this method requires you to research these values. The problem is that tires of the same outward size may not have the same revs per mile depending on the manufacturer. Therefore you would need to compare the specific Coker red wall tire to the original 7.75x80x15 Firestone from 1965. I'm not sure if all that data is readily available however. The choice is still going to narrow down to 1 of 3 or four sizes.
IF you go to a 215x70x15 the outward physical appearance will be "off" because the tire will look too "fat" although the rev's per mile might be closest to original. In the end the final choice will be a compromise based on your preferences.
Good luck.
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