silver 1

i know corvette went to a 225 70 15 in 78 which replace the GR70 15. a lot of people say that that size work for the FR70 15. my car has HR60 15 right now which would be about a 255 60 15, looks good but for ncrs judgeing would a 235 70 15 or a 245 70 15 be a closer match for the GR70 15 than the 225 70 15.

silver 1

looks like the P205 70 15 was for the FR70 15 so the P225 70 15 would be the wright match for the GR70 15 different opions still wanted

Barry O

1973 cars switched to GR70-15 which is 225-70-15 prior to 1972 they were f70-15 which is 215-70-15

Roughrider

gbvette62

The current replacement for a GR70R15 is P225/70R15, not 235 or 245. P255/60R15 is the 60 series equivalent of a P225/70R15. I don't recall what the standard deductions for tires are, and my NCRS Judging Reference Manual is at my shop, but anything other than a GR70R15, will have a similar deduction.

If you have H series tires on your car currently and drive the car at all, I would find a replacement for them soon. As you state, P-metric tires have been in use since 1978, which makes your H series tires are 30 years old. Tires older than 10 years are usually not concidered safe for use at highway speeds.

7T1vette

An "F" width tire is equivalent to a 215 mm for a radial tire. "G" is 225; "H" is 235....etc. You can spend big buck$ on stock "looking" tires from one of the specialty tire outfits...but the date codes, etc. won't be correct so that is probably overkill. 60 series tires look better on the C3 Corvettes, anyway. Just put RWL, 235R60-15's on it and get docked a few points. It'll look , won't it?

silver 1

yes the tires on my car been on her since before 1980 i was looking at tire rack and they said a p225 70 15 for the GR70 15 and a P205 70 15 for the FR70 15. i know that in 78 the changed vettes to 3 options a P225 70 15, P255 70 15 and a P255 60 15. i think my HR60 15 are close to the p255 60 15. for looks i would do a P255 60 15 but for showing i think i'll go with the P225 70 15 thanks for the opions.

gbvette62

There were only 2 tire sizes offered in 78, not 3, but there were 3 different tire choices. The standard tire was the P225/70R15 in blackwall, the first option was the same P225/70R15 in white lettered sidewall. Both of these tires were steel belted radials and were supplied by Goodyear. The second optional tire was the 60 series, P255/60R15 outline white lettered tire. This tire was an aramid belted Goodyear "GT Radial". Your 78 originally had a label on the drivers side door that would have indicated which size tire was originally delivered on your car.

Strangely enough, the 78 sales brochure lists a P225/60R15 white lettered tire as the optional tire, but this is a misprint. The only optional size tire offered was the 255/60, not a 225/60, the option code for this tire was QBS.

silver 1

my car is a 77 i was using the 78 tire sizes to try to match up something i got the 3 different tire sizes from c3 corvette land which had the 2 sizes u said + a P255 70 15 white letter which could be a misprint i guess it should be P225 70 15 white letter ok thanks

Ganey

Silver 1, 225/70/15 is correct. 255/60/15 was a later appearance option at the time. Both about same dia. & will work.

CorvetteRon

[B]I have been using 255/60-15's for about twenty years.
They look virtually stock, and have a good footprint.
But even these are getting harder to get.
Hummm........I wonder if my Camaro's 20"ers will fit.......

BTGRN75

FYI I put BFG 225/70-15s on my 75. The HT. is good, but the tread width compared to my Firestone F70-15 that came out of my spare tire tub is MORE than an INCH NARROWER!

Whats up with that??

Sting & Ray

I'm wondering why you recommend the 235R60-15. It may look right on he car but I doubt it will fit in the spare tire tub. I just purchased a new G225/70R-15 and mounted it on a new 15x8 rallye rim, and my '69's spare tub won't close. I 'd measured the old Goodyear GR70-15 that's still on the original spare rim, and it's section width measured 8-7/8". When I checked the 225-70R-15 specs, it shows a 9" section width. However, the mounted and inflated dimension shows 10". So I'll have to deal with either replacing the tub hanger bolts, or adjusting them - if they have the thread length.