Hello.
I'm looking for everyone's opinion on tire sizes for a '76 with the factory aluminum rims. As we all know, the "orginal" size isn't made anymore. Currently, I have 255/60/15 Firehawks on the rims. I have heard that this is the closest to the orginal size, but I have to disagree. The tires look too wide for the car, they rub in extreme turns, and they seem to make the car track imperfection in the road too easily.

Also, if anyone has any ideas for the type of tire let me know. I don't abuse the car so performace isn't really an issue. I'm actually looking for a good all-around tire that is good in the rain (in the rare event I get caught in it!)


Thanks for your thoughts.

Dave K

the best luck Ive had with tires not rubbing is either 245/60 which is still to wide for road imperfections.

or 225/70 which looked to be very close to the original bias ply g70/15 POS tires i took off my lasy vette.

i think size wise it is the 225/70 in fact i read somewhere that g70/15 equtes to about 221/70

http://www.tirexusa.com/tubes/conv_radial.html

this site has a chart to figure out what it should be now

looks like 225/70 is the correct match for gr70/15 with 245/60 as an alternate.

here is a site full of tire size converion links

http://www.1st-4-tires.com/36/metric-tire-size.html

60 series tires weren't made an option on Corvettes until the '78 model year, and then Chevrolet had to make some body modifications so the wider tires could fit properly. Prior to that, 70 series tires were all that were specified for C3's, though the wider profile tires might safely fit individual cars without body modifications, but that is more the exception than the rule.

The original was an F70/15. In a P metric that equals a 225/70/15. Going to a 60 series requires a 255/60/15 to keep a near equal diameter. As stated the 255/60/15 may rub on the body before 78. The recommendation of 245/60/15 is not bad, they should not rub, but they are a smaller diameter. This would make the car travel a bit slower that the speedometer would read. However it would increase rear wheel torque, and provide slightly more acelleration, along with cut in fuel economy. This might be just the ticket for what you want, maybe not.

Any of these should handle on the car fairly well. Every brand has it's own oddities, reguardless of size. Steering response is a bit quicker and overall cornering grip a bit better with the wider 60 series. Wet traction is better with the 70 series, if the tread is similar. Wet traction is greatly varied by tread design.
Ride quality and comfort is better with the 70's, braking and acelleration traction on dry pavement is better with the 60s.

If your car is twitchy on the highway, I would look at steering and suspension as well as tires as a possible cause. The 70s will be less twitchy than 60s just due to a more flexable sidewall, this also means less responsive, but still good.

When I got my car it has 245/60/15. Worn out. Too small around for my purpose, and smaller than original. With the possibility of the 255/60/15 rubbing, I may go with the 225/70/15, but I haven't really decided as of yet. You could go to a 50 series, but based on your statement, I don't think that is what you want.

i just recently went with 255 60's on my 74, i definitely saw an improvement in cornering, and overall traction, i have the firestone indy 500's. 225's just seem too narrow for a corvette to me?? Good luck with your decision.

My '78 had new Goodrich Radial T/A's in P245/60R-15 when I bought it, a size smaller than the recommended 255's. I'm not changing them as they're new and they do handle very well. I can attest to 60 series giving poorer ride quality compared to a 70 series, but better handling, so to get something you give up something. I replaced the bias ply F70-15 tires on my '69 with P215/70R-15 Cooper touring tires. They fill the wheel wells pretty fully, and I'm afraid going to 225's would cause clearance problems. What width tires you can fit on a stock C3 seems very much an individual thing....difficult to make hard and fast recommendations.

Since you aren't concerned about all out performance, consider touring tires like I put on my '69. They're an excellent compromise. Though the car is a 427/435, it rides better than my '78 L82 with the BFG T/A's.

I've had experience with Dunlop Touring tires in the past and was well satisfied with them. I can recommend the Cooper Touring tires as well. Tire technology is far advanced from when our cars were first made.

I have posted this before, but I run 275-50-15 BFG's on the rear and 265-50-15 on the front on my '72. I run the stock rally wheel. I don't know for sure, but I believe the aluminum wheel has the same 4 1/2" back spacing as the rally wheel. I have also seen C-3's with 275-60-15 on the rear with no problems. It depends on what kind of ride quality you're looking for and also the "look" you want.
Reid '72 T-top

Thanks for all your help. It is looking like the 225/70/15's are gonna be the ones to get. The 255/60/15's do rub so they will be replaced with a different size. I know my Vette isn't gonna win any races, so I can sacrifice the cornering. Drivability is the key in my situation.

Thanks again.
Dave K

Because different size rims in the front and back (American Racing Wheels), I have 225-70 in the front and 235-70 in the rear, work out well.