The 73 I just bought currently has P235/60HR15 tires on it. The spare is P205/60R15. Are either of these sizes correct? If I'm reading the owners manual correctly the tires are listed as GR70-15. Could anyone shed some light on this for me.

 

I believe the GR70-15 most closely matches a 225-70-15 in modern sizing.

 

GR70x15 was the oem tire and the current equivalent is P225/70R15.

 

And, unfortunately, no one makes a repro of a '73 Goodyear or Firestone GR70-15 radial. So you have to go with a "modern" design.

 

Are you really going to put 225/70-15's on it? What type of tires are those P235/60HR15's? That's the only size that we can get tires with traction A temperature A tread wear less than 300...Dunlop makes some. You won't get good rubber in a 225/70-15. Most of us grind some metal off of our emergency brake cable bracket on the rear control arms and slap on some 255/60-15's...they look a lot better.

 

Is this grinding necessary? I was about to order some 255 60/15 to put on my 1971 and don't really want to grind anything. This is on stock 15x8 rally wheels.

 

I'd like to keep the spreedometer as accurate as possible and I don't plan to grind anything for the sake of looks. Will a 70series tire fit into the spare tire carrier?

 

Yes, your 73 came with a full size spare, the previously mentioned GR70x15.

As far as using P255/60R15's, there should be no clearence issues on the rear using a stock offset wheel. 78-82's came with P255/60R15's as an option. There can be minor clearence issues on the front though. GM trimmed the forward edge of the front inner wheel openning lip for extra clearence on 78-79's equipted with the optional 60's. Because of the flared front fenders on 80-82's, this wasn't neccesary.

 

I recommend you try to find one already mounted to see if it fits. I bought two different Goodyear 225/70-15's new, mounted each and neither would fit in the carrier. I ended up buying a 225/60-15 Goodyear Gatorback (at least it matched the rest of the tires 255/60-15 Gatorbacks) to fit in the spare tire carrier.

Good luck... GUSTO

 

GUSTO, When you say that they wouldn't fit, was it because the tires were too wide (sidewall to sidewall) or they were too big in diameter. I would really like to get back to the OEM size, which I believe to be a 225/70/R15

 

For my '73, the spare is a 225/70-15 and it fits just fine in the carrier. If you are interested in changing wheels to 17", you can run 235/55-17 tires. They are very nearly the same height as the stock 225/70-15's so the speedo remains accurate and you can keep a stock tire and wheel for a spare. The 235/55-17's are a little wider than stock but I have no clearance issues. Going to 17's also gets you better choices in performance tires.

As far as clearance for 255/60-15's, I believe the later model C3s don't have any clearance issues with the parking brake cable bracket but the earlier C3s like ours require that bracket to be relocated to the top of the trailing arm. Do a search and you'll find quite a bit of information about this size tire and the clearance issues.

DC

 

DC3, Can you tell me what brand tire you have that is 225/70-15 that fits in the spare tire carrier? Customer service at Cocker Tire the direct cross reference for the GR70-15 OEM tire is indeed a 225/70-15. However, just because that's the equivelent size, that dosen't mean that it will fit in the carrier. They also stated that you could have several tires that are 225/70-15, but from different manufactures and the tires will not all be the same size. So now I guess it's more of picking a brand than a size.
Steve

 

Stephen,

The 225/70's I purchased were both new, and when mounted and inflated they would not fit inside the carrier... The 255/60's on the car, while wider, would fit inside the carrier...go figure. My point in telling you this is you could save some grief and perhaps money by trying an already mounted tire to see if it fits and then purchasing that tire. Tire sizes tend to be nominal... the same size tire from two different manufacturers may not have the exact same diameters when mounted.

I actually bought the tires from Mid America a few years back when they were selling some Goodyear's in 225/70-15.

GUSTO

 

It's some off brand and I'd have to pull it to know for sure. When I swapped my wheels for 17" and got new tires, they set me up with a new 225/70-15 as a spare using the existing 15" rally wheel.

It should not matter who is the manufacturer of the tire. They should all be within a 1/10 of an inch or so in diameter. Go to TireRack.com, click on "Tires by Size" and enter 225/70-15. You should get around 40 choices. Then click on "Spec" for the any of the tires and check the diameter. They should all be close to 27.4 and if not, not far off enough that one would fit and the others would not.

My previous spare was a GR70 and it also fit fine. I could actually put a larger diameter tire in my carrier but I'm not sure how much larger. My 235/55-17's, which are 27.3" diameter, fit fine as well although a little tight due to the extra width.

I wonder if there are different carriers and you somehow have one from a later year?

DC

 

Okay as a first time Corvette owner 1971 LS5 I am now learning that tire selection sucks for 15 inch wheels. I want to keep the stock 15 inch wheels on the car but would rather not put low performance S rated tires on my car. Can anyone tell me what tires are out there for the 15 inch wheel in maybe H rating or better? Also, if I went to a 16 or 17 wheel like the American Racing brand what size tires can I fit on the 1971 in those wheel sizes. I like a staggered look of a smaller tire on the front and larger on the rear.
One last point, I have been checking out the drag radials BFG and others, can anyone tell me if those tires are okay for street driving? What I would like of course is a modern H rated summer tire that is made for performance driving, so if you have something out there please let me know? Frank
P.S. Low cost also helps.

By the way I have 255/60/15 on the front now and they do rub very much so was figuring on dropping to a 235/60/15 on the front soon.

 

255 - 60-15 was the optional tire on later model C3's. They will fit without any issue on the stick wheels. However, every tire is a little different and every C3 is a little different and those tires are a tight fit in the rear. you may need to grind a little metal off the PB bracket to buy a little peice of mind. You could also have a rubbing issue on your rear exhaust pipe if it was installed when the narrower tires were on. you may have to bust the 90 deg pipe loose from the muffler and trim the forward end to pull it away from the tire. If you still have stock pipes you will be OK.

 

I have 245/60-15's all around on my 68, on stock 15" rims. The 235/60-15's are not tall enough and look funny. I had them before because I needed tires and the store couldn't get any 245's at the time. 68's Have 7" rims but that would not make any difference.

 

I was just researching this today and found that the only true high performance tire in the size you want (bolded above-and the size I use for my fronts) is made by Pirelli. It's definitely pricey but if you want a true speed rated tire and one with real grip, here it is at the top of the list in this link. When I'm due for front tires I'll get these if they're still available because I think the extra grip and safety is worth the $.
http://www.tirerack.com/tires/TireSe...60&diameter=15

As for your question about the BFG Drag Radials, I've never used them but from what I've read and heard they are just OK for general use. I chose the Nitto Drag Radial because it has a "V" speed rating and, while it probably gives up a bit in terms of ultimate grip at the strip compared to the BFG, it's a better all around tire for street use. Here's a shot of my Vette with 235/60/15s in front and Nitto 275/60/15s in back to give you an idea of the stance with those sizes. I'm actually about to put the 275/50/15 Nittos on the back because the 275/60s are 8 years old and I want fresh, shorter tires for a pending trip to the strip.

 

I cant find Nittos in 275/50/15's. Where are you getting them?

Thanks

 

LES in the photo what brand is on the front? The stance looks perfect! Did you lower the car or is it stock? Did you have to raise the rear? Had no idea 275/60/15 would fit on the car, to bad no one makes a wider Rallye Wheel! Thanks for the photo and info.