Has anyone had a tire shop claim 225/70/15s are too narrow for the stock 78 wheels? I'm replacing aged (15yr) tires on mine with Cooper cobra's, but the installer had trouble saturday, claiming the wheels tires were too narrow. The same size tire came off them, and these are the factory wheels, like below pic. The new tires are the correct size, not like they were mis shipped or labeled wrong. Ive a feeling it was just a inexperienced or tired installer that had enough work for a weekend.

Anyone ran into this before?

 

Find another shop next time. What they don't realize is the tires are stacked for quite a while and have a tendency to not expand easily when they are hitting them with air thru the valve stem. especially if they left the srader in. when I put the coopers on my factory rally wheels they had to hit them with a blast of air to get them to expand and the bead to seat.

 

I have a 78SA with P225/70/R15/100s on for several years now and when my local Firestone Store installed there were NO narrow issues on my OE wheels.....................Just my 2cents............

JJ78

 

Hello JB,
Remember that for a few years the standard tire was a F70-15 mounted on a 8" wide rim.
The F70 tire is equal to a 215-70-15 tire.
So your new tires are 1 size larger than what was originally on the car.
Regards.....

 

You say both the wheel and the tire are too narrow in the same paragraph?

People often put 255s on them, some even up to 275s. 225s will be fine.

 

Bingo...

 

The rim width range for a Cooper Cobra 225/70r15 6 to 7.5 inches. So yes they are a bit to narrow. The F to P225 size is more about the load capacity and less about it's physical dimensions.

 

I fixed this, the shop was claiming the tires were too narrow, not the wheels, my error. On the guys using 255/60s, I had heard to use this size, your car had to have the fenders trimmed by the dealership back in the day. The old dude who told me that had used the word "tubbed"...I think of actual tubbed innder fenders like a drag car, and he can continued on about the outside fenders being easy to "tub" yourself so i think he meant trimmed.

should I have gone with 255/60s?...its my lady's car, I was honestly just trying to get her fresh rubber instead of the old **** that was on it. They werent even tiger paws, some other no-name label.

 

No trimming needed with my 255/60s...

 

Can you return the tires?

Normally, I'd say yes, you should go with 255/60R15s. That's what's on my lady's 79, though her car came stock with that size tire, as proven by the dealer invoice, and the fenders were trimmed at the factory (or dealership) to make this work.

Lately, I'd say you should just put 18" wheels on any C3, as the tire options for smaller wheels are lacking.

Contact GM for a copy of your dealer invoice, too! Makes a great Mother's Day Independence Day present!

 

Those wheels came stock w 255/60/15

 

The stock tire was P225/70x15. The optional tire was 255/60x15. The dealer did not shave the wheel well, they did it at the factory. It's too late now but next time try the 255's and if they rub, just shave the fender lip your self. I'm not sure what they trimmed..
All the wheels were the same size, 15x8 whether you got the steel or aluminum wheels.

 

These cars look much better with the 255/60R15s and those YJ8 wheels.

Here's a thread that shows what was trimmed. More than I thought. You might get away with no trimming at all. Many do.

https://www.corvetteforum.com/forums...tire-size.html

 

I had a similar issue when I had the latest set of BFG 225/70/15s fitted to our '78. The fitter had a real struggle to get them to "pop" out because, he thought, they had been badly stored for rather too long. I confess that I left him to it so do not know how he got around the issue, but I know they were talking about temporary tubes!

Personally, I would not go with the 255/60 tyres. I'm not convinced they help the car's handling and in my view don't look quite so good - that's just my view!

I'd try an different fitting shop, one that has a little more patience!😄

 

Well they ended up getting them on after all, couple extra spoons and elbow grease. I appreciate everyone's insights on these. Glad to know im not the only one in the 225 camp at least lol

 

The standard tire on the 1978 Corvette was the P225/70R15, mounted on a 15x8 steel rally rim. The optional tire from 78-82 was the P255/60R15 and the optional rim was an aluminum 15x8 wheel. There should be a Certification label attached to the driver's side door, in the area of the latch mechanism that lists which size tire was originally installed on the car when new.

As mentioned above, Chevrolet did trim the lip of the forward edge of the front wheel opening at the factory when the optional 255/60 tires were ordered, but plenty of owners have installed the larger 60 series tires on their Corvettes without any issue. You have to remember that Chevrolet had to deal with things like warranty claims, so even if they found there was only a 1% chance that the tire could make contact with the inner fender lip under a certain condition or maneuver, that was reason enough for them to trim the lip. The need to trim the lip was eliminated in 1980 when the front fenders were redesigned. There is no need to trim the lip with the base 225/70 tires.

While the recommended rim width for a 225/70 is 6"-7.5" it didn't stop Chevrolet from mounting them on 8" rims on Corvettes from 73-82 (73-77's came with GR70x15's, but they are the same size as the 78-82 metric 225/70 tires).

Tire shops (or at least good ones) have bead expanders that go around the tread to compress it to help seat the bead for situations just like what your shop experienced in trying to mount your tires. Bead expanders come in a couple different forms, most inflate but there are also steel bands with a bolt to tighten them.

Mounting tires isn't rocket science, especially with the equipment available to shops today, so as others have said next time "find another tire shop."

 

Just a reminder for us all as we are often installing tire sizes that may not be in high demand. A few years back I was having new tires put on a different C3 than we have now. They had to order the tires in and I checked the dates before they installed them. They were already nearly 4 years old!! I told them thanks but no thanks, checked with my nearby Big O, they got them in the next day and they were 3 months old. Best, Paul

PS: 255's on our '68 with no problems.