Correct Tire Replacement for 73 vette

[Duke W.]

Re: Correct Tire Replacement for 73 vette

I'm not sure what you're trying to say, but here are some facts. In terms of OA diameter, OA width, and revs/per mile, the GR70-15 and 225/70R-15 are virtually identical.

The following data is for the Goodyear GR70-15 Customgard GT Radial from a seventies vintage catalog.

OAD 27.4"
OAW (6" measuring wheel) 8.65" (9.45" on a 8" wheel)
revs/mile 763

The following data is for the Goodyear 225/70VR-15 Eagle GT from a 12/86 catalog:

OAD 27.44"
OAW (6" measuring wheel) 8.78" (9.58" on a 8" wheel)
revs/mile 760

Nominal dimensions and tolerances for all tire sizes, past and present, are promulgated by The Tire and Rim Association and cover a very narrow range for each size. The nominal GR70-15 and 225/70R-15 dimensions are within acceptable tolerance of each other.

OAW changes by approximately 40 percent of the difference in wheel width, which is how I derived the OAW on the 8" wheel. Both OAWs were specified on a 6" wide wheel, so on a 8" wheel the OAWs would increase approximately 0.8".

Duke

[Peter G.]

Re: Correct Tire Replacement for 73 vette

I don't see that the GR70-15 and the P225/70-15 are identical in size. I have two sets of original GR70-15 tires from Firestone Radial 500 and Uniroyal P2 and both sets are taller and narrower than the Goodyear Eagle GTII and Firestone Firehawk Indy 500. I have ALL these tires! I know I should have my head checked since these are all for just one car! I have NCRS judging tires, driving tires and "vintage tires". With the Corvette only getting approx 1k a year I'll never wear out any tires?

There is a rubbing problem on the rear of the inside frame in the front from turning with the P225/75-15 tires.

The P255/60-15 are even more problematic on rubbing during tight turns that in 1978 they did indeed cut a two inch off the inside lip of the front fenders at the top. I know this was for '78 and '79 but not sure of after that?

[Robert R.]

Re: Correct Tire Replacement for 73 vette

Peter,
Then factor in that most tire experts say that for any "spirited driving" it would be best on tires newer than 10 yrs old. I used to have three sets for the '67 and spent a lot of time changing them out for shows, local events, and winter storage. I promised myself not to do that again with this car.

So for my current ' 73, one set it is. The ones I have do give accurate "speedo" readings, fit in the well nicely and have a great road feel on the highway.

As to the tire looking taller, is it while on or off the wheel? And could tread depth due to wear / usage be a factor as to your comment?

Bob Ricchio

[Jim T.]

Re: Correct Tire Replacement for 73 vette

Robert I installed the Goodyear Eagle GT's on my 70 many years ago and the only time I remember any rubbing was on a left turn onto different road at slow speed, the uneven road caused the tire movement and there was a very slight rubbing of the bottom front fender lip with the tires turned to the left and the suspension movement bringing the left tire up. I later changed my front suspension springs to the F41 "518" springs and had the front end aligned and never noticed anymore rubbing with my 255/60-15.
Wonder if I will get as much mileage out of the current Goodyear GT II's as I have from the Goodyear Eagle GT's? Have 48,737 miles on them now. The current Goodyear GT II's from Tire Rack cost $98, I paid $114.59 for my Goodyear Eagle GT's in 1984.
Another change I made to my 70 when the bumpers and other parts were off for painting in 1990 was the installation of 73-82 rubber type body/frame mounts.

[Harmon C.]

Re: Correct Tire Replacement for 73 vette

David the original poster wanted tires in his first post and in post number three he wanted judging points. I think he has both sides of the answer and the truth is no tires made today get you very many judging points.
Lyle

[Terry M.]

Re: Correct Tire Replacement for 73 vette

Another change I made to my 70 when the bumpers and other parts were off for painting in 1990 was the installation of 73-82 rubber type body/frame mounts.

Those rubber mounts will raise the body about 3/4-inch above the chassis. They may have had more to do with the lack of rubbing than anything else.

[Peter G.]

Re: Correct Tire Replacement for 73 vette

Robert, the only "spirited driving" I do is from 0 to 65 in maybe 8 seconds. When I was young I drove the Chevrolet Corvette for the excitment and now I drive the Chevrolet Corvette for notalgia and to take me back to my youth.

I know there is ALOT of talk now days about "expiration dates" on tires, but I don't think I buy it for my application?

I use to own full service gas stations back in the early 70's and we rode on anything that would hold air! We had tubes, patched tubes and patched tires and even plugged a few too.

Now back then we didn't have a Z06 Corvette doing 140 mph and still getting 28 mpg, but we would never consider buying new tires because they had a nail in the tread at one time or the tire was older than five or ten years.

Like I said I DONOT drive fast in my Corvette and if I keep putting tires on her every five or ten years at the limited mileage she gets the tires would really just start to be broken it?

I know I am in the minority on this subject, but that's just my thoughts on the matter.

[Jim T.]

Re: Correct Tire Replacement for 73 vette

Terry I was not having any rubbing that I remember before I changed the mounts, drove for about 6 years before I changed the mounts and quite a bit of that driving was done with using my 70 as a daily driver and on trips unlike the past 17 years where it sits in the garage for weeks, sometimes months not being taken out for a drive.
I measured the difference between the body and frame before and after the installation of the mounts, it was a lot less than 3/4 inch on my car. I have it written somewhere.
The one incident I had with the lower front bottom of the fender with the left tire when it was turned left was a very minor indication, no destruction, saw the evidence in paint scuff. This occured when the tires were new, more tread wear would of prevented the incident.

[Robert R.]

Re: Correct Tire Replacement for 73 vette

Peter,
I fully agree with you. Back then as long as the tires held air, you were good to go. But now, as we become our Dad (I know I have. I've bought tires for my kids cars after seeing no tread on them, and even though they said that they were OK, because they were as dumb as I was at the same age) about safety.

We have also been spoiled to how comfortable our daily cars perform, and expect our 35 -50 year old cars to do the same.

Now I do have to say that after rolling on the tires that came with the '73 when I bought it (10yrs ago), the new ones are a world of difference.

As to correctness for show points, it will take one of the tire makers to finally make one in GR70x15 like they have done for the earlier models. Until then, the 225 70x15 will have to work.


As soon as I get my camera back, I will post pictures of the setup for you.

Bob Ricchio