Tire Size Dilemma!

[CharBaby]

Heres my situation:

I have owned from brand new, a 1980 PONTIAC Firebird FORMULA V8 4bbl that has the original size tires on the car...225-70-15(27.4" diameter). The size tire that I would like to install is in the size of 255-60-15(27.1" diameter) and I want to keep them on the same original factory PONTIAC 15x7 SnowFlake aluminum wheels that have a Zero Offset.

I have looked up the specs on this size tire and I have done some measuring under the car and it does seem that the 255-60-15 tires will fit front and rear but I hate to get them installed just to find out that there is some rubbing at any of the 4 corners of the wheel well or suspension part somewhere. Also, 7" wide rim is the narrowest width rim that is recomended for a tire that is 255-60-15 so I know that I'am pushing it a bit but, should these tires fit, it's going to look GREAT!

These cars have always needed a beefier tire and the widest tire that I've seen on the 1970-1981 TransAm/FORMULA(at auto shows) of that generation is 245-60-15(26.6" diameter) without changing the offset of the rim. But, when I have asked the owners of those cars wheather they have any information of going to a larger tire, none of them know even as much as I do about their car.

I have searched many a web site in search for this information to no avail. I think that Im on my own here and am looking for a bit of help from anyone who knows these cars.

Is there some extra measuring that I need to do?
Is there something that Im missing?

Thanks to anyone that can help

CB

 

[ET16]

Take a look at http://www.discounttiredirect.com. They have optional sizes listed for your car.

 

[Rumble]

The height would be fine, not sure about the width. You've probably used a tire calculator, but I'll post a couple just in case:

http://www.discounttire.com/dtcs/infoTireMath.dos

http://www.miata.net/garage/tirecalc.html

 

[CharBaby]

Originally Posted By: ET16
Take a look at http://www.discounttiredirect.com. They have optional sizes listed for your car.


Thanks ET16 & Rumble
This I have already done! discounttiredirect is my online tire store of choice even over thetirerack and treadepot along with other online tire stores that I use for reference. I have purchaced 5 sets(of 4 tires) from them along with 2 sets(of 4 wheels)from them in the past 6 years. As a matter of fact, discounttiredirect does list for my Firebird FORMULA, the 255-60-15 as a plus size or + zero size but, it doesn't state weather or not I need to change the "offset" of the wheels. And their customer service is of no help in this area(although very knowlagable otherwise).
All this tells me is that the 2 tires are comparable in tire diameter(27.4 as compared to 27.1) and will not effect my speedometer enough to worry about. What I don't know is weather the tire will rub against anything underneith the body without changing the "offset" and I want to use my factory wheels. This has been a question that I've been dealing with for years.
As I mentioned in my post, I have read the specs on this size tire and have done some rough measurements on the vehicle and came away with..."Man is this close".

Thanks so much for your replies

CB

 

[HTSS_TR]

Another size that may be better fit for your 7" rims and better chance for not rubbing any part of the fender is 245/65-15. The overall diameter is 27.5" as compared to 27.4" of 225/70-15.

 

[CharBaby]

Originally Posted By: HTSS_TR
Another size that may be better fit for your 7" rims and better chance for not rubbing any part of the fender is 245/65-15. The overall diameter is 27.5" as compared to 27.4" of 225/70-15.


Thanks "H" for your interest but, that's not even a tire size that is being made. Never heard of this size before so I double checked all of my sources and nothing shows up. This isn't where Im going anyway! Im looking for old style muscle car type tires such as BFGoofrich Radial TA's, Firestone FIREHAWK INDY 500, GOOD/YEAR EAGLE GT II, Dunlop GT QUALIFIERS(discontinued). There are some tires that I won't even consider such as Cooper COBRA, Kelly Charger, GrandAm or GrandPrix Radial or even PepBoys FUTURA SuperSport. Also, Im looking for tires that have a standard tread pattern(not uni-directional nor asymmectrical). Looking for RWL or (OWL prefered). OWL's are impossible to find except in a truck tire.

 

[CharBaby]

Just spoke to another gentleman from the discounttiredirect customer service line and he assures me that the 255-60-15 tires will fit my car and that's why they have it listed in their "PLUS" sizing catigory. He also mentioned that the 255's are pushing the spec for a 7" wide rim(being the narrowest that is recomended).

Rim Width(inches)= 7"-10"
Recomemded Width - 7.5"

He also says that discounttiredirect will guarantee that if a tire size is listed in their charts, that it will fit the vehicle mentioned without changing the "Offset" of the wheels.
This is the first time any of their customer reps have stated this when I have called them.