So I went away from ordering American Racing rims! I found these Pontiac OEM rims that I like (should fit- I hope ha).
They came with 2x 275/60/R15 BFG's on the rims - correct me if I am wrong, 2008 is the date code (pic below)?? I already bought 2x 235/60/R15's for the other 2 rims (front). Now- question, should I buy 235's for the rear to match, or should I go wider in back- what are the implications?

 

I like the 275's in the rear, they fill up the wheel wells. I think the 235's in the front are a bit small in diameter.

 

yes, 32nd week of 2008

 

The 275's will fill the rear nicely as I always thought smaller tires looked lost in the 66-67 wheel wells.
I have 235/60's on the front on mine. They look good in the front & give some rake with 275's

Those appear to be 7" rims which are a bit narrow for a 275 tire.

You will get more side to side sway with a tall sidewall & narrow wheel.
Also the centers will tend to wear more unless you lower the pressure a bit.
An 8" wheel would be much better.

 

I like your Cutlass Convertible! You better get new tires especially if you’re towing.

 

You can also use wheel spacers on the rear hubs to push your wheels out a bit more - this allows you to use the same size tires all around for ease of rotation and roadside replacement if you get a flat.

 

They are 15x7 indeed. Trying to work with what I've got, so thinking to go not quite as wide as 275, being as it is 7" rim, and the lesser widths are a bit cheaper. As much as I like filled wells. Appreciate the info!

 

That hitch will come off soon. But yes I'll buy new tires to replace those 2008 ones ha.. to bad, they told me they never used those tires because they didn't fit. Seems like a long time to keep tries that didn't fit!

 

Honestly, even a 245 or 255 should be on an 8" rim. a 235 could go either way.

a 255/60 is 27" tall whereas the 275 is 28".
You can try a 255... maybe the tire store will mount one to let you test fit.

 

275's have been run on 7" rims for decades.

 

Doesn't make it right..... I did it myself & posted above about the less than optimum handling & tire wear compared to a properly sized rim.

As you go wider in wheel size, it stabilizes the sidewall & makes for better handling.
Take an off the shelf 275 & measure across the beads, you will likely see an 8-8.5" measurement as manufactured.

I used to run pressures in mid 20's to try & get a normal tread contact patch with a 7" wheel & the centers still wore out.
Put them on an 8" wheel & experienced a definite handling improvement as well as improved traction/tire wear for a given pressure.

 

Great info on helping me decide. Here's a question. The rim is stamped 15x7, but I measure and get 8 inches across. Probably I'm not measuring in the right spot.

 

I measured the bead width of my 275s before installing them. Bead width was 7.5" I don't find any issues with them on 15x7 wheels.

 

I do not have years or thousands of miles of driving on them to judge wear, but have 275’s on factory 7” wheels on the back of my ‘64 and the look can’t be beat. If it were a daily it would be a problem but for a weekend car? Go for it.

 

The Chevrolet SS454 trucks came from GM with 275-60-15 on 15x7 wheels, so there is some precedent for an OEM using them.

 

Had one of those trucks. Nice ride

 

Here's one of mine. 66 442 with 15x8 Hurst wheels and 275/60-15 Nitto 555's

 

wheel width is measured inside bead-to-bead

 

Ok, ok... so from the 'horses mouth'- from BF Goodrich (in this case what I am using), I found the following:
10 years back on the Radial TA tires, the listed 255/60 as the widest you should go on a 7" rim.
Most recently I found on Radial TA tires, the listed max is 245/60 as the widest for a 7" rim.
I do appreciate hearing what everyone has got in actual practice.

 

Actual practice. I had 255-60-15 on 15x7 wheels in back from 1980 to around 2002 or thereabouts when I changed to 245-60 all around. So I can tell ya there were no issues at all with that tire size on 15x7 wheels.

 

Decided to do 235's all around- I don't mind the wheel/fender gap that much, I like the idea of somewhat 'stock' looking wheels. Better than what is on there now, 14" 225's.

 

I like the Pontiac rallies they do make a stencil kit if you decide to go to a more conventional look, I wonder if the olds ss1 caps would fit on them? Be a cool look , I personally think nothing looks better on the early cars than redlines but they be pricey . Great looking car btw

 

Final results! 235 R15's all around on Pontiac rims + OER DK79 High Crown lug nuts