I have a 70 442 W-30 that I am going to switch to 15" SSIII stock rims.
I am trying to lower the RPM on the highway and fill the wheel wells better.
I was thinking of using 235/70's on the front and 255/70's in the rear.
Has anyone used this combination?
The 255/70 has a diameter of 29" which will lower my RPM by about 500, which is what I am looking for.
Will I have any fit problem in the rear with 255/70?
Thanks,
Joe

 

I do not think you would have an issue - hopefully someone with that size will respond. I have 255/60 on the back of my car and there is plenty of room.

 

Thanks Steve,
It looks like we are twins!
Love the color.
Joe

 

I have 245-60s all around. Only issue is a slight rub on stabilizer bar in front if I turn the wheel all of the way.

 

The rear wheel wells are large enough to fit 325-50-15s (with the right backspacing) and I see lots of folks with 276-60s on factory SSIII wheels, so I suspect you wouldn't have any issues with a 255-70.

Here's an old thread with some good wheel/tire info:
https://classicoldsmobile.com/forums...gest-tire.html

 

Sorry to resurrect an old thread, but you guys seem to know what I don't. I have a lead on a set of 275/60/15 tires on deep rims for my 69 Cutlass. Wondering if they'll fit inside my rear wheel wells. They apparently fit an 81 Monte Carlo with spacers. What to you think?

 

The tires alone will definitely fit in the wheel wells (many folks run even wider than 275-60s) but they might not while mounted to those wheels. Depends upon the backspacing. Do you know how wide the wheels are? Can you measure to get the backspacing?

 

What are "deep rims"? Without knowing the offset and width, it is impossible to provide a useful answer.