I'm looking to decrease revs and increase mileage. There's an 8" wheel with 4' B.S. on it now. Will a 285/70 15 fit? It shows a 30.8" diameter, 11.5" section width and an 8.5" tread width.
The 255/70 28.9" dia and 10.1 section width.

What size tire are you currently running?
Stock 66 rearend (or 64-67?)?
Is the wheel lip cut or rolled?

I would say most likely it would not fit without rolling the outer lip...

I run a 295/50-15 on 15X8 wheels on my 66 (stock 66 12-bolt) with no cutting, BUT I have about a 5-inch BS... I also have maybe 1/2 inch clearance on the outside (between the tire and quarterpanel lip)... So a wheel with only a 4-inch BS would likely stick out too far... While it might fit, it might be too close and rub when driving. It might fit if the outer lip was rolled...

Of course, each car/ tire combo will be slightly different, so be sure to measure your own... Also the condition of the suspension can allow the rearend to lean and sway causing some rubbing during cornering, etc...

I'd mount the wheel you want to use and measure from there (either with current smaller tires or even a bare rim... Thats the best way...

I'm measuring the easy way by asking you! ;) I plan on getting a bare wheel on there to measure it the right way soon.
I've only seen those 285/70's on early Hot Rods before. Never on a muscle car. I don't even know if they would look good. Maybe too tall?

A 31" tall tire is going to be a snug fit.

You'll drop about 300/350 rpm at 75 mph - if the tires will fit.

Jimmy, did you trade your '57 for a '66?

Purs, Yes I did! With a fellow MMCC member. Dropped keys. This is the 5th trade I've done in my life. I like it!
I think those 285's would look too big. The 255's would be a little taller and the 275/60 might look better. I'm going to measure everything up. Thanks guys.

Cool! How about some pics of your car? Why don't you bring me that wore out 400 tranny and pick up my wheels and tires? 275/60's in the rear and 235's in the front. They are nearly new! email me if you're interested. bpursley@esc14.net

http://www.chevelles.com/showroom/Purs/rear-edit-copy.jpg

Jimmy, I'm running 275/60 15's on my 66 with 8 inch draglites with 4.5 BS and I have about 1/2 inch clearance without trimming the fender lip. I think a 4 inch BS won't be enough.

Originally posted by Jimmy P:
I've only seen those 285/70's on early Hot Rods before. Never on a muscle car. I don't even know if they would look good. Maybe too tall? I have seen them on a 70 Olds 442 and they look like a real tight fit. they are on 15x8 Weld Pro stars with 4.5"BS and the suspension is stock and the height looks stock. They definitely fill out the wheelwell and are a real tight fit, you can't even stick your finger between the sidewall of the tire and the wheelewll molding. But the owner tells me he has had no rubbing issues and has had four adults ride in it and no problems.

Brandon