It's all a matter of the right backspacing on the wheel, If you can get the wheel centered in the wheel well. I ran a 245-60-15 on my 66, but had the wheel centered perfect. Not all tires run the same either. A lot of aftermarket wheels come with a 3 3/4" BS and that will limit you to a 225 or less. MS's ride height page has a lot of good information.

You can get a much wider tread by using a 17” wheel because you eliminate the sidewall bulge that is usually a deal breaker with a 15”.  I realize not everyone likes the larger wheels, but you have to figure the tires are the same overall diameter, they just have a bigger hole in the middle, plus wider tread without the sidewall bulge.   All brands are not same width even with same numeric size. My new Nittos are alot wider than Michelins I took off.

Check out the RIDE HEIGHT PAGE.  It was published before most went to larger diameter wheels, so the 15” is well-represented.

I know this isn’t a 15” wheel/tire combo.
However, as already mentioned between tire bulge and backspacing affects your choices the most.


This is widest I’ve had/have on my 65 coupe...so far:

235/60/14 BFG Radial T/A’s
Section width = 9.25” (sidewall-sidewall)
14x6.5 wheel
Backspacing was only 4” (4.25-4.5 would have been better) light scrub with weight in rear...found out this year, I could have shifted axle slightly to eliminate.
Quarter panels not rolled either.
5 leaf mid-eye
KYB GAS A JUST all 4
stock 8” and drums
Granada spindles in front


235/40/18 Pirelli P Zero Nero (this tire runs narrow)
Section width = 9.0” (sidewall-sidewall)
1” wheel spacer
18x7.5 wheel w/5.75” backspacing (4.75” overall)
5 leaf mid-eye
KYB GAS A JUST all 4...Viking coil-overs this spring in front
stock 8” and drums...just converted to 2016 rear discs
Granada spindles in front...65 spindles w/2016 GT brakes this winter

Keep in mind that when more tire is inboard, it may also limit your turns due to frame rail at extremes as well.
The inner part of tire may rub frame rails.
Hope this helps for information.

I have 15" 215's on mine and no issues... I would never go any wider on the front, but it's interesting to see what you guys have done on the rear.
Thanks!

Last edited by Stevo (3/20/2020 7:21 PM)

6sally6 wrote:

Rolling-the-lip on the fenders is pretty much a given...... These cars were NOT designed for 'fatties' back in the day.............unless we put 10" rear shackles and air shocks in the mix!!!
Then the old fashion L-60-15's would hang half-in-half-out!
6s6

I remember L 60s, Had them all the way around my 68 chevelle wagon on 15 x 10 wheels. The Hi Boy look was cool then 
 

This is my 68 with 275/40 rear and 235/45 front tires

I didn't roll the fender lips, but when I replaced the outer quarter's I cut about a 1/4" off the lips just to make them a little narrower. I think it would be fine without modifying the fender lip as long as the backspacing is right. You just want that wheel dead center between the fender lip and the leaf spring. Like others have said, not all tires run the same, a 245 is not always 245.

Now with all that said, my recommendation is to figure out what size fits best, and then buy one size smaller and NEVER have to worry about it. We all want the biggest tire we can cram in there, but nothing is worse that hearing that tire rub. At the end on the day a nice 225 looks real good on a 65/66. 

Thanks Steve, I no longer have the 66, as with four kids and the first couple at college age, it had to go. And if any of you have read some of my other post the 68 is a car I built and mistakenly sold, and just recently got the opportunity to get it back. It is now home for good and going no where. 

I have been bitten by the BIG Tire size bug on more than on occasion and have almost always ended up regretting it. Wether its tire size, motor size, rear end gearing, or beer. Sometimes enough is enough.