Just ordered some 215/75/15 Silvertowns for my coupe and the "maximum recommended wheel width" is 7.5". My wheels currently have 285/70/15 on them but as close as I can measure with the tires mounted, I think my wheel is 8". Now...the phrase is "maximum recommended." That's kind of an oxymoron..."Maximum" suggests do not exceed..."recommended" suggests there's wiggle room. Would you try it with these 8" wheels or pick up some 7- inchers?
I would think you like a skinnier rim. I have used 215/75/15 wide whites on both 5” and 6” wide rims and they looked great on both. They are currently on 6” steel. I also had 215/75/15 on 6” Torque thrusts and the fit is good and fills the fender perfect.
I would think that you would want to actually dismount the current tire and actually check the actual wheel dimension on the one you already own...if you have my luck you already have 7" wheel width you can use and just purchased a duplicate set....
Drive it up or grab one and drag it to the nearest tire shop. They have a big set of calipers next to the balancer that can measure wheels with tires mounted. Heck, here's one for under 20 bucks. https://www.amazon.com/dp/B09TFVHHH5/?tag=atomicindus08-20 Yes, the 2 words offer an absolute and a suggestion, but that's quibbling. It conveys a feasible upper limit. Blame lawyers. This will drive down the road. It will not be as safe as a proper sized wheel and tire. This is an extreme example, but it points out how the public will do things the tire maker didn't design for and will get questions like yours and also taken into court to explain why they didn't warn the unwashed masses.
There's a lot of variables here... 'Standard' steel rim widths these days are 5, 6, 7, 8 and 10 inch widths, to find 'in between' sizes these days you usually have to look at alloy wheels. Remember also that rim width is inside bead-to-inside bead, not overall width. If measuring overall width on a steel wheel, deduct 1". Now FWIW, there is considerable wiggle room. If you look up 'modern' tires in that 215/75 size you usually get truck tires, with 'recommended' rim widths of up to 8.5". A lower-profile 70 series tire will come up the same. Generally speaking, wider wheels improve handling and going over in rim width a bit will stiffen the tire slightly more improving responsiveness but will also slightly degrade ride quality. Personally, I wouldn't hesitate to use an 8" rim if that's what you have with that tire. This isn't an extreme like the lowrider wheel/tire shown, so it will really boil down to if you like the look of it as mounted. If the 285/70s are what's currently in place, you'll have zero issues with clearances.
It's a fenderless Model A coupe...and I DID buy one of those Calipers. It's either 8 or 8.5, depending on how perpendicular to the wheel you hold it...(another Amazon product with no instructions). I'm pretty sure it's a Wheel Vintiques wheel, so playing around on Summit's site, it's got to be an 8 inch with a 4" back space. Doesn't matter anymore...went ahead and got some 6 inchers tonight with a 3.75" backspace. Fingers crossed, they don't "stick out" too much. I figure that 1/4" shouldn't be noticeable. Should be here by Thursday. Thanks to you all.