Wide tires, flares and related questions

I am interested in this also as I'd eventually like to use the same size rim/tire on my '67. I think what you're interested in is the tire width, from TireRacks site:
A tire's section width (also called "cross section width") is the measurement of the tire's width from its inner sidewall to its outer sidewall (excluding any protective ribs, decorations or raised letters) at the widest point. This measurement is made without any load placed upon the tire
and
The industry rule of thumb is that for every 1/2" change in rim width, the tire's section width will correspondingly change by approximately 2/10".

But a 275 requires a 7.5"-9.5" rim using a BFG G-Force TA as an example for sizing.
BFGoodrich g-Force T/A Drag Radial 2

So at most you might add 2/10" to the stated width for this tire which is 11.1" so say 11.3" since it's also measure with no veh. wt. on the tire.
I was thinking you could mount the rim and cut a piece of carboard in the size/shape of a slice of the tire being 11.3" at the bulge, 9" tread width and 28" overall diam. which should leave ~6.5" high at center from rim edge (28" - 15" rim = 13"/2 for tire top/bottom).

I can tell you that I have 15X7 TTD's w/3.75"bs, 225/60/15 and had to roll my fenders due to sidewall bulge scraping. Your rim will be 1" wider but with a 3/4" deeper bs so that should put your tire sidewall 1/8" farther out than mine at the bulge if the tires have the same amount of bulge. You have to remember to divide everything by 2.

I need to see if I can draw something that can be posted as it would be much clearer. You have a big advantage by at least having the rim already to test fit. If you are planning to buy your tires local I would go talk to them, they should have a tool to test tire size fit also or may mount one to test fit for free if you're going to buy tires there.
Please let us know what you find out.
Jon
For the

We had a 295/35/18's (Toyo RA1's for section width comparison) on a 9.5" wheel on our our car with the only modification being a rolled lip. However, our car doesn't have leaf springs.

I should mention that back spacing and axle width were custom to the application but the tire physically fits in there even with a 2" drop.



-J

you might have a problem in the front with the rim hitting the upper arm when turning. the big wheels (17"+) usually fit over the arm. I went with 15x7 in front, with 4.5 back spacing. it's a little close to the fender with 225 60's on it.

In the rear I went 15x8 with 5.5 backspace, and a 275 50 drag radial, and it's pretty close. I need to get the car moving to see how much rubbing is going on. I think with 275 60 the tire will probably rub.