235/75 x15 (28.88" x 9.25") is generally considered to be the biggest you can get away with without rubbing during articulation - although some folk claim to get away with 30" x 9.5", but I suspect that they're not disconnecting.
The tyre size that you stated works out at 29.5" x 9.65". I have no doubt that they would rub during articulation, and you'd certainly have to adjust the steering stops. I guess it depends upon whether or not you plan to off-road with 'em.
If it was me, I'd stick to 15" rims, as I'd rather have the increased section height of a 75. You can go up to 31" x 10.50" on standard rims - as long as you have a 3" lift to match
