Our 5er currently has 3" of clearance between the top of the tires and the trailer. If larger tires were installed, and that clearance were reduced to 2.5" would those tires rub on the trailer?
much depends on the axle capacity. I've found springs on 5200/6000/7000/8000 /10k leaf spring trailer axles have very little compression/rebound while going down the road. However hit one of those RR track on secondary state highways that can bottom out the suspension. I've had no problems with 2 1/2" at the top. Lots of trailer owners may see tire marks at the top of the wheel well. Most of the time that comes from the suspension walking through a ditch. Most of my other non rv trailers do it but it doesn't hurt anything. Its just a short kiss at 2 mph.