Oversizing tires can cause problems. I put 305/70 22.5's on our DSDP to replace the 275/70 22.5's that it originally came with. I also replaced the 7" wide steel rims with 8.5" Alcoa's. I don't have any rubbing problems when the suspension is aired up. However, I have to make sure the tires are pointed straight ahead when I let the air out or I'd wipe out the fender flares. I could relieve the stiffening rib but then I'd probably get fatigue cracks!
Good thing the OP checked for "kissing" on the rear as that can be a big problem too.
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
Charter Good Sam Lifetime Member, FMCA, SKP
RV'ing since 1957, NRA Benefactor Life, towing '05 Odyssey