Rig Mullin, firs let me welcome you to iRV2.com. We are glad to have you join us here and we look forward to reading of your adventures and experiences. You could have tires that are out of round. Ask the tire installer if they can index the tires onto the wheels and spin balance them. Hopefully this wil take care of the issue but if not the next step would be to see if they are out of round.
Good luck and keep us posted as to what you find.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7