49 CFR Part 571.110 (FMVSS 110)
Tire Selection and Rims and Motor Home/Recreation Vehicle Trailer Load Carrying Capacity Information for Motor Vehicles with a GVWR of 4,536kg (10,000lb) or Less.
49 CFR Part 571.120 (FMVSS 120)
Tire Selection and Rims and Motor Home/Recreation Vehicle Trailer Load Carrying Capacity Information for Motor Vehicles with a GVWR of more than 4,536kg (10,000lb).