§393.75 Tires.

  1. No motor vehicle shall be operated on any tire that (1) has body ply or belt material exposed through the tread or sidewall, (2) has any tread or sidewall separation, (3) is flat or has an audible leak, or (4) has a cut to the extent that the ply or belt material is exposed.
  2. Any tire on the front wheels of a bus, truck, or truck tractor shall have a tread groove pattern depth of at least 4/32 of an inch when measured at any point on a major tread groove. The measurements shall not be made where tie bars, humps, or fillets are located.
  3. Except as provided in paragraph (b) of this section, tires shall have a tread groove pattern depth of at least 2/32 of an inch when measured in a major tread groove. The measurement shall not be made where tie bars, humps or fillets are located.
  4. No bus shall be operated with regrooved, recapped or retreaded tires on the front wheels.
  5. A regrooved tire with a load-carrying capacity equal to or greater than 2,232 kg (4,920 pounds) shall not be used on the front wheels of any truck or truck tractor.
  6. Tire loading restrictions (except on manufactured homes)
  7. Tire loading restrictions for manufactured homes
  8. Tire inflation pressure
    1. No motor vehicle shall be operated on a tire which has a cold inflation pressure less than that specified for the load being carried.
    2. If the inflation pressure of the tire has been increased by heat because of the recent operation of the vehicle, the cold inflation pressure shall be estimated by subtracting the inflation buildup factor shown in Table 1 from the measured inflation pressure. See FMCSR 393.75 for Table 1.