Tread Condition Tread Depth and Wear Pattern not result, adherence to the landing surface is reduced. Over  a long period of time, over inflation leads to premature tread  wear. Therefore, over inflation reduces the number of cycles  in service before the tire must be replaced. It makes the tire  more susceptible to bruises, cutting, shock damage, and  blowout.  [Figure 13-134] Condition of an aircraft tire tread is able to be determined while  the tire is inflated and mounted on the aircraft. The following  is a discussion of some of the tread conditions and damage that  the technician may encounter while inspecting tires. When checking tire pressure, allow 3 hours to elapse after  a typical landing to ensure the tire has cooled to ambient temperature. The correct tire pressure for each ambient  temperature is typically provided by the manufacturer on a  table or graph.  could land with underinflated tires that may be damaged due  to over-temperature from flexing beyond design limits as  described above. An increase in tire pressure before takeoff  in Phoenix, Arizona prevents this problem as long as the  tires are not inflated beyond the allowable limit provided in  the maintenance data. In addition to overheating, under inflated aircraft tires wear  unevenly, which leads to premature tire replacement. They  may also creep or slip on the wheel rim when under stress or  when the brakes are applied. Severely under inflated tires can  pinch the sidewall between the rim and the runway causing  sidewall and rim damage. Damage to the bead and lower  sidewall area are also likely. This type of abuse like any  over flexing damages the integrity of the tire and it must be  replaced. In dual-wheel setups, a severely underinflated tire  affects both tires and both should be replaced. Over inflation of aircraft tires is another undesirable  condition. While carcass damage due to overheating does  Evenly worn tread is a sign of proper tire maintenance.  Uneven tread wear has a cause that should be investigated  and corrected. Follow all manufacturer instructions specific  to the aircraft when determining the extent and serviceability  of a worn tire. In the absence of this information, remove any  tire that has been worn to the bottom of a tread groove along  more than  1 ⁄ 8 of the circumference of the tire. If either the  protector ply on a radial tire or the reinforcing ply on a bias  tire is exposed for more than  1 ⁄ 8 of the tire circumference, the  tire should also be removed. A properly maintained evenly  worn tire usually reaches its wear limits at the centerline of  the tire.  [Figure 13-135]  Figure 13-134.  Tires that are overinflated lack adherence to the runway and develop excess tread wear in the center of the tread. Tires that are underinflated develop excess tread wear on the tire shoulders. Overheating resulting in internal carcass damage and potential  failure are possible from flexing the tire beyond design limits. 13-81 Protector ply Bolt plies Tread reinforcing plies Tread reinforcing plies Casing outer ply Casing outer ply Tread wear on an overinflated radial tire Tread wear on an underinflated radial tire Tread wear on an overinflated bias tire Tread wear on an underinflated bias tire