The ply rating of an aircraft tyre is used to identify the maximum static rated load capacity and corresponding inflation pressire applicable to specific operational requirements.
The ply rating is an index of tyre strength and does not necessarily correspond to the actual number of casing plies within that tyre.
The speed rating denotes the maximum rated ground speed in miles per hour to which the tyre has been tested and approved.
The load rating denotes the maximum static rated load capability of the tyre in lbs.
The inflation pressure in the data tables are taken with the tyre at ambient temperature and do not include any increase in pressure due to aircraft operation. For loads less than the maximum, the inflation pressure may be reduced accordingly as described in aircraft maintenance manuals.