To insure that all components of new design haulage vehicles can function to produce the daily work requirement, it is necessary to consider the specification limits of these parts. Tires have a specification limit called ton-mile/hour (tmph). The use of this tmph tool as well as the Tire & Rim Association load tables, in the initial design of new vehicles, is important to make sure that the tire's structural limits are not exceeded.
The use of job tmph requirements in the field as a basis for tire selection will make certain that downtime due to tire heat problems will be minimal.
There are limits in both load and speed for the use of the tmph concept which must be considered as well as the conditions of ambient temperature.
The SAE has recognized the use of tmph ratings, and will publish tire test standards and recommendations in the SAE Handbook.