Unlike typical passenger car tires, OTR tires are subjected to heavier loads, continuous operations and challenging operating conditions. This demands a way to measure, benchmark and compare the OTR tires. The abbreviation TKPH & TMPH stands for Ton-Kilometer-Per-Hour and stands for Ton-Miles-Per-Hour. Calculation for both terms are same except the distance is considered in Kilometers in TKPH and in miles for TMPH.

Formula for TKPH and TMPH

The simplest calculation is as below:

TKPH = Average Load per tire x Average Kilometer covered per hour
TMPH = Average Load per tire x Average Miles covered per hour

Let’s look at the above calculation in detail:
Average Load per tire = (Q Loaded + Q Empty)/2
– Q loaded is the average weight per tire of loaded vehicle
– Q Empty is the average weight per tire when the vehicle is not loaded.

Average Kilometer Covered Per hour = N X L / H
– N is the number of trips per day
– L is the distance covered per trip (to and fro) (in Kilometers for TKPH and in Miles for TMPH)
– H is the number of operating hours per day

So TKPH can be rewritten as [(Q loaded + Q empty) / 2] x [(N x L) / H]

Why it is relevant for OTR tires?

Every tire generates heat whenever it is on a moving wheel due to flexing). When the
heat dissipation of the tire is lower than internal heat generation, the temperature inside the tire increases steadily and can reach levels potentially harmful to the rubber and other tire components, which may reduce tire life or even result in premature tire failure. Choosing the correct tire specification with the most appropriate TKPH rating for site operations can significantly improve tire life and reduce vehicle operational costs

Higher TKPH rated tire = Higher Heat Resistance (better for long haul cycles) and Lower Wear Resistance (bad for worn out tire life).
Lower TKPH rated tire = Lower Heat Resistance (bad for long haul cycles) and Higher Wear Resistance (good for worn out tire life).

While selecting, the tire’s TKPH value according to the technical datasheet must be higher than the calculated TKPH value according to the duty cycles. Otherwise the tire will be unsuitable.