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How to Calculate TKPH
What is TKPH?
TKPH expresses the relationship between tire load, distance traveled and operating time. It helps assess a tire’s workload in relation to its ability to manage heat.
When selecting a tire, distinguish between two values:
- Operating TKPH: the workload calculated from your site’s tire loads and average work-shift speed.
- Tire TKPH rating: the working capacity specified for a particular tire under defined conditions.
The tire’s rating depends on its design, including its size, type and rubber compound. The operating calculation uses the load carried by each tire and the distance covered during the working period.
TKPH does not describe the complete capability of the vehicle. Machine requirements, tire size, terrain and other operating conditions remain part of the selection process.
The importance of TKPH.
Choosing the right OTR tire helps protect tire life and manage operating costs. For mining and earthmoving tires, repeated haul cycles place demands on the tire through a combination of load, speed and distance.
If the operating workload exceeds the tire’s capability, excessive heat can contribute to premature deterioration, tire damage and unplanned downtime.
Calculating TKPH helps you assess the relationship between the work and the tire specification. It does not guarantee a particular service life. Tire pressure, loading practices, road conditions and maintenance also influence performance.
Use TKPH alongside the other technical requirements of your equipment and operation. Accurate site data gives your tire adviser a stronger basis for recommending an appropriate specification.
The TKPH formula.
Use this formula to calculate operating TKPH:
Operating TKPH = mean tire load × average work-shift speed
Keep the inputs in the correct units:
| Input | Required unit |
|---|---|
| Mean tire load | Metric tons per tire |
| Average work-shift speed | Kilometers per hour |
| Result | TKPH |
In the United States, site records may use pounds, U.S. tons and miles. Convert those records before using them in a TKPH calculation. A U.S. ton and a metric ton are different units.
Calculate the mean tire load and average work-shift speed separately, then multiply the results.
Step 1: Calculate mean tire load
Mean tire load is the average of the load carried by a tire when the vehicle is empty and when it is fully loaded.
Mean tire load = (tire load empty + tire load fully loaded) ÷ 2
Use the load carried by the tire being assessed. The total vehicle weight or payload alone does not tell you how much load that individual tire carries.
For example, suppose the load per tire is 9,000 kg when the vehicle is empty and 15,000 kg when it is loaded:
Mean tire load = (9,000 + 15,000) ÷ 2 = 12,000 kg
Convert this result to metric tons:
12,000 kg ÷ 1,000 = 12 metric tons
Use 12 in the final TKPH formula, rather than 12,000. Keeping kilograms and metric tons separate prevents a significant calculation error.
Step 2: Calculate average work-shift speed
Average work-shift speed describes the distance covered over the operating period. It is not the truck’s maximum speed or its speed during one section of a haul.
Start with the distance of one complete round trip. For a hauling operation, this includes the trip from the loading point to the unloading point and the return to the starting point.
Multiply the round-trip distance by the number of completed cycles. Then divide by the hours in the operating period.
Average work-shift speed = (round-trip distance × number of cycles per shift) ÷ total hours of operation per shift
For example:
Average work-shift speed = (14 km × 15 cycles) ÷ 8 hours = 26.25 km/h
Make sure the cycle count and operating hours cover the same period. Confirm how to account for breaks and shift changes with your technical adviser when collecting site data.
Step 3: Calculate operating TKPH
Multiply the two results:
Operating TKPH = 12 metric tons × 26.25 km/h = 315 TKPH
The result gives you an operating workload to compare with the tire’s applicable TKPH rating.
TKPH calculation example.
This example uses metric units throughout to show how the TKPH calculation works.
| Operating input | Value |
|---|---|
| Load per tire when the vehicle is empty | 9,000 kg |
| Load per tire when the vehicle is loaded | 15,000 kg |
| Operating hours per day | 8 hours |
| Number of cycles per day | 15 |
| Round-trip distance per cycle | 14 km |
1. Mean tire load
(9,000 kg + 15,000 kg) ÷ 2 = 12,000 kg = 12 metric tons
2. Average work-shift speed
(14 km × 15 cycles) ÷ 8 hours = 26.25 km/h
3. Operating TKPH
12 metric tons × 26.25 km/h = 315 TKPH
For these operating inputs, the result is 315 TKPH. This is an example workload, not a tire recommendation for a specific truck, tire size or site.
If your records use pounds and miles, convert the inputs before following these steps. Do not mix metric and U.S. customary units within the calculation.
Operating TKPH and tire TKPH rating.
Compare your calculated operating TKPH with the rated TKPH for the exact tire specification you plan to use.
The calculated operating TKPH must remain below the tire’s applicable rated TKPH.
The comparison is with the tire’s TKPH rating, not its load index. Load index and TKPH describe different tire characteristics and cannot replace each other.
Check the rating for the correct tire size and compound. You also need to account for the conditions under which the rating applies. Magna’s TKPH guidance references a standard ambient temperature of 38°C, approximately 100°F. Other temperatures or operating conditions may require a revised assessment.
Use data from several representative operating periods where possible. A single light-load shift may not reflect the demands of the wider operation. Review the calculation when routes, loads or shift patterns change.
For more detail, read about TKPH and the compound of OTR tires. Our guide to reading extra tire markings explains other tire information.
Higher and lower TKPH ratings.
A higher TKPH rating generally indicates greater capability to manage the heat associated with demanding haul cycles. A lower TKPH compound may provide a different balance, with greater emphasis on cut and wear resistance.
Selecting the highest rating is not automatically the right approach. The goal is to match the tire’s heat resistance and wear characteristics to the work and ground conditions.
This also matters when selecting giant tires for large mining equipment. Size alone does not confirm whether the tire’s compound suits the intended haul cycle.
Assess the operating TKPH together with the machine, tire size, load, route and site conditions. This helps keep the selection focused on the demands of your operation.
TKPH and TMPH.
U.S. tire specifications may also list TMPH, or Ton-Miles per Hour. TKPH and TMPH both describe tire workload, but they use different unit systems.
TKPH uses metric tons and kilometers per hour. TMPH uses tons and miles per hour. Confirm the precise definition of “ton” in the manufacturer’s documentation before calculating or converting a value.
Do not compare an operating result in TKPH directly with a tire rating in TMPH. Bring both values into the same unit system first, using the manufacturer’s technical guidance.
Keeping units consistent is especially important when your fleet records loads and distances in U.S. customary units while the tire documentation lists metric ratings.