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How to Calculate TKPH
What is TKPH?
TKPH expresses the relationship between tyre load, distance travelled and operating time. It helps assess the workload placed on a tyre in relation to its ability to manage heat.
Two values matter when selecting a tyre:
- Operating TKPH: the workload you calculate from your site’s tyre loads and average work-shift speed.
- Tyre TKPH rating: the working capacity specified for a particular tyre under defined conditions.
A tyre’s TKPH rating depends on its design, including its size, type and rubber compound. The operating calculation, meanwhile, uses the load carried by each tyre and the distance covered during the working period.
TKPH does not describe the complete capability of your vehicle. You still need to consider the machine’s requirements, tyre size, terrain and other operating conditions when selecting a suitable specification.
The importance of TKPH.
Choosing the right OTR tyre helps protect tyre life and manage operating costs. This is particularly relevant for mining and earthmoving tyres, where repeated haul cycles combine substantial loads with distance and speed.
A tyre that cannot accommodate the operating workload may experience excessive heat build-up. That can contribute to premature deterioration, tyre damage and unplanned downtime.
A TKPH calculation helps you assess whether the tyre specification matches the work. However, calculating TKPH correctly does not guarantee a particular tyre lifespan. Inflation pressure, loading practices, road conditions and maintenance also affect performance.
Use TKPH as part of a wider tyre selection process, supported by accurate operating data and technical advice.
The TKPH formula.
The basic formula for calculating operating TKPH is:
Operating TKPH = mean tyre load × average work-shift speed
Use the following units:
| Input | Required unit |
|---|---|
| Mean tyre load | Tonnes per tyre |
| Average work-shift speed | Kilometres per hour |
| Result | TKPH |
You calculate the two inputs separately before multiplying them together.
Step 1: Calculate mean tyre load
Mean tyre load is the average of the load carried by a tyre when the vehicle is empty and when it is fully loaded.
Mean tyre load = (tyre load empty + tyre load fully loaded) ÷ 2
Use the load on the tyre being assessed, rather than the total vehicle weight or payload alone. The calculation needs to reflect the load that tyre actually carries.
For example, if a tyre carries 9,000 kg on an empty vehicle and 15,000 kg on a loaded vehicle:
Mean tyre load = (9,000 + 15,000) ÷ 2 = 12,000 kg
Convert kilograms to tonnes before using this value in the TKPH formula:
12,000 kg ÷ 1,000 = 12 tonnes
Keeping the units consistent is essential. Entering 12,000 instead of 12 in the final formula would produce an incorrect result.
Step 2: Calculate average work-shift speed
Average work-shift speed reflects the distance covered over the operating period. It is different from the vehicle’s maximum speed or its speed on one part of the route.
First, establish the round-trip distance. This is one complete cycle, such as travelling from the loading point to the unloading point and returning to the starting point.
Next, multiply the round-trip distance by the number of completed cycles. Divide that distance 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
Use the same operating period for the cycle count and hours. When collecting site data, confirm the applicable treatment of breaks and shift changes with your technical adviser.
Step 3: Calculate operating TKPH
Multiply the mean tyre load by the average work-shift speed:
Operating TKPH = 12 tonnes × 26.25 km/h = 315 TKPH
You now have an operating workload to compare with the tyre’s applicable TKPH rating.
TKPH calculation example.
The following example brings all the inputs and calculations together.
| Operating input | Value |
|---|---|
| Load per tyre when the vehicle is empty | 9,000 kg |
| Load per tyre 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 tyre load
(9,000 kg + 15,000 kg) ÷ 2 = 12,000 kg = 12 tonnes
2. Average work-shift speed
(14 km × 15 cycles) ÷ 8 hours = 26.25 km/h
3. Operating TKPH
12 tonnes × 26.25 km/h = 315 TKPH
For these inputs, the calculated operating TKPH is 315. This describes the workload in the example; it is not a universal recommendation for a machine, tyre size or application.
Operating TKPH and tyre TKPH rating.
Once you have calculated operating TKPH, compare it with the rated TKPH for the exact tyre specification under consideration.
The calculated operating TKPH must remain below the tyre’s applicable rated TKPH.
Do not compare the result with the tyre’s load index. Load index and TKPH describe different characteristics, so one cannot substitute for the other.
Check that the rating applies to the correct tyre size and compound. Operating conditions also matter: Magna’s TKPH guidance references a standard ambient temperature of 38°C. Different temperatures or operating conditions may require a revised assessment.
Where possible, use data from several representative operating periods rather than relying on a single cycle or an unusually quiet shift. If routes, loads or shift patterns change, review the calculation.
For more background, read our guide to TKPH and the compound of OTR tyres. You can also learn how to read extra tyre markings.
Higher and lower TKPH ratings.
In general, a higher TKPH rating indicates greater capability to manage the heat associated with demanding haul cycles. A lower TKPH compound may offer a different balance, with greater emphasis on cut and wear resistance.
This is why the highest rating is not automatically the best choice for every operation. The aim is to match heat resistance and wear characteristics to the actual workload and ground conditions.
The same principle applies when selecting giant tyres for large mining equipment. Tyre dimensions alone do not confirm that a particular compound suits your haul cycle.
Discuss the calculated operating TKPH alongside the machine, load, route, tyre size and site conditions before choosing a specification.
TKPH and TMPH.
TKPH and TMPH both describe tyre workload, but they use different unit systems.
TKPH uses metric tonnes and kilometres per hour. TMPH expresses workload using tons and miles per hour. Check the precise unit definitions in the manufacturer’s technical documentation before calculating or converting values.
If your site records distance in miles or load in pounds, convert the inputs to the units required by your calculation. A value in TMPH cannot be compared directly with a rating in TKPH.