Equipment World Digital Magazine
Issue link: https://read.dmtmag.com/i/873881
these mega tires don't overheat, but the engineering concepts behind TMPH can be useful for any con- tractor wanting to get the full value of his tires and avoid downtime. The formula for tires is easy to compute. TMPH = Load x Speed. Simply put, the heavier the load, the slower you need to go. And if you want your trucks to go faster, adjust the load downward. "There is a TMPH figure for the tire and a TMPH number for the site," says Seibert. For the tire, the primary determining factors for its TMPH are the size, design and rub- ber compound. That sets the limits a tire can handle as far as load and speed. For the site, it's the actual measurements for how far your trucks will be carrying the load. To avoid overheating, the TMPH figure for the tire should match the TMPH figures for the site. The number of curves and eleva- tions on the site can also affect heat and TMPH site calculations, says Gary Pompo, manager field techni- cal services, BKT Tires. Load and torque from climbing or descending grades create tire deflection, which leads to heat generation within the tire. Speed determines how fast this deflection is repeated. When the combination of deflection and speed adds heat faster than the tire gives up heat to the air, the tire overheats. If the worksite parameters change – such as the slope, length of grades, number and radius of curves, or haul distances – the worksite TMPH should be recalculated, says Pompo. (The engineering standard for this is SAE J1098.) In some cases that may mean changing to tires with different rubber compounds or designs. If the numbers still don't add up, the site may need to be reconfigured. "It is important to understand that TMPH is not the only thing that September 2017 | EquipmentWorld.com 28 maintenance | continued Wheel loaders have a 60-40 weight distribution with a full bucket. Tire rotation can extend the life of the set. Check air pressure weekly. Write it down and track it over time so you can discover small problems before they get big.