A pit is not a highway with bigger tires
An off-the-road tire on a haul truck carries the weight of a small building at walking speed, in dust and heat. On a highway vehicle, tire pressure is mostly a fuel and wear question. In a pit it is a casing-life and uptime question: an underinflated OTR tire fails by heat separation long before it looks flat, and a truck stopped on a ramp blocks the whole cycle.
Monitoring it is a different specification in four places: the pressure range, the number of wheel positions, the radio path, and how the sensor is mounted.
The pressure range starts at 9 bar
Mine tires are inflated hard. Cold inflation pressure on large OTR tires commonly sits at 9 bar, roughly 130 psi, and the biggest sizes go higher.
Two consequences follow.
Put the working point inside the span, not at the top of it. Pressure rises with temperature during a shift, and a sensor that is already near its ceiling has nowhere to go. The pressure range should be specified from the tire data book plus that rise, with headroom left over.
Absolute accuracy has to be read in context. Our receivers are specified at ±7 kPa. Against a 9 bar working pressure that is a small fraction of the reading, so the honest comparison is against the tolerance your tire book states, in the same unit — bar or psi — so nobody converts a figure and loses the meaning.
Then ask what the system does above its span. On a mine tire the wrong answer is a plausible-looking number near full scale. The right answer is an over-range indication the controller can see.
Wheel count on mine equipment
A rigid haul truck carries four or six tires. Add a trailer, or work with the multi-axle heavy haulage units used on some sites, and a single machine can present 22 to 48 wheel positions.
That sounds like a capacity problem, and it is not. One receiver addresses up to 256 wheel positions, so on almost every mining machine the receiver count is set by radio coverage rather than by wheel count. The multi-axle layout page goes deeper; the rule is the same everywhere: size the system on the drawing of the machine, not on a category name.
The body is the radio problem
A haul truck is a large steel box that changes shape as it works. The raised dump bed is a wall between the front and rear wheel groups, and it moves. The radio link at 433.92 MHz therefore changes during the cycle: a sensor that reads perfectly on the bench may drop out with the bed raised, on the loaded leg of the haul.
In practice this means:
- Plan repeaters per blocked span, not per axle. A repeater covers the wheel positions the receiver cannot hear from where it is mounted.
- Mount the repeater on the chassis, not on the moving bed, and route its cable so the articulation has somewhere to go. Repeaters rated IP68 and supplied from DC 10–30 V can be mounted where the geometry needs them.
- Survey the machine in its working attitudes before the harness is cut, checking every wheel position with the bed down and with the bed up, then repeat the survey once the machine is loaded and doing real work.
The pit only sharpens the consequence: an intermittent wheel position is a wheel nobody watches.
Internal band-mount or external on the valve stem
This is the decision that mine operators argue about most, and it is usually a maintenance decision rather than a radio one.
External on the valve stem. Fitted in minutes without demounting the tire. The CR1632 sensor is rated from −20 to +85 °C with at least two years of life. In a pit the valve stem is exposed to rock strike, mud packing, high-pressure washdown, and in some yards to being unscrewed by hand.
Internal, fixed to the rim with a band. Rated from −40 to +125 °C with five to six years of life. Nothing is exposed to the road or to the wash, and it cannot be removed without demounting the tire. It also reads the air inside the tire cavity, the temperature that describes casing stress; an external sensor sits at the valve, where brake heat, sun and wheel wash influence the reading.
Fitting an internal sensor means the tire comes off, so align it with the tire service or rotation you already run instead of creating a separate visit. That makes the tire shop part of your project: give them a written fitting procedure, the band specification and the torque figure.
Many fleets end up mixed: internal on the haul fleet, where tires are handled on a planned schedule, and external on trailers and auxiliary units where fast service and a low entry cost matter more.
Temperature, dust and washdown
Mine conditions punish the outside of a sensor:
- Bench heat and direct sun, then cold nights at altitude. The internal sensor's −40 to +125 °C range covers that; the external sensor's −20 to +85 °C is a genuine limit.
- Dust and fines that pack around a stem and hold moisture there.
- High-pressure washdown, which the IP68 sensor and receiver tolerate, and the IP65 display does not enjoy at close range.
Two habits keep sensors alive: keep the wash jet off the valve stem and cable entries, and re-check the seal on any wheel that has just been through a tire change.
What to send us
A mine configuration is quick to produce once the inputs are right. Send:
- Machine type and axle layout drawing, even a photograph of the machine
- Tire size, and the cold inflation pressure in bar or psi
- Wheel position list, with any position you already know is hard to reach
- Ambient range and washdown regime
- Which controller or fleet system will read the data, or whether a display is enough
- Whether tires are serviced on site or by a contractor
We return a sensor count with the internal and external split per axle, a receiver count, a repeater plan with mounting points, the interface for your controller, and a wheel map template.
How we work
GZVIA develops sensors, receivers, repeaters, displays and the cloud platform in Shenzhen. A receiver addresses up to 256 wheel positions, pressure accuracy is ±7 kPa, the sensors use Infineon chips and are rated IP68, and the same platform speaks CAN 2.0B, J1939, RS485, RS232, Modbus, PROFINET and UART.
If you are specifying for a mine fleet, start from TPMS for mining, check the CAN bus integration route, or send the machine and tire details. Contact us here.