Why OTR tire pressure monitoring is a different problem
OTR tire pressure monitoring on a mining truck is not the passenger-car problem at a larger scale.
A car tyre fails because it is worn or punctured; a haul-truck tyre usually fails because it ran at the
wrong pressure for hours. Under-inflation on a 2-metre tyre does not look flat — it looks normal, and
it destroys the casing from the inside.
The economics make the case on their own. A single large OTR tyre costs far more than a set of sensors,
and a casing destroyed by heat cannot be repaired. The failure is also dangerous: a sudden loss on a
loaded haul truck is a machine-stopping event at best.
So the goal is not "display the pressure". It is detect the drift before the heat builds up — which
is a data problem: per-wheel pressure and temperature, reliably reported, with an alarm that means
something.
What the sensing chain looks like
| Stage | What it is |
|---|---|
| Sensor | One per wheel position, 433.92 MHz, battery powered, measuring pressure and temperature |
| Receiver | One unit on the machine, up to 256 wheel positions |
| Output | One interface: CAN 2.0B (11-bit or 29-bit), RS232, RS485 or Modbus RTU — chosen at the factory, one per unit |
| Consumer | Truck controller, cabin display, or a gateway to the mine network |
Two numbers matter to an engineer planning this:
- Pressure range: 0–1400 kPa gauge (100–1500 kPa absolute), accuracy ±7 kPa. Note the two figures;
the gauge value is what a tyre gauge reads, the absolute value is what the sensor sees.
- Data period: 500 ms on the output side. Faster does not help a tyre; slower starts to miss the
shape of a leak.
Temperature range is −40 to +125 °C for the internal sensor (external is −20 to +85 °C), and the
433.92 MHz sensor is IP68 — a haul road is dust, water and washing.
Which sensor fits which rim — the question that decides the project
This is where OTR projects stall, because a mining wheel is not a car wheel:
| Rim / installation | Sensor that fits | Practical note |
|---|---|---|
| Multi-piece OTR rim with a large valve stem | External, valve-mounted plus an OTR extension | Nothing has to be dismantled to fit it; a tyre change does not require re-pairing |
| Standard tubeless rim | External valve-mounted or internal band-mounted | The band version is protected but is only reachable when the tyre comes off |
| High-temperature duty (near brakes, hot ambient) | Internal valve type | Rated to +125 °C for exactly this case |
The band is the part people get wrong in a different way: it is a steel band around the rim well.
The length is cut to your rim circumference. **1650 mm covers what most truck and bus wheels need; we
have also supplied 2500 mm where the wheel was larger** — and the length is a cutting step, not a
development, so a longer rim is not a lead-time problem.
Getting the data to where decisions are made
Three routes, and the choice is driven by what the mine already runs:
1. CAN into the truck controller. The receiver publishes the tyre set on the vehicle bus. This is the
route when a controller needs to act — derate, alarm, log — rather than a human needing to look.
We work in 11-bit standard or 29-bit extended frames, fixed per unit, and we have deployed J1939-format
message sets in construction machinery integrations with major OEMs. (We hold no J1939 conformance
certificate, and we say so rather than imply one.)
2. Modbus RTU / RS485 into a PLC. The receiver is a slave only — the PLC polls it. This is the usual
route on fixed plant and on machines with an existing control cabinet.
3. 4G to a fleet platform. A gateway publishes the values over MQTT to a broker you control, with
change-triggered uplink and local buffering when coverage drops. This is the route when the decision is
made in an office, not in the cab.
Whichever route, ask for the same three documents: **message map, scaling/byte order, wheel-position
table**. A supplier who cannot produce those is selling a box.
The radio path is the engineering risk, not the sensor count
A haul truck is a large steel body, and the tyres you care about sit under it. Two rules from site work:
- Plan the receiver and repeater positions from the drawing. Which wheels have line of sight, which do
not, and where a repeater can be mounted so it is not itself shielded.
- Do not mount the receiver behind a structural member because the cable was shorter there. This single
mistake accounts for most "the system works on one machine and not the other" stories.
On a rigid haul truck, one receiver is normally enough. On anything with a trailer, or with more than
roughly ten metres between the furthest wheel and the receiver, budget for a repeater.
What to send us to get a real answer
1. Machine type and wheel count (6×6 articulated, rigid haul truck, loader) and the tyre size.
2. Rim type — multi-piece OTR, standard tubeless, or something unusual; a photo of the valve area
settles more than a description.
3. Where the data must end up — controller, display, or platform — and which interface exists.
4. Working pressure and expected temperature, so the range can be confirmed rather than assumed.
With those four we reply with the configuration, the frame layout and the sensor choice — in writing,
before anything is ordered. If the answer is "the standard part will not do it", we say that in the first
reply rather than shipping something that reads saturated.
OTR tyre monitoring is also covered from the fleet side on mining and quarry
and from the interface side on CAN bus TPMS integration. If you are evaluating a
retrofit, send us the four answers and we will put the configuration in writing.