Pressure is part of the load chart
A reach stacker picks a loaded container out at the side, holds it out on a telescopic boom, and then travels with it. The front axle carries most of that load, and the load chart behind the windscreen assumes the tires underneath are at the pressure it was written for. Under-inflation on a machine with that much overhang does not only wear a tire. It changes the effective height and stiffness of the front axle, which changes how the machine behaves when the boom is extended and the load is high.
That is why TPMS on this class of equipment is usually sold to a safety or maintenance committee rather than to a purchasing department. A truck with a soft tire loses fuel. A reach stacker with a soft tire loses margin on a stability calculation.
What a reach stacker does to a tire
Four load cases define the duty.
- Point load. Two tires on a short front axle absorb the container, the boom and the counterweight, all of it in a narrow contact patch.
- Speed. Unlike a rubber-tyred gantry crane, a reach stacker moves at real yard speeds, so casings heat up on every long run down a block.
- Scrub. Tight turns under load grind tread off. Pressure that is too low multiplies the damage, because the sidewall flexes as it scrubs.
- Mixed fitments. Some units run wide single tires, others add a second pair of wheels on the front axle. In both cases there is a wheel that is easy to forget.
The tires nobody checks
Container handlers are usually checked on a weekly walk-round. The front near-side gets attention because it is right in front of the operator. The rear axle gets attention when somebody remembers. What gets almost none is the second wheel on a paired front axle, and any wheel hidden behind a fender or a lifting frame.
Field experience across vehicle classes says the same thing: the tire that fails is rarely the tire that was checked. TPMS changes the question from "did anyone check" to "is any wheel out of band right now", and it answers it for every wheel position on the machine, not just the reachable ones.
There is a second benefit that matters in a busy yard. A manual check tells you the pressure at the moment somebody walked past. A sensor tells you what happened overnight, during the shift the machine was working hardest, and after the last tire change.
Retrofit is usually the practical path
Yards rarely run one model. A typical terminal might have reach stackers, empty container handlers, a terminal tractor fleet, and a couple of older units from a brand nobody buys any more. Retrofit fits that reality for three reasons:
1. It does not need the OEM. No firmware change on their side, no waiting for the next production slot.
2. The bill of materials is small. Sensors, one receiver, cable, and optionally a display. That makes a single-machine trial affordable.
3. It can be standardised. If the same sensor and receiver work across models, spare parts and training stay the same as the fleet changes.
The constraints are the same as any retrofit: a mounting position on the rim or valve stem, a route for the cable and antenna, a supply in the cab or the electrical cabinet, and a decision about where the data finally goes.
Mounting and battery life
Two sensor styles cover most handler fitments. A valve-stem sensor installs in minutes and is the obvious choice where the stem is healthy and accessible. A rim-mounted sensor is the better answer where the stem is being replaced anyway, where the wheel is damaged in service, or where a fitter with a torque wrench is already on site.
Battery life is the number to check before you commit to a five-year plan. Our external sensor uses a replaceable CR1632 and is rated for at least two years; the internal sensor is rated for at least five to six years. For a yard that does not want to open wheels twice a year, that difference decides the specification. Both are IP68, which matters in a washdown environment, and the external sensor is rated from −20 to +85 °C while the internal one covers −40 to +125 °C.
Display, integration, or both
There are two places the data can go, and they are not exclusive.
A cab display is the fastest route to value. It shows per-wheel pressure and temperature, sounds an alarm, and needs no change to the machine's electronics. For a handler with no telematics and no maintenance software, this is the whole project.
Integration is for yards that already collect machine data. Our receiver outputs CAN 2.0B at 250 kbps by default with a 500 ms data period, both software-configurable, and the same platform covers J1939, RS485, RS232, Modbus RTU, PROFINET and UART. If the handler has a CAN bus, or the terminal system has a spare serial port, tire data can land where maintenance records are already kept.
Many fleets do both: display for the operator, bus output for the workshop. The receiver supports up to 256 wheel positions, so a reach stacker uses a fraction of its capacity and the same part number scales to a terminal tractor.
What to ask a supplier
1. What is the pressure accuracy? Compare a number. Ours is ±7 kPa, with tire temperature to ±3 °C.
2. What is the operating temperature range for the sensor you are quoting — internal or external type?
3. How many wheel positions does one receiver support, and what does a repeater cost if you add machines later?
4. How long does the battery last, and is it replaceable in the field?
5. Which protocols can the receiver output, and can I see a message map or DBC file?
6. What is in the delivery documentation — wheel map, alarm semantics, pinout, configuration tool?
If a supplier cannot answer the last two, assume the integration work is yours.
How we work
GZVIA designs and builds the sensor, receiver, repeater, display and cloud platform in-house in Shenzhen. We supply port machinery builders under their own brand at around 600 units a year across that segment, and we have instrumented machines that test the limits of the radio link — including a 160-wheel beam carrier delivered in ten units.
Send us the wheel count, the supply voltage and the system that has to receive the data, and we will come back with a configuration and the protocol documents.
Read more on TPMS for port machinery, see the reach stacker installation, or send us the machine details.