The short answer
Both interfaces will carry tire data across a machine without losing it. Tire pressure is a slow signal, sent a few times per second from one device, over a bus that is short by industrial standards. Either physical layer handles that comfortably.
So the decision is not "which one is technically better". It is a question about your machine:
- If the controller that needs tire data already has a CAN port, use CAN. The receiver becomes one more node and your integration work drops.
- If that controller is a PLC or HMI whose world is digital and analogue I/O, use RS485 with Modbus RTU. It needs no new hardware and every industrial controller speaks it.
- If you genuinely do not know yet, buy a receiver that offers both. The choice then stays reversible.
The CAN bus TPMS integration page covers the CAN route in detail. This article compares the two on the points that actually change a project.
How the two layers differ
CAN is a complete protocol stack defined down to the frame. RS485 is only the electrical layer; the protocol lives on top of it, usually Modbus RTU in industrial machinery. That distinction explains most of the practical differences.
CAN, briefly:
- Differential pair, multi-master; any node may transmit when the bus is free
- Arbitration by identifier, so a high-priority frame wins without being lost
- 11-bit or 29-bit identifiers, which is where CAN 2.0B fits
- Frame-level CRC, acknowledgement from receivers, automatic retransmission on error, and per-node error counters
- A receiver can detect that it has been isolated from the bus and report it
RS485, briefly:
- Differential pair as well, but no addressing, arbitration, acknowledgement or error recovery at the physical layer
- Usually single master, multiple slaves, polled in turn
- Frame integrity comes from the protocol above, for example the CRC in Modbus RTU
- No unsolicited transmission: a slave speaks only when asked
- Longer cable runs at lower speed, which suits machines where the controller sits far from the rear axles
Neither is fragile. They fail in different ways, and that is what you are really choosing between.
What that means for tire data specifically
Tire monitoring is one talker, many listeners, low rate. Our receivers use a 500 ms data cycle by default, which is two updates per second per wheel, and both interfaces deliver that with room to spare on a 250 kbps CAN bus or a 19200 baud serial line.
The differences that matter in practice come down to three things.
Who starts the conversation. On CAN the receiver transmits on its own schedule. On RS485 the PLC must ask. If your alarm strategy depends on the receiver announcing a rapid leak the moment it sees one, CAN is the more natural fit. On RS485 you get the same information, but only as fresh as your polling interval.
How failures surface. CAN reports errors at the frame level and gives each node error counters, so a marginal wiring problem appears as increasing error counts before it becomes a data outage. On RS485, a silent node is simply silent; you must implement timeouts and a heartbeat to notice. Both work, but one of them requires you to write that logic.
How much software you own. With CAN and a documented frame layout, your integration is a decoder. With Modbus you also own the polling schedule, the timeout policy and the stale-data handling. That is not difficult work, but it is work.
Bus load, latency and determinism
At 250 kbps with a 500 ms cycle, tire frames occupy a tiny fraction of the bus, even on a machine with 160 wheels distributed across several messages. There is no realistic scenario where tire data saturates a CAN bus, which is why a slower default cycle is a sensible engineering choice rather than a limitation.
Latency behaves differently on the two layers. On CAN, arbitration means the highest-priority frame gets through first, so a leak alarm can be given priority over routine pressure data. On RS485, worst-case latency is the master's scan time multiplied by the number of slaves, plus retries for any slave that fails to answer. On a PLC with a 100 ms scan and a handful of devices, that is still well inside a second. On a heavily loaded serial network it can grow, and it is worth calculating rather than assuming.
If your requirement is "the controller must see a rapid leak within a second", both meet it. If your requirement is tighter than that, you are likely specifying the wrong kind of system for tire data.
Wiring and environment
The good news is that the physical rules are almost identical, because both are differential buses:
- Twisted pair for the signal pair, plus a common conductor
- 120 ohm termination at both ends of the bus, and only at the ends
- Daisy chain topology; short stubs, never a star
- Shielding grounded at one end
- Routing away from motor and drive cables on the machine
The differences are in the speed and distance trade. CAN holds its speed over useful chassis lengths at 250 kbps. RS485 goes further at low baud rates, which is exactly what serial polling allows. On mining trucks, port equipment and long beam carriers, the cab is often far from the rear axle group, and both approaches have been used successfully.
Our receivers and repeaters are rated IP68 and run from DC 10-30 V, so they mount where the machine needs them rather than where a convenient supply happens to be.
Cost, effort and reversibility
On paper, RS485 usually wins the hardware argument: a PLC port and two wires against a CAN module and a bus segment. CAN usually wins the software argument: no polling loop to write, frame-level diagnostics for free, and priority handling when it matters.
In practice the deciding factor is often organisational. If the machine already has a CAN bus with other devices on it, adding tire data is a small change to an existing interface design. If the machine is a serial control panel with no bus at all, introducing CAN means introducing a bus, its termination, its wiring discipline and its commissioning tools for the sake of one sensor system.
That is why we put both interfaces on the same receiver. You choose the one that fits today, and if the next machine goes the other way, the part number does not change. The TR100 receiver page lists the full protocol set we support.
Five questions that settle it
1. Does the controller that needs tire data have a CAN port today, or would CAN be a new bus on this machine?
2. Is anything else already on that bus, and does it have spare bandwidth?
3. Do you need the receiver to announce an alarm immediately, or is a polled answer within your scan time enough?
4. How far is the controller from the rear axles, and at what speed will the bus run?
5. Who writes the receiving software — your team, an integrator, or nobody yet?
Answer those five and the interface usually picks itself. If the answer to the third question is "immediately" and the answer to the first is "yes", use CAN. If the machine is a serial control system and the answer to the third is "within half a second is fine", RS485 with Modbus RTU is simpler.
What we supply either way
GZVIA develops the sensor, receiver, repeater, display and cloud platform in house in Shenzhen. A single receiver supports up to 256 wheel positions, and we have delivered a 160-wheel beam carrier configured as two receivers, twelve repeaters and 160 sensors, with the largest single machine we have instrumented carrying 224 wheels across 28 axles. Pressure accuracy is ±7 kPa, and the receivers speak CAN 2.0B, J1939, RS485, RS232, Modbus RTU, PROFINET and UART from the same hardware family.
For a CAN integration we hand over the message map or DBC file, the alarm semantics and a configuration tool. For a serial integration we add the register map. Send us the controller you are reading data into and the wheel count, and we will recommend the interface rather than the one we prefer. Tell us about the machine.