What changes when a dual pair becomes one tyre
A city bus is often specified with wide-base single tyres (also called super singles) instead of
the conventional dual pair on the rear axle. One tyre does the work of two, so:
- The number of monitored positions halves on that axle — six wheels instead of eight on a
6-wheel bus, four instead of six on some low-floor layouts.
- Each tyre carries a different load than it did as part of a pair, so the target pressure is a
different number, not the old one divided in two.
- A pressure loss is a bigger event. In a dual pair the healthy tyre of the pair partially
compensates; a single wide tyre has no partner. The bus does not "lean onto the other one".
That is the whole case for monitoring a wide-base bus more tightly than a conventional one.
What we tested
A city bus on wide-base tyres, 433.92 MHz sensors on the wheels, receiver on the vehicle bus. The
short clip shows the setup running:
What the test is looking for is not a spectacular number. It is the boring thing an operator needs:
**does every wheel keep reporting while the bus is moving, with the tyres at operating pressure and
temperature, and does a pressure change show up before it becomes a roadside stop.**
The pressure range question
Bus tyres on wide-base wheels typically run in the 0.8–0.95 MPa (8–9.5 bar) region, higher than
a passenger car and lower than OTR. Our industrial range is **0–1400 kPa gauge (100–1500 kPa
absolute) at ±7 kPa**, so the operating point sits comfortably inside the range rather than at the
top of it.
Two things we state plainly instead of hiding:
- Gauge is the number we quote. 0–1400 kPa gauge; the absolute figure is in brackets because
some test benches report it that way. Mixing the two produces a 100 kPa-looking error that is
actually a unit error.
- Temperature matters as much as pressure on a bus. Brake heat and continuous stop-start work
raise the tyre temperature; the sensor reports temperature alongside pressure for exactly this
reason.
Wheel map for a wide-base bus
A 6-wheel bus with wide-base rear tyres is 4 positions, not 6:
| Position | Typical name on the sheet |
|---|---|
| Front left | 11 |
| Front right | 12 |
| Rear left | 21 |
| Rear right | 22 |
If the bus keeps dual tyres on the rear axle, it is 6 positions and the inner tyre needs its own
sensor — a detail that is usually missed until the first installation day.
Installation notes specific to buses
1. Receiver near the rear axle, not behind the dashboard, where the bus builder's harness ends.
The last wheels are usually the ones that suffer.
2. The band length is cut to the rim circumference. 1650 mm covers most truck and bus wheels;
larger rims are made to the measured circumference — it is a cutting step, not a development.
3. Pairing is recorded per position, and the record belongs on the vehicle file, not in
somebody's phone.
4. Do not fit the display where the driver has to look down at it. A bus driver has enough to do.
FAQ
Do wide-base tyres need a different sensor? No — same sensor, different pressure target and a
different wheel map. The sensor range covers the operating pressure with margin.
How many sensors on a 6-wheel wide-base bus? Four. The dual pair became one tyre, so the inner
position no longer exists.
Can the same receiver handle buses and trucks? Yes: one receiver addresses up to 256 wheel
positions, and one interface is fitted per receiver at build (CAN 2.0B, RS485/Modbus RTU slave,
RS232/UART, or PROFINET via a gateway).
What is the point if the bus is checked at the depot every morning? The morning check is a
snapshot by hand. Monitoring catches the tyre that loses pressure during the shift — which is the
one that stops the bus on the route.