Resources / Technology
Internal TPMS Sensor Fitting: Band, Rim Well, and What Can Go Wrong
· 6 min read
An internal sensor is a fitting job, not a sensor job
An external sensor clamps to the valve stem: the tyre stays on, the job takes minutes. An internal
sensor goes inside the tyre, strapped to the rim well — so the tyre comes off, and the band has
to be right before that happens.
The sequence, in the order that avoids a second tyre removal:
1. Measure the rim well circumference (not the tyre, not the nominal rim diameter).
2. Cut the band to that circumference — 1650 mm covers most truck and bus wheels; larger rims
are made to the measured circumference, and it is a cutting step, not a development.
3. Fit the band into the well with the sensor body positioned where the valve hole is not.
4. Balance check, then the tyre goes back on.
5. Pair the sensor to its wheel position and write the position on the vehicle file.
The three failures we see first time
| Failure | What it looks like | Cause |
|---|---|---|
| Band too long | The sensor does not sit flat; the band loops past the well | Band cut to the old tyre rather than the rim well |
| Sensor against the valve | Fitting is awkward, the tyre bead fights the sensor body | Position chosen without looking at the valve hole |
| Wrong wheel position recorded | The app reports the right pressure under the wrong wheel | Position written from memory, not from the fitting order |
None of these is a sensor fault. All three are cheap to prevent and expensive to discover after the
tyre is back on.
Where the band sits, and why it matters
The band goes into the well — the deepest part of the rim profile, where the tyre bead sits
during fitting. A sensor strapped anywhere else changes the tyre's seating and can be crushed by the
bead. On a split rim the well can be narrow; that is the measurement to take before ordering.
Internal or external: the decision, not the specification
- External — no tyre removal, visible, replaceable without demounting. Good where the wheel is
easy to reach and a valve-mounted body is acceptable.
- Internal — protected from impact and theft, and the only option when a valve stem cannot be
used (very high pressure, unusual valves, or where the sensor would be exposed).
Both report the same pressure and temperature to the same receiver; the difference is the fitting
job and the protection, not the data.
What we will not claim
We will not give a fitment guarantee from a rim size alone. Send the rim well measurement, or the
rim drawing, and we will confirm band length — **the circumference is what decides, not the diameter
printed on the tyre**.
FAQ
Can the band be reused when the tyre is changed? The band stays on the rim; the sensor can be
re-paired if its ID has been recorded. Record the position and the ID at fitting time, or that
information is lost with the tyre.
Do internal sensors need a different receiver? No — same 433.92 MHz receiver, same wheel map.
What band length for a 22.5-inch truck wheel? Measure the rim well; 1650 mm covers most truck
and bus wheels, larger rims are cut to the measured circumference.
Does the sensor affect balancing? It is a small mass at the rim, so it is included in the
balance check like any other rim-mounted weight.
Batch assembly and fitting
What this shows: the internal sensors as they come off assembly, then the band going into the rim well - measure the well before the tyre comes off.