Mechanical vs Electronic TPMS: A Practical Comparison Mechanical indicator caps and electronic sensors answer different questions. How they compare on accuracy, life, cost structure and use case.

Two products that answer different questions

There are two ways to know that a tyre is losing pressure. One is a device that shows you a pressure when you look at it. The other is a system that measures continuously and tells you when something is wrong.

Mechanical indicators and electronic systems are often compared as if they were competing versions of the same product. They are not. They occupy different positions in the market, require different installation, and answer different questions. Choosing between them is mostly about what the vehicle owner actually needs, and about who is paying for the answer.

How a mechanical indicator works

A mechanical tyre indicator is a small cap or gauge that screws onto the valve stem in place of the valve cap.

The common form is a coloured cap: a spring-loaded piston or a diaphragm moves as pressure falls, and a window changes colour — typically green for a reasonable pressure, yellow for a warning band, red for low. A more literal form is a small mechanical gauge that shows an actual pressure reading on a dial when the vehicle is stationary.

What the mechanical approach does well:

• It is simple. There is no battery, no radio, no pairing and no software.
• It is visible at a glance. A walk-around shows whether a tyre is in the warning band.
• It needs no installation beyond screwing it on.
• It is inherently low cost, both to make and to buy.

What it cannot do: measure temperature, record history, alarm while the vehicle is moving, report to a fleet system, or distinguish between a tyre sitting at the bottom of a normal band and one that has just started losing air.

What electronic sensing adds

An electronic TPMS sensor is mounted on or in the wheel, measures pressure and temperature with a sensing element, and transmits the values over a radio link.

The capabilities this unlocks are the reason the category exists:

• Continuous monitoring, including while the vehicle is moving — which is when a slow puncture usually becomes a failure.
• Temperature, often the more useful signal on a loaded vehicle.
• Alarms with thresholds, configurable rather than fixed by a spring.
• History and logging, where a fleet platform or an app stores readings over time.
• Central visibility, so a depot sees every vehicle rather than whoever walked past.

The cost is complexity: a battery to manage, a radio link that has to be adequate for the mounting position, and software that has to behave sensibly.

Accuracy and life compared

It is tempting to compare the two on accuracy, but they do not measure in the same way.

Aspect	Mechanical indicator	Electronic sensor
Reading	Pressure only, in bands or on a dial	Pressure and temperature, continuously
Accuracy	Limited by the spring and the mechanism; a band, not a value	Depends on calibration of each unit
Drift	The mechanism ages and readings shift	Calibrated per unit; battery is the finite life
Life	Physical wear, no battery	Coin cell on most builds; replaceable on our platform
While moving	No reading possible	Continuous
Integration	None	App, display or CAN bus

Two practical points. A mechanical cap gives a band indication, which is enough to prompt a check but not enough to log or to alarm. Its accuracy is also affected by the environment it lives in: water, grit and temperature all act on the mechanism.

On the electronic side, the honest engineering statement is that accuracy depends on calibration. Every BPU100 sensor is pressure-calibrated on our own test software before it ships, which is what makes a per-unit accuracy statement meaningful. A sensor that is not calibrated individually can only be described as a tolerance.

Cost structure, without numbers

Comparing purchase cost alone gets the decision wrong, because the two products are bought from different budgets and consumed differently.

Mechanical caps are a consumable. They are bought in packs, fitted by the owner, and replaced when they age or break. The unit cost is low and recurring, and the decision is made at the shelf.

Electronic systems are a product with a development and support tail. The sensor is the visible part; the app, the fitting method, the support process and the packaging are all part of the cost of delivering it. The buyer is usually a distributor, an OEM or a fleet, and the decision is made in a purchasing process rather than at a counter.

Where a mechanical cap tells you little, an electronic system can replace a workshop visit, catch a slow leak while moving, and produce a record. On a fleet, that trade is usually settled by the cost of one avoidable roadside failure rather than by the unit difference.

Choosing by application

Situation	Sensible choice
Owner checks tyres weekly and wants a visual prompt	Mechanical indicator
Motorcycle or scooter rider wanting live pressure	Electronic, BLE to a phone
Fleet needing central visibility and history	Electronic, with receiver or telematics
High-value tyres under heavy loads	Electronic; temperature matters as much as pressure
Low-cost accessory for a retail shelf	Mechanical, or an entry electronic kit depending on brand position
Rental or shared vehicles	Electronic with a visible alarm, not a phone-only interface

Two cases deserve a longer look. On a motorcycle or scooter, the rider is the person who checks the tyres, and the phone is already there — BLE sensing for motorcycles fits that pattern cleanly, while a mechanical cap remains a reasonable low-cost accessory for the same customer. On a passenger car or low-speed four-wheeler, the BPU140 variant is the platform our car-oriented programmes start from, and it exists because car rims and vehicle classes differ from two-wheelers in exactly the mechanical details that a mechanical cap conveniently ignores.

The honest summary

A mechanical indicator answers "is this tyre roughly right, right now, when I look at it". An electronic system answers "what is this tyre doing, continuously, and who needs to know".

Neither answer is right in every case. A retailer selling accessories in volume will make money from the first. A distributor building a brand, or a fleet managing failures, will need the second. And a range can carry both without conflict, because they are bought by different people for different reasons.

If you are unsure which one your market wants, describe the customer rather than the product: who checks the tyres, how often, and what happens when a tyre is missed. That description usually points to one answer. Our BPU100 platform is the electronic side of that answer for two- and three-wheel vehicles, and the supplier page explains how we scope a programme around it.