Tyre Pressure Monitor System (TPMS)

Tyre Pressure Monitor System (TPMS)

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What is a TPMS?

The purpose of the tyre pressure monitoring system (TPMS) in your vehicle is to warn you that at least one or more tyres are significantly under-inflated, possibly creating unsafe driving conditions. If the warning light comes on the driver needs to have their tyre(s) checked urgently.

However, having a TPMS on your vehicle does not mean you can stop checking your tyres, you still need to check your tyres regularly for tread depth and condition as well as air pressure. The sensors within the TPMS can fail so they do need checking regularly.

TPMS Warning Light results in an MOT Failure

In the UK, for vehicles that have TPMS fitted and for all new vehicles manufactured from 2014 and onwards, the pressure sensor system is now checked as part of your MOT and a warning light displayed on the dashboard will result in a failed MOT.

The TPMS low tyre pressure indicator is a yellow symbol that illuminates on the dashboard instrument panel in the shape of a tyre cross-section and an exclamation point as shown.

TPMS Services at Bespoke Wheels

Sensors can fail at any time but generally last for approximately 5 years. Once they fail they will need to be replaced. It is important your sensors are checked regularly to ensure they are all in good working order. It is possible that the onboard computer may not tell you if a sensor has failed so, here at Bespoke we can check your sensors for you using our Schrader Exp Air equipment. We can also ‘service’ the sensors.

If your TPMS indicator is showing, we will check your tyre condition, tread and pressures for signs of wear, damage or deflation and carry out any necessary work to ensure you are safe to drive. We can reset the onboard computer system as appropriate.

We can fit new TPMS sensors and re-programme the sensors where necessary to talk to the onboard computer system. Some vehicles will register the new sensors once the vehicle is in motion, other onboard computer systems will need re-programming. At Bespoke, we can take care of all this for you.

We can fit either an Original Equipment (OE) brand sensor or in some cases can use a Schrader easy-sensor that can be programmed to match your vehicle. We can also copy your OE sensors if you wish to run a second set of winter tyres allowing you to inter change wheels without having to switch sensors.

If you need new tyres and your sensors are in good working order, we will not need to change your existing sensors when we fit the new tyres.

If you have any queries about these sensors please call us today on 01926 88 77 22 and ask to speak to Marcus or Pete, who will be happy to help.

Why do we have TPMS and it’s history

Many accidents on our roads every year are a result of tyre related issues and TPMS is a system that can help drivers as an addition to their tyre maintenance routines. Ultimately proper tyre maintenance helps prevent accidents and TPMS can help with this. The TPMS does NOT mean you can stop checking your tyres though. You still need to check your tyres regularly for tread depth and condition as well as air pressure. And the sensors within the TPMS can fail so they need checking regularly.

In the USA and as a result of TREAD Act, most vehicles sold in the United States since 2007 include a tyre pressure monitoring system of some kind. Then the European Union made it compulsory for all cars sold in the EU after November 2014 to have a TPMS system.

A TPMS was first used in the Porsche 959 in 1986 and then other manufacturers over time started to use the system but legislation has really driven its widespread use.

How do TPMS work?

Not every TPMS works the same way. The illumination of the low tyre pressure indicator represents the final step in the process of either an indirect TPMS or a direct TPMS.

Indirect TPMS

An indirect TPMS typically relies on wheel speed sensors that the anti-lock brake system uses. These sensors measure the rate of revolution each wheel is making and can be used by on-board computer systems to compare with each other and to other vehicle operation data such as speed.

Based on the rate of revolution of each wheel, the computer can interpret the relative size of the tyres on your vehicle. When a wheel starts spinning faster than expected, the computer calculates that the tyre is underinflated and alert the driver accordingly.

Many of the BMW and Mini cars with runflat tyres used this system, but the later cars have now switched to a Direct TPMS system.

So an indirect tyre pressure monitoring system doesn’t actually measure tyre pressure. It’s not electronically processing the same kind of measurement as a tyre gauge. An indirect tyre pressure monitor simply measures how fast your tyres are rotating and sends signals to the computer that will activate the indicator light when something in the rotation seems wrong.

Advantages of Indirect TPMS

  • Relatively inexpensive compared to a direct TPMS
  • Requires less programming/maintenance over the years than a direct TPMS
  • Less overall installation maintenance than its direct counterpart

Disadvantages of Indirect TPMS

  • May become inaccurate if you purchase a bigger or smaller tyre
  • May be unreliable when tyres are unevenly worn
  • Must be reset after properly inflating every tyre
  • Must be reset after routine tyre rotation.

Direct TPMS

Direct TPMS uses pressure monitoring sensors within each tyre that monitor specific pressure levels, not just wheel revolution data from the anti-lock brake system.

Sensors in a direct TPMS may even provide tyre temperature readings. The direct tyre pressure monitoring system sends all of this data to a centralised control module where it’s analysed, interpreted, and, if tyre pressure is lower than it should be, transmitted directly to your dashboard where the indicator light illuminates. Each sensor has a unique serial number. This is how the system not only distinguishes between itself and systems on other vehicles, but also among pressure readings for each individual tyre.

Replacing a TPMS in a way that’s consistent and compatible with your vehicle will require an experienced, knowledgeable technician.

Advantages of Direct TPMS

  • Deliver actual tyre pressure readings from inside the tyre
  • Not prone to inaccuracies because of tyre rotations or tyre replacements
  • Simple resynchronisation after tyre rotation or tyre replacements
  • Batteries inside the sensors usually last for between 5-7 years.

Disadvantages of Direct TPMS

  • More expensive overall than an indirect TPMS
  • Though simple, resynchronisation may require costly tools
  • Battery rarely serviceable; if the battery is drained, the whole sensor must be changed
  • Proprietary systems make installation, service, and replacement confusing for drivers
  • Sensors are susceptible to damage during mounting/demounting.

Although the methods may be different, both systems serve the same purpose and activate the same indicator light. Eventhough a TPMS can deliver accurate alerts when properly maintained, it’s not a replacement for manual air pressure checks.