Tyre pressure monitors become law

Posted on November 25th, 2014 by Rob Marshall

Ê%ËËAs a nation, we are not very good at looking after our rubber ware. Halfords’ Autocentres has reported that 8.5% of cars that the company either serviced, or MoT’d, possessed at least one tyre that was in a dangerous condition. Tyresonthedrive.com has also highlighted that 90% of British motorists do not check them at least once-a-month, even though weekly inspections are preferable. Therefore, it can be argued that higher fines and more endorsements on your driving license (currently three penalty points for each defective tyre) are not working.

To try and reduce the number of road traffic incidents, caused by under-inflated covers, all new cars had to possess tyre pressure monitoring systems (TMPS) as standard equipment, from 1st November, 2014. These systems not only warn the driver of a puncture but they also flag-up a low pressure warning, should it fall below a certain level in each tyre. Apart from the safety benefits, a tyre that has been inflated correctly will last longer and will also realise better fuel economy. Of course, the danger is that drivers might over-rely on the technology and presume that tyre checks are necessary only, when they are warned by the system.

Most TPMS are of the ‘Direct’ type, where a sensor is placed within the wheel rim (see picture). They tend to be fully sealed and send a wireless signal to a receiver, located within the car bodyshell, at least once a minute. The sensors’ internal battery lasts between 5 and 8 years and renewal can be surprisingly expensive. Not only does the sensor have to be replaced but a new unit has to be activated and coded to the vehicle, necessitating the use of expensive diagnostic equipment. A typical per sensor price, for all of this work can vary between £60 and £100. However, as sensors become more commonplace, the price is certain to fall, as more competition enters the market and economies of scale are realised.

While TMPS has been fitted to an increasing number of cars, since the early 2000’s, there are a number of things that you can do, to lengthen their life. Unlike conventional tyre valves, you do not have to renew the entire sensor at every tyre change. The internal valve core and outer seals can be replaced on most types and service kits tend to be available for between £2 and £10. Secondly, inspect the sensor’s valve stem for corrosion. We have heard of some metal stems disintegrating, when the cap is removed, causing an instant tyre deflation. Although many fitters should be able to tell if a sensor is present by sight alone, advise the operator anyway, to reduce the risk of the part being either knocked, or damaged, by the tyre removal machine.

TPMS will also be included within the MOT Test’s scope, from next year, but the available advice is not entirely clear, especially for older cars that have been retro-fitted with the technology. We will be able to provide a definitive answer soon in a future blog.