Tyre Pressure Monitors

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Dave Richardson

MB Enthusiast
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Joined
Oct 14, 2007
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1,049
Location
Plymstock Plymouth
Car
W176 A class 180 cdi
My W176 according to the Vin sheet has tyre pressure warning loss fitted (477), yet all four wheels have standard rubber valves fitted ; I hadn't noticed this until I bought a s/h wheel to replace one that had been damaged by hitting a pothole & the s/h rim had a genuine pressure sensor fitted.

When checking TP on the dashboard I've been receiving a message stating 'tyre pressure ok' is this normal/ how could my tyre pressure be assessed if standard rubber valves were in use?

Anyone please ?
 
There are two types of TPMS.

Yours is the basic one that works-out tyre pressure loss by comparing the rotation of the wheels with each other. It uses the ABS sensors and ESP software.

It used to be sold as an 'option' (I think they used to charge £50 for it), but it later became mandatory in the EU and now it's standard on all new cars.

The other system does have RF tyre pressure sensors incorporated into the tyre valves.

The difference is that the basic system can only detect a significant loss of pressure in one wheel compared to the other wheels, and only if calibrated (reset) correctly in the first place, i.e. after each time when you top-up the air in the tyres, but it won't know if the air pressures are correct or not. So all 4 tyres may be under-inflated or over-inflated, the TPMS won't warn you.

The more sophisticated system will obviously know the individual air pressure in each tyre (and on most models also the temperature), and will warn you if the pressure is incorrect in one or more tyres.
 
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