Tyre Pressure Monitors

[Sheroo]

Does anyone know how these work, they are abit of a disappointment as I thought they would indicate what the actual reading was for each tyre.

I am thinking of changing the 18" alloys to 19" but am not sure what to do about the TPMS ?

[two_paracetamol]

As I understand it (and no doubt someone will correct me if I'm wrong) they use the ABS sensors to monitor the rotation of each wheel. If a tyre starts to go flat the circumference of that wheel gets slightly smaller so it rotates faster than the other tyres and sets off the alarm...

Therefore I would guess that as long as all the tyres are the same size (be it 18s or 19s) then the TPMS wouldn't be any the wiser.

Anyone know any different?

[JBlues]

As I understand it (and no doubt someone will correct me if I'm wrong) they use the ABS sensors to monitor the rotation of each wheel. If a tyre starts to go flat the circumference of that wheel gets slightly smaller so it rotates faster than the other tyres and sets off the alarm...

Therefore I would guess that as long as all the tyres are the same size (be it 18s or 19s) then the TPMS wouldn't be any the wiser.

Anyone know any different?

I think you're spot on. Both Ford and Renault offer systems that show the individual readings from each tyre which is to me what most people would want. However, it is a useful feature if nothing else to give you an early warning of a punture which if you do a lot of motorway driving could save you and any other occupants. VW did the same with the B6 Passat - slighlty different system in that it works by having special valves in the tyre to detect any drop in presure, that too held short of showing individual tyre values and alsp if fails to show which tyre has the problem just that you have one somewhere!

[mkc]

The system fitted to Audi as you can see does not offer the exact pressure in the tyre. The system works off the ABS sensors that measure the speed of the rolling diameter of the wheel, if one wheel deflates the speed of rotation will change.
This system is a lot more reliable than more complex systems that use pressure monitoring valves. So this type of system is only good for telling you that you may have a puncture, but you should not rely on it as a means of not ever checking your tyre pressures as normal. If the tyre pressure goes down it takes a shorter time to rotate. so only good for a slow puncture anything more serious you will notice anyway.


So I would suggest that changing the wheel and tyre will not effect this system, assuming you go up an alloy size on each corner so diameter is the same!!!. Thats how I think it works anyway.

[browellm]

You would just re-calibrate the system after a tyre/wheel change.

It's a bit of a pointless system anyway, unless your tyre strategy is runflats.

[B6Andy101]

If you're running 19" rims its usefull. You will not spot a slow puncture visually until the rim is almost on the deck (probably feel it before your see it) Dont need to know the pressure, just if your losing it :D