typre pressure light thingy

[briSk]

does the tyre pressure light come on only when you have a puncture OR just if (somehow) the pressure have got too low?

it was flipping freezing this morning and i haven't checked the pressures for about two weeks so i guess the pressure in one could have got pretty low..???

anyway the point is - the first course of action is to pump the tyres up and reset and see if the light comes on again tomorrow AM - right?

ps what pressure will you get if the tyres has a puncture - i mean the difference of a runflat is all the metal holding it up - right? - so if it has got a puncture the pressure should still have got really low..right?

[esuuv]

I believe the system works by checking the rotational speeds of the wheels - a flat tyre has a smaller overall diameter and therefore will turn faster than the other three. Therefore if you have low pressure in one then yes the car will warn you.

I'd check the pressures in all of them - press the reset button - on the left of the drivers seat somewhere on an R53, no idea on a R56 (I really should find out) and see what it says.

And yes the runflat is just a very stiff sidewall holding the tyre up - so one with a puncture will have a very low pressure.

[briSk]

thank you for your confirmation.

i sent the wife out and the right front was down to 1.5 bar (!). so she's put more in and reset it. if after an afternoon's parking in her car park has it go down that much again then i guess we can be sure it's rogered (rather than it being a big impact or something..).

it needs new rears soon anyway so it looks like we're looking at a set now..!