Flat tyre sensor

D

DR-Z

Member
 Ashbourne (Derbyshire) and Aberdovey
I put new front disks on a few weeks back. For the past couple of weeks I've been hearing a sort of rythmic rubbing noise from the LH side of the car, when I drive close to a wall or hedge and the sound bounces back. Seems to be in timing wihth wheel rotation, so I assumed it was something to do with the new disks.

Yesterday I took the LH disk off to make sure there was no dirt preventing it from seating properly. Noise still there. This morning I decided to check tyre pressures, and discovered there's no pressure at all in the rear tyre! Run flat, completely flat. Nothing visible to the eye of course.

So, I've been driving with a flat for the past two or three weeks, several hundred miles, and not taking it easy round the bends! A good testament to RF tyres, I suppose, but I would have thought the flat tyre indicator would have alerted me? Faulty sensor?

So an opportunity to to move to real tyres on the back, or maybe all-round, depending on how much I have left on the fronts.
 
Change all at the same time, not really a good thing mixing run flats and non though many have done it.

Were the other three up to pressure?
 
I think that to trigger the sensor the change in wheel rotation needs to be quite sudden to trigger the sensor. If you have not checked the pressures for a few weeks ( :poke: ) and even then not reset the sensor when you have put air in, it throws the system out of whack.
 
I checked the tyre pressure sometime last year! Maybe time I did it again.
 
And if they drop slowly, it won't tell you. I know it is called a tyre pressure monitoring system, but it's not really, it's a puncture warning system. Go figure :idunno:
 
So what does the sensor actually do? A quick search of the internet suggests there are two approaches to this, one monitoring low pressure, the other linked to the ABS:

http://www.etyres.co.uk/run-flat-tyres

Which system does the Z4 use?
 
I believe it's the ABS system, which monitors wheel rotation speed. There are certainly no sensors in the wheels themselves.
 
Yes, the system works from the ABS and monitors the difference is rotational speed between wheels on the same 'axle'.

With a loss in pressure the rolling radius of the tyre changes and the system reports it as a loss in pressure. It does state " ... is unable to warn the driver of sudden, severe tyre damage caused by external factors, nor can it identify the gradual loss of pressure...." so not infallible or that reliable and certainly doesn't replace the need to check tyre pressures.

It's all in the manual.
 
I parked at my mate's and came out a few hours later to a flat front tyre and the tyre sensor didn't light up when I drove away..don't really trust them
 
Worked perfectly on mine the other day. I had done the pressures last week, red light came on Monday morning, drove very carefully home and found my rear tyre slightly deflated with a fecking huge screw in it. I was very glad of the system tbh because without it I may not have noticed, then ended up with the screw coming out at speed on the motorway...
 
You must log in or register to reply here.
Back
Top Bottom