Brake wear sensor

[andyw]

I have just changed my front discs and pads. After 62,000 miles the discs were approximately 70% worn but the pads were almost down to the backing plates. There was 2-3mm of material left on the ones that sit on the pistons, a bit more on the static ones.

It raises the question do the wear indicators work. How do they work? I am wondering if there is any point replacing them.

If I do decide to fit a new one where is the break point on the wiring loom. Is it in the wheel arch or under the bonnet?

Thanks in anticipation

Andy

[Simon]

The brake pad wear indicators are not to be relied upon as a measure of your pads wearing. They cannot (of course) detect how much your discs have worn, they are only for the pads.

As with all safety devices, think of the pad wear indicator just as that "an indicator" and maintain regular checks.

That said, they ought to work reasonably reliably so for one to not show a worn pad could indicate a faulty or incorrectly installed sensor.

If you do wish to bypass the sensor then you should find the connecting block if you trace the cable up from the pads as it travels up into the wheel arch.

Another note: There is only one indicator per axle. (ie one on the front and one on the back). Therefore it is entirely possible that one set of pads could have worn before the set with the indicator on them had worn to a sufficient level to trigger an alert on your dashboard.

The indicators work by completing a circuit. As the pad wears away, so do the wires in the sensor. When all the wire has worn away, there is no longer a circuit and so the car detects and alerts you to this event

[andyw]

That's interesting information Simon. The 30,000 service was done by the dealer. Since then I've done three oil services and now we arrive at the current 60,000 service.

I knew the discs were getting ready because I had a pair of new tyres recently and the fitter told me in a hopeful tone of voice that the discs had a lip on them and were almost ready to be swapped out.

I had a look at them and the micrometer showed a thickness of 20mm. Minimum thickness is 19mm. New ones start out at 22.5mm.

I have shopped around and bought a set of Mintex discs and pads. Fitting them was straight forward but did involve breaking the sensor. I noticed that the sensor was shiny on its tip. I have tied it up out of the way until I source a new one but this has not caused the brake warning light to come on. From what you have said it sounds like the light should have come on.

I traced the wire back up the wheel arch until it disappeared through a rubber grommet but I couldn't spot a connector block which is what led me to believe it wa possibly in the engine bay

Andy

[Simon]

If you break the connection for the sensor then the "Low Pad" warning light will come on your dash.

By tying up the sensor you have effectively removed it from wearing away - hence it will remain "intact" and will not show up on you dash.

It is recommended to always replace the wear sensor with a new one when you change the pads. There ought to be a connector somewhere :shrug: I think it's usually located somewhere before the wiring enters the wheel arch.

As I say, only one sensor per axle and the sensor will only detect pad wear not your discs. Replacing discs alone will have no impact on your pads and as a consequence have no affect on your wear sensors.

Worth noting there is also a sensor for the ABS located on one wheel per axle too. The sensors are entirely different from each other - but a word of caution so you just don't go snipping wires willy-nilly... :D

[JohnDotCom]

It is recommended to always change the Pad wear sensor when changing pads.
It is generally broke/worn out then anyway.
The Club cannot recommend/condone that you you bypass the sensors as they are designed as part of the cars Warning system.
They are available Cheaper on EBay or throuch EPC Car Parts, Sandy, Beds.

[Simon]

:iagree:
Yes, of course. Should have stated that the sensors are there for a reason so best not bypass them. Personally I would like the reassurance of the sensors being present and functioning - I would personally feel a little insecure knowing that they weren't there. :) :cool:

[crofts]

That's interesting information Simon. The 30,000 service was done by the dealer. Since then I've done three oil services and now we arrive at the current 60,000 service.

I knew the discs were getting ready because I had a pair of new tyres recently and the fitter told me in a hopeful tone of voice that the discs had a lip on them and were almost ready to be swapped out.

I had a look at them and the micrometer showed a thickness of 20mm. Minimum thickness is 19mm. New ones start out at 22.5mm.

I have shopped around and bought a set of Mintex discs and pads. Fitting them was straight forward but did involve breaking the sensor. I noticed that the sensor was shiny on its tip. I have tied it up out of the way until I source a new one but this has not caused the brake warning light to come on. From what you have said it sounds like the light should have come on.

I traced the wire back up the wheel arch until it disappeared through a rubber grommet but I couldn't spot a connector block which is what led me to believe it wa possibly in the engine bay

Andy

Hi Andy. You will see the connector when you obtain a new sensor. Follow the wire up from the wing, under bonnet. I found it quite fiddly to get at the connector to disconnect and plug in new one as space is limited. Don't know why they had to 'hide' it !