Brake Pad Warning Lights

A

Andy

Veteran
 Warwickshire
I had my front pad replaced about 4k miles ago and it needed discs too surprisingly, after the warning light came on and it needed a service anyway.

they warned me at the time about my rear pads, saying they were getting fairly close but as it was only a advisory i thought id wait until the light came on again as i hadn't budgeted for the discs at the time.

so anyway, fair few miles of hard driving later and there's no warning light, but there's an occasional griding from the back brakes when it's cold. :thumbsdown:

should the rear pads trigger the light too? I'm going to try and find it in either the z4 or z4m supplement manual and try and complain - I'm assuming it needs pads and now probably discs too. Anyone else had rear pads after the warning light?
 
On all my BMW's I have had to replace pads and discs at the same time, the last car a 320cd M Sport all were replaced within 20k which I thought was bad, only saving grace was BMW paid for it as it had a free service and maintenance package when new.
 
If the ///M is the same as the non ///M then you shoudl have a brake wear sensor on the front NS and Rear OS. Either should trigger the warning, but I would not rely on that and have a quick visual check of the remaning pad thickness.
 
Yes the light comes on for front and back. My rears disks had quite a lip so I had them changed, thats at 40K miles.... As for the grinding, I have noticed that the refreshed OEM set up sounds different to when the car was new, thats with new pads / disks on each corner. I wander if the pad compound has changed slightly or the material in the disks is different.

Other reasons :

a) There is a disk drying feature is there not, is this kicking in when coming to a stop or early on in a journey.
b) the build up from the car standing (surface contaminents etc) being cleared away from the friction?
c) caliper binding ? - Unlikely I guess but still....
 
Andy,

how many miles had you done when pads failed?

I was told I needed discs by a National Exhaust and tyre outlet on my work car (a Citroen) when it needed front pads, I made him show me using the micrometer device he had and he didn't know how to use it. We agreed to leave the discs alone after that!! :)
 
Andy,

The wear sensor is only fitted to one side, if you have had uneven wear or possibly a sticking caliper it is entirely possible the pads on the side without the sensor are worn out, but the sensor side still be ok. Worst case scenario is they shorted out the sensor just to make the light go out, not common practice by dealers, but has been known by lesser independents. The wear sensor is just a cable loop once it goes open circuit it lights the bulb on dash so it relies on the cable actually failing. Typically brake balance is front biased so more wear on front than rears is not unusual.

An occasional grinding could be caused by the reasons listed by ali_b, i would concur with jeeper, check what lip you have on disc and amount of pad left bearing in mind the inside pad could potentially have more wear than the outside if caliper hasnt released properly.

And a comment on sammyz post....... kwik fit once told me my front shocks were leaking fluid and i needed replacements....... should have seen the guys face when i asked 'just exactly do gas filled shocks leak fluid??' :rofl:
 
Just for reference. Z4M Coupe has pad sensors at each wheel. If the light comes on. There's nothing left so change the pads straight away.

Chris
 
ChrisCSL said:
Just for reference. Z4M Coupe has pad sensors at each wheel. If the light comes on. There's nothing left so change the pads straight away.

Chris
Click to expand...

Thats not stictly true. There was a good 0.75 of a CM left on mine having changed them today.

1000-2000 miles depending on how driven.
 
SeanConnor said:
Get it checked. I had an expensive lesson with my other jalopy an Octavia VRS. Slight grinding noise on N/S rear. I took it in after about a week and it was a partially seized caliper. Result .. a set of rear rotors and pads plus a new caliper.
Click to expand...
Wow, a 6 year old thread resurrection :poke:
:P
 
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