[e90328isf]

I am the first owner of a 2011 Bmw 328i with 65K mi almost all highway miles - I just replaced the original tires which were not worn but simply too old.

I had the rear brakes indicator come on a couple of times telling me the brake pads are worn - I could see plenty of brake pad left and to be sure I took it to the mechanic who also said there is about 60% left. A week after I reset the sensor light, it came back on.

I know that the worn brake light comes on both based on milage and based on the brake sensor reading and since it came right back on it makes me think that it actually could be the brake sensor reading rather than the milage based calculation triggering the warning.

What is puzzling is that there is a lot of material left on the brake pads and I wanted to see what others are thinking. Could it be a bad sensor, etc? Thanks!

[nhhiep]

100% bad sensor. things like brakes where you can check with eyes, don't trust the sensor. unless it's underwarranty to get free replacements

[e90328isf]

Originally Posted by nhhiep

100% bad sensor. things like brakes where you can check with eyes, don't trust the sensor. unless it's underwarranty to get free replacements

Thanks. Is there a way for me to check if the sensor is bad - or it is not very straight forward?

[tcphoto]

Inspect the pads, confirm the thickness, buy a new sensor and swap it out. If the pads are worn the indicator would give you about 600 miles till you need to do brakes.

[jwalker87]

Of note, since I've seen some terrible mechanics in my days, is that the sensor monitors one of the inside pads, so you would really have to get in there to see the pad thickness. My dad had a mini that started eating through the rotors because his mechanic didn't notice the inside pad was GONE while the outside looked fine.

Could still be a faulty sensor, but I tend to trust indications until proven otherwise. Just make sure you prove to yourself otherwise.

[e90328isf]

Originally Posted by tcphoto

Inspect the pads, confirm the thickness, buy a new sensor and swap it out. If the pads are worn the indicator would give you about 600 miles till you need to do brakes.

thanks, good point

[e90328isf]

Originally Posted by jwalker87

Of note, since I've seen some terrible mechanics in my days, is that the sensor monitors one of the inside pads, so you would really have to get in there to see the pad thickness. My dad had a mini that started eating through the rotors because his mechanic didn't notice the inside pad was GONE while the outside looked fine.

Could still be a faulty sensor, but I tend to trust indications until proven otherwise. Just make sure you prove to yourself otherwise.

thanks, I am not sure if he checked the inside and I did not too - I did have a car which wore the inside and outside unevenly so that is a good point

[Vivek.]

Originally Posted by e90328isf

thanks, I am not sure if he checked the inside and I did not too - I did have a car which wore the inside and outside unevenly so that is a good point

Just about every car will wear the inner pad more than the outer. Always best to assume that the inner which you cannot easily see is (10-40%) thinner than the outer.

[e90328isf]

Was also wondering why the rear also wore faster than the front? I guess if the rear ones are actually worn I should replace fronts as well

[Efthreeoh]

On BMW 3-series, the brake pad wear sensor is always on the pad that is on the piston-side of the brake caliper. The single-piston calipers always place the piston on the inside location so the wheel spokes can fit close to the hub and clear the caliper. If you have a sticking caliper, the inside pad could be worn while the outside pad is not.

It could be a situation were road debris caught the pad sensor harness wires and broke the sensor connection, which would trigger the light. Or possibly a rodent chewed on the sensor harness. What you need to determine is if the first stage of the pad sensor has been triggered. If the sensor has not been rubbed down past the first sensor wire imbedded in the sensor body, then you can just replace the sensor and not worry about it. If the first stage wire is broken, and the sensor wire harness is damaged, to replace the sensor, you should set the new sensor to be past the first stage as well, so as to not confuse the CBS computer that is monitoring the pad wear.

65,000 highway miles may not yet have tripped the first stage of the sensor. You'll have to inspect the sensor face closely. There are a specs somewhere for the resistance of the readings for sensors with the first stage being tripped, but I can't find it at the moment.

[mook1178]

After having my tires replaced one time, my front sensor triggered about 30 minutes after leaving the tire shop.

The person replacing that tire knocked the white clip from the sensor to the brake line and did not clip it back. going around the turns, the sensor was snapped, throwing the light.

[e90328isf]

Originally Posted by Efthreeoh

On BMW 3-series, the brake pad wear sensor is always on the pad that is on the piston-side of the brake caliper. The single-piston calipers always place the piston on the inside location so the wheel spokes can fit close to the hub and clear the caliper. If you have a sticking caliper, the inside pad could be worn while the outside pad is not.

It could be a situation were road debris caught the pad sensor harness wires and broke the sensor connection, which would trigger the light. Or possibly a rodent chewed on the sensor harness. What you need to determine is if the first stage of the pad sensor has been triggered. If the sensor has not been rubbed down past the first sensor wire imbedded in the sensor body, then you can just replace the sensor and not worry about it. If the first stage wire is broken, and the sensor wire harness is damaged, to replace the sensor, you should set the new sensor to be past the first stage as well, so as to not confuse the CBS computer that is monitoring the pad wear.

65,000 highway miles may not yet have tripped the first stage of the sensor. You'll have to inspect the sensor face closely. There are a specs somewhere for the resistance of the readings for sensors with the first stage being tripped, but I can't find it at the moment.

All good points, thanks! I did go check the inside brake pad and sensor and the brake pad is not worn and the sensor is not touching. Will do a soft reset again through the dash and if it goes off again will replace the sensor. The dealer quoted me at $50 for the sensor, but I see them everywhere for like $15 - not sure if they are oem, probably not

[e90328isf]

Originally Posted by mook1178

After having my tires replaced one time, my front sensor triggered about 30 minutes after leaving the tire shop.

The person replacing that tire knocked the white clip from the sensor to the brake line and did not clip it back. going around the turns, the sensor was snapped, throwing the light.

everything looks like it is still connected properly, if after I reset the warning comes back, I will just replace the sensor. thanks for the information