Discussing Brake Wear Indicators and Brake Wear Sensors
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- Опубликовано: 22 авг 2018
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In this week's training video, we walk through the evolution of brake wear indicators and brake wear sensors.
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Pad Wear Indicator:
The original pad wear indicator was actually integrated into the brake pad itself. In fact, many manufacturers still use this pad wear indicator today.
The indicator is actually a piece of metal connected to the pad’s backing plate or shim. The piece of metal protrudes about two to three millimeters past the backing plate.
When the pads wear down past two to three millimeters, the metal will make contact with the rotor. This produces a high-pitched squealing noise. That squeal tells the driver that it is time to take their vehicle in for a brake job.
Electronic Pad Wear Sensors:
The original electronic pad wear sensors are a loop of wire with a small electric current in it. The sensor has a known resistance, usually 2,000 ohms. The wire connects near the brake pad very close to the rotor.
Once the brake pad wears down past a certain point, the rotor will start rubbing up against the wire. Eventually, the wire will break and the change in resistance will cause the brake wear indicator to light up on the dashboard.
Two-Stage Electronic Pad Wear Sensors:
Many German manufacturers, including BMW, have recently released a two-stage pad wear sensor. These sensors are able to do more than warn the driver of a worn brake pad. They can actually estimate how many miles a brake pad has left.
These sensors are called two-stage sensors because they have two sensors integrated into the wire. There are two resister circuits at two separate depths in the wire.
When the first resister circuit breaks, usually halfway through the pads lifecycle, At this point, the vehicle’s information center will begin measuring things like:
• mileage
• wheel speed
• brake pressure
• brake temperature
• brake operating time
The computer will use this information to calculate the life left in a brake pad.
This first stage will not trigger the light on the dashboard. Some systems may show the life left on the brake pads when you start the vehicle. Others will list this in the information center on the
dashboard.
Once the second wire breaks, a brake wear indicator light will light up on the dashboard.
Using the Parking Brake Module to Track Rear Pad Wear:
Some manufacturers, like Mercedes Benz, use the electronic parking brake module to track rear pad wear. The system counts the number of times the stepper motor rotates to apply the back brakes.
By doing this, the system can calculate how much life is left in the rear pads.
Replacing an Electronic Wear Sensor:
When sensors fail or contact the rotor, some technicians cut the two wires and twist them together rather than replace sensors. This turns the brake wear indicator light off on the dash, however, this is not a professional repair procedure.
This method will not work with the new two-stage electronic wear sensors. The sensors will notice that there is no voltage dropping across the circuit and will trigger the light on the dashboard.
As a general rule of thumb, it’s always a good idea to replace wear sensors during a brake job. Make sure to route the wiring through the factory brackets during installation.
Finally, make sure to reset the brake life service indicator on the dashboard. On some vehicles, you can reset this light on the dashboard. On other vehicles, you will need to use a scan tool to
reset the indicator. 
Авто/Мото
Finally, a good video explanation about this mysterious indicator
thank you. saved me from a heart attack
Very good video thank you.
Thank you for this
Never needed such things once I got married.
My wife typically reminds me to replace the brake pads every 20 to 30 trips to the market.
Sure, that's a LOT of wasted brake pads, but a Happy Wife is a Happy Life. 😃
That was really helpful, thank you! I am having front/back brake pads, front/back brake discs, and all four tyres replaced and was curious when the brake sensors on each axle were to be replaced. It looks like we can use the old brake sensors as long as they haven't shorted or tripped.
So which side does it go on
12 jan 2020 3:22 pm est: thanks.0:31 brake-pad-wear-indicator scrape brake-disc automatically without needing to press foot-brake. so there is automatic-brake-pad-gap-adjuster which make sure gap between brake-pad and brake-disc always same, even though brake-pad-thickness decrease after brake-pad-degradation from braking.
Strangely, I hear a slight screech and skipping noise when I press the brakes and it goes away when I take my foot off the brake pedal and accelerate. Just the opposite of what the mechanic said. Anyone any ideas as to what may be going on? Thinking about buying new front rotors and brake pads. My rotors are only 3 and a 1/2 years old. Thanks.
Question what is the proper location for the pad with the low sensor metal clip thanks
Inboard, and usually the wear sensor tab should be on leading edge with the rotor meeting the sensor first when driving forward. Whenever replacing pads, make note of how the current pads were installed and do it the same way. This of course assumes the previous pads were installed correctly. When in doubt, ask a professional tech and buy them a beer ;-)
I had my vehicle parked outside on my driveway for about a week or so. It's still new with only 200 miles on it. Then yesterday I decided to take it for a drive. However, when I released the parking brake and began rolling off my driveway, right before it moved forward, there was a loud thump or clank sound.
I was slightly worried at first as I have never experienced this sound before. Is this normal? Does anyone have any idea what this could have been? 🤔
probably rust, which developed while your vehicle was parked for a week. The sound occured because the bond between rotor and pad surface broke free from vehicle movement.
This guy looks like James Hetfield! 🥂 Ty good info here!
How come I only hear it when making sharp turns?
How often do people replace brake pads .. I'm a guy with 0 experience in Car and im about to own my first car and im curious.
Depends on how you drive. If you're driving fast and thus stopping harder, then more often. If you're driving more smoothly then you should be good for a while honestly. You can visually check the breaks just by looking at them from the outside too, provided your rims aren't blocking a ton of your view. If they're still pretty thick, you've got some life left in em. If they're starting to look thin, consider a new set.
Replace them as soon as they start making that “screaming” sound
Pff! Bludy electronics, gimme old school squealers anyday