Can someone confirm how the RCF wear sensor functions. I've attached a picture of the front left brake caliper. It would appear that the metal sensor tab is about to make contact with the rotor. I'm currenlty at approx 21 K miles.
I would imagine as soon as that happens a brake warning light will go off in the dash. The dealership informs me though that as soon as the sensor makes contact with the rotor, the sensor will be damaged and it will have to be replaced???
Using some measurement calipers I am currently at approx 4 mm of pad left. I thought I saw a spec posted by lobux that the absolute min allowable pad thickness is 1 mm? I'm thinking I'd like to push to about 2 to 3 mm.

wolfman

 

I know other manufacturers will include the sensors with the brake pads. I would ask Lexus parts store to see if it comes with it.

 

There's a piece of wire that will break apart from wear after contacting the rotor, for how long, I don't know. So yeah, when the warning light goes off, a sensor replacement is needed, along with new pads of course. If you replace the pads now before the sensor trips the warning light, you save yourself from buying a new sensor. EDIT: if they're not included with new pads.

 

Your OEM brake pad replacement comes with sensors built in. Whether you wear out the pad all the way until the sensor trips or not you will still get replacement brake pad with new sensors. It doesn't cost you a penny more. My service advisor was actually surprised when he was advised by the parts department that I do not pay an extra/separate charge for new sensors as they are already built into the brake pads. Yes, I did drive mine until the brake wear warning light kicked in. Squeezed all my money's worth out of those brake pads for sure.

 

The wire comes in the brake kit with the OEM pads. If you buy aftermarket pads, you can buy the wire separately.

04465-0W190 Front brake kit (pads, wires, and Brembo copper paste)
47770-24010 Front wear sensor (only the sensor, need to order 2)
90998-94072 Brembo copper paste

Looks like this part is about $75. It does one thing - allows you to get the most wear out of your brake pad without damaging the rotor when you start with a new rotor. Once the rotor wears and develops a lip, then the pad will actually have more than minimum life left when the sensor indicates the pad is done. With sufficiently worn rotors, the pad backing plate will touch the wear induced lip before the pad material is gone (AMHIK) and the squealing will definitely make you want to change pads and likely rotors because they will be near service limits for wear.

There are lots of different perspectives on brake system wear - what to do and when to do it - but the sensors only job is to notify the driver the brakes need attention before the rotors are damaged. Some rotors are pretty expensive so this makes good economic sense. Others are not so expensive, so it makes no economic sense at all. Your brakes will stop your car, even if all the pad material is gone. See my track pads below - I got to this point after 15 sessions of 20 minutes at speed and heard the clank of metal on metal when I was getting ready to get gas for my next session. My rotors were undamaged, and I put my street pads back in to drive home to Atlanta 4 hours away.



If you remove ALL the pad material, they will make horrible noises and the rotors will be irreparably damaged, but the car will stop (I noticed no loss of stopping ability ON THE TRACK with the pads above). Anyone who has worked in a shop long enough can tell you stories of metal on metal brakes. Steel backing plates on cast iron rotors isn't as awful for stopping as many would like you to believe.

So the manufacturers have cut with a double edged sword here. They've raised the cost of a brake job by $300 (all four sensors) to ensure you are aware your pads are getting thin enough to need replacement before they damage the rotors. They've also saved you from unscrupulous service advisors who tell you dumb things like - you only have 3mm of brake pad left, we really should service the brakes with new pads, turn your rotors, etc., etc., to only benefit their profit numbers for the month. With the sensor, you can just say, I don't see any reason to change them until I see the indication on the dash, and it's a reasonable conclusion. I am sure there are SAs out there who will tell you to change your pads even though the sensor hasn't gone off yet with similarly bad logic, but at least you now have a tool to help defend yourself against unnecessary brake pad changes.

 

Thanks all for the great replies.

Was under the car looking at the brake pads and sensor over the weekend. My plan is to go with Project Mu street pads. I've heard great reviews and the dust is a lot better. Thus, I was looking to save the sensors for the new pads. Since I know I have about 4mm of pad material left and I do my own maintenance as much as possible, I was planing to tie the sensors back until the new P Mu pads arrive. Tried to remove the sensor from the old oem pads without removing the pads from the caliper but was not able to? Tried gently even with pliers but could not get them out. I accidentally pulled on the sensor wires as the pliers slipped off the sensor body and it seems to have dislodged the wires a bit. Was able to tuck them back in and no warning lights have come on. Hope the sensor is ok.

wolfman

 

So if we switch out the pads early enough, can we reuse the sensors for the new brake pads? Mainly if not going with OEM pads since they already come with new sensors? I'm also looking to switch to project Mu but would like to save myself the cost of new sensors if at all possible.

 

My sensor is a flashlight. Every month or so, I physically check the pads (front and rear) to see how much meat is left. That way I can anticipate when it's time or close to time to change pads. Rather than having an acoustic warning telling me to do it NOW

Lou

 

Maybe. It might be difficult or impossible to remove the sensors without damaging them. See wolfman's post. If it is mechanically possible to remove them, they also might not install properly. This is a trial and error situation.

 

That's what I figured. Just wondering what others have done when switching to other types of pads.

 

Would like to add that, I believe if I had removed the pads from the caliper, it should be possible to remove the wear sensor.

I should also add that going forward my plan is as follows: I believe the wear sensor is a Normally Closed contact. Wear on the sensor causes the contact to Open, destroying it, and leading to a warning to show up on the dash. I'm thinking of cutting the sensor out (since it's about to be destroyed any day now) and then soldering the two wire leads together. I will probably cut right after the rubber boot on the bleeder screw that holds the sensor harness in place along the top back side of the caliper. This will give me a permanently Normally Closed contact. The only downside is I will never get a warning on the dash and I will routinely have to visually inspect the break pads for wear, which I'm ok with.

What do you guys think?

Wolfman

 

that would work. Hopefully it doesn't check for a resistance. Found a lot of brake pad bypass sensor threads for BMWs and they are just jumping the sensor