Brake pad sensor question

TheMidnightNarwhal · 10-11-2018, 05:00 PM

I have an odd one.

I noticed on my car, my rear brakes had the sensor on the passenger side with the new type of sensor without an L shape. My front brakes has the sensor on the driver side with the older type L shape.

My question is, what is the actual difference and I'm wondering if this may be the cause of my rear sensor install issue.

On parts website it says that the older L shape stops after an X amount of production date, which my car falls into but now my car has both.

I just ordered 1 of each new and old for front and rear and I'll just try them but my question is is it simply form factor or the circuitry is different in the old and new?

Anyone else noticed this?

Fritzer · 10-11-2018, 05:19 PM

I have not noticed this, however I'm sure the parts are interchangeable. From what I understand don't you have to pair up each new sensor with the pad in lieu of inaccurate readings? Or is that just after the sensor has signaled?

I have a weird one where my sensor triggered only from the inner, front left side brake pad. The rest of the pads all have about 10,000 miles left and the rotors look okay.

TheMidnightNarwhal · 10-11-2018, 05:30 PM

Quote:

Originally Posted by Fritzer

I have not noticed this, however I'm sure the parts are interchangeable. From what I understand don't you have to pair up each new sensor with the pad in lieu of inaccurate readings? Or is that just after the sensor has signaled?

I have a weird one where my sensor triggered only from the inner, front left side brake pad. The rest of the pads all have about 10,000 miles left and the rotors look okay.

I had to change brakes recently and my rear brake sensor probably didn't fit properly and fell and snapped the sensor so I got the warning now.

And my fronts are due to change soon to that's why I got them.

If you have wear on one side only probably your guide pins need cleaned and lubed back up

Fritzer · 10-11-2018, 05:39 PM

Quote:

Originally Posted by TheMidnightNarwhal

If you have wear on one side only probably your guide pins need cleaned and lubed back up

Didn't even think of that! Yeah I'm going to probably change the fronts in 3 months or so, just did the rears. Have to put some money aside for insurance deductible on new bumper. Hopefully I can squeeze in a M-Tech finally. Then pay out of pocket for a rear M-Tech later on.

OTO335i · 10-11-2018, 06:31 PM

Quote:

Originally Posted by TheMidnightNarwhal

Quote:

Originally Posted by Fritzer

I have not noticed this, however I'm sure the parts are interchangeable. From what I understand don't you have to pair up each new sensor with the pad in lieu of inaccurate readings? Or is that just after the sensor has signaled?

I have a weird one where my sensor triggered only from the inner, front left side brake pad. The rest of the pads all have about 10,000 miles left and the rotors look okay.

I had to change brakes recently and my rear brake sensor probably didn't fit properly and fell and snapped the sensor so I got the warning now.

And my fronts are due to change soon to that's why I got them.

If you have wear on one side only probably your guide pins need cleaned and lubed back up

I took the sensor off my rear pad, wrapped the bundle of wire up and tucked it in the wheel well so that i never get the warning light. I'll eventually do the same with the front.

This way ill never have the annoying light and I'll never need to buy sensors.

TheMidnightNarwhal · 10-11-2018, 10:15 PM

I compared both sensor one the raised hump is a bit higher.

Efthreeoh · 10-12-2018, 06:16 AM

Quote:

Originally Posted by TheMidnightNarwhal

I had to change brakes recently and my rear brake sensor probably didn't fit properly and fell and snapped the sensor so I got the warning now.

And my fronts are due to change soon to that's why I got them.

If you have wear on one side only probably your guide pins need cleaned and lubed back up

The guide pins do not require lube. They can get some black carbon deposits on them that can be removed with steel wool. What most home mechanics do is over torque the living shit out of the guide pins and deform them, which can cause the caliper to bind. The guide pin torque is only 22 pound/feet.

His left front caliper may have a sticking piston.

TheMidnightNarwhal · 10-12-2018, 06:59 AM

Quote:

Originally Posted by Efthreeoh

The guide pins do not require lube. They can get some black carbon deposits on them that can be removed with steel wool. What most home mechanics do is over torque the living shit out of the guide pins and deform them, which can cause the caliper to bind. The guide pin torque is only 22 pound/feet.

His left front caliper may have a sticking piston.

Oh wow really? I lubed up my guide pins when I did the rears. Really don't see how negatives it can do. It had lube before to.

fravel · 10-12-2018, 09:19 AM

Quote:

Originally Posted by TheMidnightNarwhal

Oh wow really? I lubed up my guide pins when I did the rears. Really don't see how negatives it can do. It had lube before to.

Yeah, no lube on the guide pins. Overtime that lube will gum up and cause the pins to stick.

TheMidnightNarwhal · 10-12-2018, 09:23 AM

Quote:

Originally Posted by fravel

Yeah, no lube on the guide pins. Overtime that lube will gum up and cause the pins to stick.

Why would lube cause it to stick on a BMW compared to not stick on other cars? Plus this car is the first I've seen where the guide pin is really nicely enclosed and protected.

But ok I guess I'll take out the rear pins and clean them off dry.

fravel · 10-12-2018, 11:00 AM

Quote:

Originally Posted by TheMidnightNarwhal

Why would lube cause it to stick on a BMW compared to not stick on other cars? Plus this car is the first I've seen where the guide pin is really nicely enclosed and protected.

But ok I guess I'll take out the rear pins and clean them off dry.

I'm not sure what the exact mechanism is that causes the lube to not do its job, I just know that on the cars I've done that have had lube put on, when I pull the pins for the next pad change they are all gunked up with a sticky residue. I suspect this residue is the remnants of whatever grease was applied previously. I also suspect that the residue inhibits the ability of the guide pins to slide properly.

Further, the Bentley manual explicitly specifies that you're not supposed to put grease on the caliper pins. I know it seems counterintuitive. Perhaps the reason why the grease isn't needed is because they are so well protected.

Pladi · 10-12-2018, 11:09 AM

Quote:

Originally Posted by TheMidnightNarwhal

Why would lube cause it to stick on a BMW compared to not stick on other cars? Plus this car is the first I've seen where the guide pin is really nicely enclosed and protected.

But ok I guess I'll take out the rear pins and clean them off dry.

For the love of god man dont argue with people that have more experience on DIY than you and are trying to help. They WILL gum up, it happened to me i used to lube them.. break dust and heat degrades the lube.. Some car MFG you use lube because of a different design of the pin. They are sealed more..

I also used top of the line synthetic high temp lube from permatex.. no buenoo

TheMidnightNarwhal · 10-12-2018, 11:34 AM

Quote:

Originally Posted by fravel

I'm not sure what the exact mechanism is that causes the lube to not do its job, I just know that on the cars I've done that have had lube put on, when I pull the pins for the next pad change they are all gunked up with a sticky residue. I suspect this residue is the remnants of whatever grease was applied previously. I also suspect that the residue inhibits the ability of the guide pins to slide properly.

Further, the Bentley manual explicitly specifies that you're not supposed to put grease on the caliper pins. I know it seems counterintuitive. Perhaps the reason why the grease isn't needed is because they are so well protected.

Ok thanks I'll clean it up.

Quote:

Originally Posted by Pladi

For the love of god man dont argue with people that have more experience on DIY than you and are trying to help. They WILL gum up, it happened to me i used to lube them.. break dust and heat degrades the lube.. Some car MFG you use lube because of a different design of the pin. They are sealed more..

I also used top of the line synthetic high temp lube from permatex.. no buenoo

I wasn't arguing I was asking why.

Efthreeoh · 10-12-2018, 11:56 AM

Good Lord, I didn't mean to start an argument. The BMW TIS says not to lube the pins on the E9X chassis. The pins sit in a plastic guide sleeve, which requires no lube. I'm guessing the plastic is some type of ABS due the the high temps the brakes can generate. The plastic is self-lubing is the best way to describe it. Brake dust will gum up the lube if used.

Like I said earlier, the only problem guide pins can have is if they are over-torqued and deform and become out of parallel with each other. Again, the torque is just 22 lb.-ft. People over torque them thinking they are part of the brake assembly and must need to be very tight. All they do is locate the caliper in the carrier, there is actually very little force acting on the thread faces, which is why only a small amount of torque is required.

nsjames · 10-12-2018, 12:11 PM

even the carrier bolts don't need gorrilla torque.

everything in the braking system is a bolt in shear. It just needs to be tight enough to not come out.

Efthreeoh · 10-12-2018, 10:35 PM

Quote:

Originally Posted by nsjames

even the carrier bolts don't need gorrilla torque.

everything in the braking system is a bolt in shear. It just needs to be tight enough to not come out.

Exactly. IIRC the carrier bolts to the hub at around 65 lb-ft.

10-11-2018, 05:00 PM	#1
TheMidnightNarwhal Major General 2800 Rep 6,382 Posts Drives: 11' 335is DCT Join Date: Jun 2015 Location: Gatineau, Quebec iTrader: (0)	Brake pad sensor question I have an odd one. I noticed on my car, my rear brakes had the sensor on the passenger side with the new type of sensor without an L shape. My front brakes has the sensor on the driver side with the older type L shape. My question is, what is the actual difference and I'm wondering if this may be the cause of my rear sensor install issue. On parts website it says that the older L shape stops after an X amount of production date, which my car falls into but now my car has both. I just ordered 1 of each new and old for front and rear and I'll just try them but my question is is it simply form factor or the circuitry is different in the old and new? Anyone else noticed this?
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10-11-2018, 05:19 PM	#2
Fritzer No one sleep in Tokyo 958 Rep 1,506 Posts Drives: 2011 E90 328i//1995 E34 530i Join Date: Oct 2018 Location: San Diego, California -> Austin, Texas iTrader: (3)	I have not noticed this, however I'm sure the parts are interchangeable. From what I understand don't you have to pair up each new sensor with the pad in lieu of inaccurate readings? Or is that just after the sensor has signaled? I have a weird one where my sensor triggered only from the inner, front left side brake pad. The rest of the pads all have about 10,000 miles left and the rotors look okay. __________________ 2011 E90 328i, 1995 E34 530i, 1992 E32 740i, 1991 E34 525i
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10-11-2018, 10:15 PM	#6
TheMidnightNarwhal Major General 2800 Rep 6,382 Posts Drives: 11' 335is DCT Join Date: Jun 2015 Location: Gatineau, Quebec iTrader: (0)	I compared both sensor one the raised hump is a bit higher.
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10-12-2018, 11:56 AM	#14
Efthreeoh General 19017 Rep 19,640 Posts Drives: The E90 + Z4 Coupe & Z3 R'ster Join Date: May 2012 Location: Virginia iTrader: (0)	Good Lord, I didn't mean to start an argument. The BMW TIS says not to lube the pins on the E9X chassis. The pins sit in a plastic guide sleeve, which requires no lube. I'm guessing the plastic is some type of ABS due the the high temps the brakes can generate. The plastic is self-lubing is the best way to describe it. Brake dust will gum up the lube if used. Like I said earlier, the only problem guide pins can have is if they are over-torqued and deform and become out of parallel with each other. Again, the torque is just 22 lb.-ft. People over torque them thinking they are part of the brake assembly and must need to be very tight. All they do is locate the caliper in the carrier, there is actually very little force acting on the thread faces, which is why only a small amount of torque is required. Last edited by Efthreeoh; 10-12-2018 at 10:36 PM..
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10-12-2018, 12:11 PM	#15
nsjames Brigadier General 2461 Rep 4,328 Posts Drives: 08 328xi Touring Join Date: May 2017 Location: ohio iTrader: (0)	even the carrier bolts don't need gorrilla torque. everything in the braking system is a bolt in shear. It just needs to be tight enough to not come out.
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