Rear brake wear

[The Car Stereo Company]

Wow, what are you doing to burn thru brakes like that?!

i was testing tires for a tire manufacturer. and then theres my normal offroad driving..... pretty much the same difference. heres one of my rotors after a night drive in the mountains. all 4 looked like this 3-4 times a week sometimes

 

[FordTechOne]

Here's the description of the ABS proportioning per the Workshop Manual.

Electronic Brake Force Distribution (EBD)

On initial application of the brake pedal, full pressure is applied to the rear brakes. The ABS module uses wheel speed sensor inputs to evaluate rear wheel slip. Once the rear wheel slip exceeds a predetermined threshold, the ABS module commands the HCU to close the appropriate isolation valves to hold the rear brake pressure constant while allowing the front brake pressure to build. This creates a balanced braking condition between the front and rear wheels. If the rear wheel slip continues and exceeds a second predetermined threshold, the ABS module commands the HCU to open the dump valves to decrease the rear brake pressure and allow the rear wheels to recover. A slight bump sensation may be felt in the brake pedal when EBD is active. If the ABS is disabled due to Diagnostic Trouble Codes (DTCs) being present in the ABS module, EBD continues to function unless the Diagnostic Trouble Codes (DTCs) are for wheel speed sensors or the HCU solenoid valves. When EBD is disabled, the ABS warning indicator, the red brake warning indicator and traction control indicator illuminate.

 

[Mister Pinky]

It is not at all unusual for the rear brakes to wear more quickly than the front brakes on late model vehicles. To balance out the braking and counter front end dive, the ABS module proportions a significant amount of brake pressure to the rear. The strategy is much more aggressive than old school mechanical metering and proportioning valves, which in many cases would have the rear drum brakes last multiple times longer than the front, as the rear was doing very little actual braking.

I first saw this on BMWs. They were designed to bias in the rear brakes more to alleviate nose dive under heavy braking which in turn preserved handling in high performance maneuvers.

Also of note, with the debut of the 2008 GMT900 1500 trucks, GM, with all their fantastic engineering knowledge, elected to put rear drum brakes on the truck because the rear disc brakes on the previous generation 1500 were constantly “warping”.

Service techs would later note that the rear brakes rarely ever needed replacement on the GMT900s. In my own ownership experience, I found this was because the shoes were rarely in good adjustment with the drum. I had to resort to adjusting the rears with every oil change, and the difference in the brake pedal was noticeable.

So imagine, for the average driver who knows nothing about their vehicle, how many cars and trucks were driving around back then without full braking capacity.

 

[Ryan C]

Thanks @FordTechOne for the detailed information. In light of the processes you've described, do you feel as though the wear rates I've experienced is within an acceptable range, or does it suggest there is something wrong with the system (mechanically, or perhaps because of dirt, mud, etc.)?

 

[fordraptorfun]

I had the same issue of rear fading early, good to know why.

I found it really hard to find OEM replacement PNs for the 2019/20 with electronic e-brake. Here’s what I used in case you’re interested. Info came from local dealer


KL3Z-2001-A Front Pads
JL3Z-2C026-D Rear Rotor Assembly
JL3Z-1125-B Front Rotor Assembly
KL3Z-2200-A Rear Pads

 

[Jughead]

13,000 miles? Thats crazy.

 

[Zeusmotorworks]

Maybe not for his type/frequent use of the components above 99% of folks.

 

[Miker397]

My oem rear pads on my 17 raptor were sub 1mm driver rear and 2.5mm passenger rear over the first 35k miles I drove the truck (normal road driving, some towing, nothing extreme except a single day at the sand dunes). I'm now at 46k miles, so 11k miles later, and the driver rear is back at 1mm on the inner pad but the front original pads are still at 6mm and the passenger rear is at 6mm now. WTF is going on? Dealership said the caliper isn't sticking, no leaks, and everything looks normal. It's not a big deal for me to pad slap a $40 pad on, but there is no way I should have to do this every 10k miles. Any thoughts?

 

[amREADY]

Here's the description of the ABS proportioning per the Workshop Manual.

Electronic Brake Force Distribution (EBD)

On initial application of the brake pedal, full pressure is applied to the rear brakes. The ABS module uses wheel speed sensor inputs to evaluate rear wheel slip. Once the rear wheel slip exceeds a predetermined threshold, the ABS module commands the HCU to close the appropriate isolation valves to hold the rear brake pressure constant while allowing the front brake pressure to build. This creates a balanced braking condition between the front and rear wheels. If the rear wheel slip continues and exceeds a second predetermined threshold, the ABS module commands the HCU to open the dump valves to decrease the rear brake pressure and allow the rear wheels to recover. A slight bump sensation may be felt in the brake pedal when EBD is active. If the ABS is disabled due to Diagnostic Trouble Codes (DTCs) being present in the ABS module, EBD continues to function unless the Diagnostic Trouble Codes (DTCs) are for wheel speed sensors or the HCU solenoid valves. When EBD is disabled, the ABS warning indicator, the red brake warning indicator and traction control indicator illuminate.

Thanks for this (and all your other contributions). I've sure found them helpful over the years.
In addition to the EBD rear bias, the VSC and traction control can get really busy on those back brakes from what I understand. I was getting what I thought was premature wear on my 2019 rears that caused me a lot of concern, as I was expecting the opposite. After some googling and foruming, I suspected that the wet road, snow, offroading was causing my traction control to be too busy. Unless the snow is deep, I don't generally click it off for on-road driving, but I made a point of taking it off more often when offroad and it slowed the rear brake wear. I still wear rear brakes maybe 2x faster than fronts, but this made a big difference.

Other info:
I think that 4x4 modes detune the traction control to a degree. I will drive dirt/gravel roads in Normal mode, 4A often if I'm not getting after it and conditions don't require 4WD.
If it's quite slippery in snow or offroad, I'll use 4WD over 4A to reduce the clutching? the 4A needs to do. It also provides a more positive feel as there is no micro slip delay to engaging more front wheels. This might also have a benefit of less brake wear as per above discussion unless you turn the nannies off manually.
I'd rather wear brakes vs. be in the ditch. In other words, I don't just turn VSC or traction control off at the drop of a hat. Maybe not cool to rely on nannies in some situations, but I'm secure enough to say they help in some situations.
I drive a lot of steep mountains and use gearing and give the brakes regular rests vs. riding them down the steeps. This saves the brakes considerably.