Rear brake bias - wearing rear pads VERY fast

[mooch91]

Hi all,

Looking to see if you can help me identify why I'm wearing my rear brakes VERY fast on my 2006 4Runner. After about 10K, my pads are better than half worn, probably closer to 2/3.

Replaced rotors, pads, and calipers all the way around, a little over a year and 10K miles ago. I used Napa parts and selected their more "premium" option for the pads and rotors specifically ("Silentguard" pads). I also flushed the brake fluid out all the way around. When I got done, the pedal felt stiff, but I attributed that to the fact that the old components, including the calipers, were shot after 240K miles. I have a couple of 5th gens as well, and every time I'd jump back in to the 4th gen, it would take some time to get used to the brakes so I wasn't lurching forward when stopping.

Now 10K miles later, the rears are worn. Equally on both sides, and equally on the inboard and outboard pads. I'm also feeling pulsation and noticing the front rotors don't look as smooth as I'd expect. I suspect I've got a rear bias on braking for some reason.

I'm going to tear into it tomorrow, but I'd appreciate any thoughts for things I should be looking for beyond sticky calipers or poor quality pads. Anything in particular that could cause the rear brake bias and accelerated wear?

Yaw sensor doesn't affect the brake bias, does it?

Thanks!

 

[SocalSam]

Book answer is sticky master cylinder.

 

[Drcoffee]

Both rears equally worn, I would look at the flex hose forward of the rear axle. If the hose is swollen or hard its probably rusted closed. The hose has steel braiding in the rubber. If the rear brakes are working harder, the fronts will get less use. And since its happening to both R and L, thats the common point of failure. Master Cyl could also be failing but you said the brakes are hard. Failed master would be a soft pedal. Pulsing could be warped rotors caused by dragging pads. Worn wheel bearings.
If I had to guess, its the flex hose in front of the rear axle.

 

[Drcoffee]

Does the 2006 have a brake booster? The rear has a separate pump. Maybe the vacuum booster is failed

 

[AuSeeker]

Does the 2006 have a brake booster? The rear has a separate pump. Maybe the vacuum booster is failed

No vacuum brake boosters on 4th Gens and onwards(also maybe the last year or two of the 3rd Gens), all power assist and ABS functions for the fronts and rear are done using the electric motor/pump and accumulator attached to the master cylinder.

 

[Runnin on E]

Frozen calipers on the front? Sounds like the rears are working just fine.

 

[BackOff]

This happened to me a couple years back, after i did the brakes.
For me it was the front pads, the ends were hitting the caliper so they were just basicly jamed in and not moving so the rears were doing all the work.

Swapped with akebono and made sure that the pads were free floating and not jamed, fixed!

 

[Drcoffee]

Chances both fronts seized the same are low. There should be pronounced pull to the left or right.