Rear brakes gone after 22,644 miles!

Thanks for posting this for everyone's benefit.

Attn Mods. Is there a way for this info to show up in the sticky post on TSB?

 

this is very interesting. i just hit 22,000 miles. no noticeable problems yet. are you heavy or light on the brakes? do you drive it hard and put it up wet, or are you a little ol' lady like me?

 

btw, i agree, they should reimburse you for the first work, all the best!

 

rear brakes, sound like the e-brake has been dragging...

Det,

I would not let the cost of one brake job sway you from the toyota camp. Ford has it own problems... the Cmax is far from trouble free...

 

I've been having some rear brake problems, some rotor scoring, and uneven contact on the inboard sides. Ended up replacing the pads (myself) at 46000 km.

I suspect pad installation procedure may be a problem. The rear caliper pistons have an integrated parking brake mechanism.

Every time the parking brake is applied, a lever attempts to rotate the piston. The piston has a raised cross pattern on the face in contact with the back pad, and that pad has a pin on it's back that is supposed to lock with the piston pattern, prevent the piston rotating.

What happens then, I'm still not 100% clear. There is a screw mechanism within the piston, connected to the parking brake's lever arm. That screw is wrapped with a spring, that (cleverly) only allows the screw to rotate in the direction causing the piston to protrude more.

I'm still not clear on how it manages to work, but what I'm suspecting:

If the pads are not firmly gripped by the caliper at initial assembly, when the parking brake is first applied, the piston may rotate on the back pad, shifting it's cross pattern out of proper alignment with the pad's pin, creating a chronic drag condition and uneven wear.

It seems it's paramount to pump the brake pedal multiple times at pad install, to ensure good contact, avoid this piston rotation. I took pictures of the pads when I first disassembled, never been touched since the factory, and you can see bevelling of the pin, as if there was some rotation onto a cross spoke.

Not sure what the solution is. With the present design, careful pad install technique, coupled with ongoing vigilance? And for Toyota, maybe a design change in future?

I've looked at pictures of the revised pads, compared to original (I believe the pads I purchased are the original design), the main difference I can see is an increase in the end bevel of the pads. Seems a somewhat stopgap measure to concentrate the braking pressure on a smaller area.

 

I would guess that perhaps your parking brake(s) were not releasing completely in order for you to wear the rear pads that quickly. What kind of gas mileage were you getting? With a "drag" like you must have had - I WOULD think your gas mileage would suffer. I have a 2010 and I just replaced all 4 rotors and all 8 pads and the only one that showed much wear (100,000 miles) was the left rear set of pads and, yes that parking brake had been "hanging up". After I replaced everything, I checked the rear wheels - both spun freely. I even lubed up the parking cables back there to help for any future problems.

 

Spinning the back wheels when raised is good periodic check. Another is to just reach in and feel the rotors on all four corners, after an extended run. Be careful, they can get hot.

Also, crawling under with a pit lamp (no raising of the car needed), you can just see a little bit of the inside rotor on the rear. There's about 1/8" gap between the splatter brakes baking plate and caliper, not much, to be sure. With a good light you can see if there's even wear: if there's a portion of the disk just showing rust you've got a problem.

Here's a shot of the inside face of a rear rotor (with the caliper removed) showing uneven the uneven wear I was getting:

 

My rear brake pads were changed in my 2010 Prius at 57,600 with pad kit: 04465-76010 so I wonder if this is also the wrong part as it was done in April 2012. Now at 105,073 they say I need new rear pads and rotors and that the rear caliper bridge is seizing up so that the left rear caliper bridge needs replacement. I don't get why this should be happening.

 

That's a decent set of miles, from your last brake job. But troubling that they're not just worn, more like seized, damaging the rotor. The integrated parking brake mechanism is a bit complicated, improper re-assembly can lead to problems. FWIW:

My bill for rear brake pads says:

PAD SET, BRAKE P/N: 04466-76012

Not sure what the difference is.

I also got new shims:

SHIM KIT, BRAKE P/N: 04946-47070