Brakes wearing unevenly

Brake fluid is hygroscopic and collects water (moisture).
The fluid will be compressed during braking und will heat up under this pressure. At long enough downhill passages the heat will be high enough to vaporize the water contained in the fluid. While the fluid is incompressible, the vapor is. That means the brake pressure will decrease rapidly at boiling point and then the brake force, too! (Boiling point of new brake fluid is much higher than the b.p. of water, it won't vaporize itself.)

At least the front brake pistons of the gen 2 are made of plastics, so they won't rust. But the rear pistons will rust over the time. The will press the pads at the disks/drums, but they won't release proper, resulting in more wear.

 

I would not worry about that because the brake fluid typically is not subjected to the same temperature extremes as a normal vehicle, as most of the braking effort is via regen vs. the friction brakes.

 

But moisture is still absorbed into the brake fluid. And on emergency braking (basically) all braking just happens with friction brakes. And bad brake fluid can cause other problems too.

And if you have 10 year old car with brake bleeder that have never been opened that has driven on salted roads it’s super hard to open the bleeders when/if you need to.

 

Toyota Canada's seen fit to include brake fluid change in the schedule, for all cars they sell, from 2012 onward. IIRC it's 36 months or 48K kms (30K miles).

I'm a little nonplussed, by the disinterest in following the Toyota proscribed brake maintenance interval. I appreciate it's somewhat overkill, but maybe look at it as akin to getting your teeth scaled every 6 months, vs the alternative?

Tri-yearly or 30K miles is certainly not onerous, for decent brake inspection. I wonder what's the root of the malaise: dealerships are downplaying the need for it, too busy pushing fuel injector cleaning and other crap?

 

No just stating the fact.

I went to the dealer to have my brake fluid changed. The brakes work fine. I was told they would not change the fluid as it has caused many ABS units to fail on a G2. They do not recommend having it changed anywhere. Unless as Pat said the ABS is replaced also.
Pads look good as do the rotors. What would you have me do?

Cue Honda reference.

 

My wife and I managed to bumble through a brake fluid change, in about an hour, with the section from the Repair Manual, and watching @NutzAboutBolts video. Maybe easier with 3rd gen, not sure.

 

I would think that such a difference is most likely just luck of the draw. One slider pin got more jammed up than the other slider pin due to corrosion and loss of lubricant. Other thought is that generally the left side of the car is slightly heaver than the right for most driving (due to having a driver only in the car) and therefore the brake gets worked just a touch harder than the other side (I can't confirm this - just speculating).

This effect can certainly be seen on cars' tires that have never been rotated at the end of their life - the driver's side front tire will be bald, the passenger's side will have a mm or two left, and the rears will still be at 40%.

 

That was already answered at the first reply to this tread. That side just happened to seize. After it’s seized it wears fast. One side will always seize before the other. Unless you service brakes often enough (if you do then they wouldn’t seize).

 

Wow, that's one done pad:

 

I have a brake caliper theory that I cant' prove. Here it goes. As the brakes wear the piston travels out of the piston bore. After it extends to a point where it doesn't move as well because there isn't enough material to keep it in alignment. Here is an example, you take two pipes, one larger than the other but the smaller one will fit inside the other one. Start separating them and when they are close to being separated try to push them back together and they bind.

Back to brake pads, this would happen about the time your pads needed changing.

 

The piston extension is only about 8 mm though. But yeah, could make the difference.

 

Yeah, and the small colored area indicates, that very much heat occurred at least one time. Hopefully it didn't affected the piston. (The front ones are made of some plastic.)
But if the piston moved back in for enough space for the new disk and pads there shouldn't be any problem, I think.

 

When changing wheels, you can have a look at the pads thickness. And if you have a micrometer screw gauge, you can easily check/compare the disks, too.

 

Every time I remove my wheels I always look at brake pads thickness and the condition of my rotors.
Aftermarket rotors are cheap, I just replace them. I have never used a micrometer to check rotor thickness but have checked run out but not on a prius.
I have only ever needed to turn rotors twice and the second time they were worse than before I had them done
I like new ones.