Brakes, Rotors & Pads

The cube has different nub styles, but pretty much any of them will work.

It screws in thus cus it's got incorporated brake mechanism. My brain hurts every time I try to explain it, let alone understand it myself. It has a tricky accommodation, for brake pad wear, the parking brake mechanism, and so on. There's a spring inside that allows rotation in one direction only. And the pin on the back of pad prevents the piston from rotating, when assembled. Or at least it's supposed to: it's when the pin manages to ride up on a spoke that problems arise. Maybe NutzAboutBolts, Chap or CR94 can jump in, lol.

 

What would cause the pin to ride up on a spoke? I ask this because I replaced pads (and rotors) about 2000 miles ago and now those on the driver's side are worn out! Also the wear is not even -- the leading (front) edge of the pad is worn less than the trailing (rear) edge of that pad. As I understand it the pin on the pad should be in one of the four recessed areas of the calper piston. I also assumed that this pin woudl engage the raised area of the piston under some circumstance and this is how the piston would be screwed out to adjust for pad wear.

 

I believe the pin will ride up on a spoke if you apply parking brake before the brake pads have been seated. After assembly you want to push multiple times in brakes, maybe a short test drive, only then apply parking brake.

 

Replace pads as needed. Rotor ONLY need replacement once they wear to the point they can't be turned anymore. Turning is a way they shave off metal to make the rotor straight again...often needed only if your rotors become warped.

 

Well I finally got around to replacing the rear pads at 55,000 miles.The outside pad on the right rear was wearing uneven enough for the metal backplate to hit the rotor for a while. Some damage, but will ok as the pads wear in. I know I waited way too long. So I also inspected and replaced the left rear? It also had uneven wear but not as bad as the right, and not touching the disc. I think I got lucky with the inside pad pin seating properly in between the raised spokes of the rotating piston. I had forgotten to make sure the pin was between the high points, but I never hit the parking brake until after I turned on the car, hit the brakes a few times and then drove the car and tested the brakes many times before I parked the car and engaged the parking brake. I also re-greased all the sliders all the way around. They were lacking in grease. I sure hope,the bad uneven wear on the rears was a result of sliders sticking. I will raise the rear in a couple of days to see how the wheels spin.

On the photo below, The one on the right is off the right side, the left one is off the left side. You can see the uneven where. I bought the car new and there was never any service to the brakes until I noticed the pad wear issue. I wonder what could have caused this. But I hope I have solved the proble.


Again Tks to all who provided the instructions and the you tube videos. They were very helpful and saved me from screwing up too bad. I used a pair of blunt needle nose plyers to screw in the piston.
By the way I never disconnected the battery. Instead I unlocked the car and put the keys back in the house and told everyone not to touch the door handles. That part went well and I did not lose my memories.

 

That wear is grossly uneven. My hunch, again: backing plate pin riding up on the piston spoke pattern. How do the pins look on the inside pads? Bevelled tops?

If you've got fresh pads in, and you applied the brakes multiple times before using parking brake, and with the rear wheels off the ground they're spinning fairly easily, you're out of the woods.

 

See post # 6...pad measurements.

That answers one of the OP's questions.

Brake fluid flush at that time would be my recommendation.

Plus, as many on this forum have pointed out, inspect and lube or replace those pads pins to avoid the pads hanging up on them.

Now rotor wear.

If one is gouged, OK replace in axle sets IMO.

As for wear , if the rotor as a "lip" caused by wear from the pads at the out circumference of the rotor then yes replace.

If rotor is wrapped, or contains waves in the metal surface that the pads contacts, replace.
(One can measure with a caliper and run out gauge tool.)

I personally am not in favor of turning rotors as this process removes metal and reduces the rotors capacity to remain wrap resistant. However, many do turn a rotor with no adverse effects.

Lastly, as for when you need brakes, some get over 100K in mileage some get 50K. It all depends.

Good luck with your brake job.

 

Turning rotors and drums is perfectly safe. Like brake pads, they are made with a minimum thickness rating. Once they are that thin, you must replace them. There's enough excess to turn them a few times, but the only real reason to turn a rotor is for warping or serious gouges that turning would "fix". It doesn't affect brake performance because the pads "self adjust" to work with the disc's thickness. So long as that minimum thickness is maintained, there's no danger of structural failure or heat issues one needs to worry about.

 

Lack of lube on the caliper pins, or the pad contact points, brake fluid issues, might cause one pad to wear faster than the other, but doesn't explain the extremely beveled wear. And with this happening with the rear brakes, the smoking gun is the parking brake system, that back of pad locator pin riding up on the caliper piston spoke. That will cause just this sort of wear.

This is how they look new:



And if they've been riding up on the spokes, skewing the pads, causing uneven application:

 

To confirm, the bad pads were on the outside. The inside pads pin that engages the piston looked fine. I had not touched the brakes on this car as it was new. I just noticed the noise and the grove developing on the outer edge of the right rotor. I hate to say how bad it is but I am letting it go for now and see how the new pads conform to the disc and see if the pads show that severe uneven wear again. (The rotors do not appear to be warped and I saw no heat signature on the rotors either). If so then I will need to bring it in and get a new rotor. Assuming they fix it properly. But heck, from new it was not right, I just wish I had noticed it earlier to bring it to their attention under warranty. But having had toyotas before, I never thought to inspect a new car in that way.

Yea I think the piston set fine on the inside pad pin. The car rolls freely and the car brakes evenly. But later this week I will jack up the rear and verify the free spinning of the wheels. But to be fair, it seemed to work fine before I discovered the bad pad and rotor. I am stumped as to why this happened while the car ran fine.

If I feel extra patient, I will bring the pads over to the local toyota dealer and ask if they have any incite. But I'm guessing they won't.

By the way, Tks again for all the help from you guys. I really appreciate the incite.

 

My experience usually indicates a misaligned caliper, but again, that should affect interior and exterior pads...one would think. Their install should be "idiot proof" but sometimes the factory screws up and doesn't properly align the parts in the wheel hub assembly.

 

Completed the first fluid change and pin lube at 144k. Huge thank you to NutzAboutBolts for the how to videos.

Pad thickness was around 6.5mm except for the front passenger pads. Inner pad is showing faster wear at around 5.00mm. Hopefully the pin lube will slow this down. Otherwise the rotors may rust away before the pads wear out.

 

Inner pad wearing faster does seem symptomatic of caliper pin lube deteriorating: with the caliper reluctant to shift laterally there'll be more push on the inner pad. Looks like you caught it though. Was this the first time the pins were lubed? 144,000 miles at that much pad left is astounding, btw.

If you want to assess the rotor's well being, ie: thickness and parallelism, a 0~25 mm micrometer and a dial indicator with magnetic base (both around $25~35) are fun to try. The rotor spec's are in here:

 

First time pins were lubed. Miles are 99% highway and a lot of forced regen braking on the off ramps. Suspect city miles would never see this little wear. Side by side comparison of old fluid on left and new on right below.

 

That fluid looks good, first change I assume?

I just did brake fluid change on ours, way sooner, and the dealership did it also, 3 years back. This was around 6 years and 64,000 km's. I didn't think to do comparison pic. The old fluid looked kinda golden even then, maybe it's time as much as distance? The Canadian schedules now say 3 years or 48,000 km for the fluid.

And yeah, even though I have the Repair Manual instruction, @NutzAboutBolts was invaluable, all the hands-on tips, and just that it says "you can do this".