Uneven brake pad wear, replaced twice

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Jamdemos, Feb 18, 2020.

  1. Jamdemos

    Jamdemos Junior Member

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    2010 with 105,000 miles

    So this is somewhat driving me crazy, a friend and I replaced my brake pads in the rear after what I believe was the original pads at 100,000 miles.
    We did pads and rotors in the rears, about 5 months later, can’t remember the mileage I smelled burning pads and heat on the rear wheel. Both the pads on the rear were slanted with terrible uneven wear.
    Brough it to the shop and they claim the pads were installed incorrectly, this friend of mine has worked on cars his whole life and done hundreds of pad replacement and claims it’s almost impossible to instal them incorrectly. Claimed it was caliper not releasing or something, however the shop claims the calipers are fine and move freely, and the pads were installed incorrectly.

    So I took my friends advice and we replaced the pads, rotors and guide pins and guess what once again 5 or so months later I smell burning and the wheel is hot at the rear wheel, assuming the pads are again shot.

    This is driving me crazy at this point and don’t know what to do, he claims we should have replaced the whole caliper and that it’s almost impossible to install the pads incorrectly, but I’m hesitant to do this all again for the 3rd time, or do I take the advice of the shop that he installed the pads incorrectly. And go to them for new pads and rotors for the 3rd time. I’ll try and upload a picture of the pad from the first time, after 5 months it’s was super slanted, high on top and low on bottom

    thank you all in advance!
     

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  2. Ed Beaty

    Ed Beaty Active Member

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    Even for someone with lots of disc brake experience, Prius (rear especially) brakes present a few unusual critical tricky bits.

    Pretty sure the estimable Mendel Leisk will be along shortly to put you in the picture...
     
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  3. Siward

    Siward Member

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    Is it the rear outer pad that is wearing unevenly? To me, it looks like the caliper is pressing on the top of the outer brake pad causing the wear to slant. This happened to me about 2-3 times now. It seems to always happen after the winter months.

    I have replaced my rear brake pads three times now (once with the rotors). I use wagner thermoquiet brake pads + centric rotors.

    I replaced the caliper pins. That didn't work. Well, one original pin was rusted and later sanded.
    I replaced the caliper boots and bushings. This didn't work quite work.
    I sanded/filed down the outer brake pad ears. Not sure if this worked yet as I did this last spring.
    I bought 3M slicone lube to replace my prestone caliper lube. Not sure as I did this 2 years ago.
    I replaced one of the rear OEM calipers 3 months ago with a Raybestos Element3 caliper to see if it works better. I originally wanted to replace the caliper mounting bracket, but it costs as much as entire aftermarket caliper assembly.

    I will have an opportunity to check on my brakes the next time I swap tires. My next possible update is when winter is over.

    And yes, you have to make sure the piston "X" face clears the brake pad backing plate pin. This clearly wasn't my problem as the inner brake pad (which the piston is in contact with) is always wearing evenly. I always had uneven wear with the outer pad.

    I still have my old pads. I can also take pictures, but I don't want to get my hands dirty.
     
    #3 Siward, Feb 18, 2020
    Last edited: Feb 18, 2020
  4. Jamdemos

    Jamdemos Junior Member

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    That sounds like an absolute headache, hopefully that’s not the case with this situation. Just seems strange that everything was good up to 100,000 miles and now since the pads were replaced, they have worn funny twice in 8 months.
     
  5. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Gotta walk the dog first, but rest assured, there is an explanation. In the interim, some info attached. Look in particular for this:

    upload_2020-2-18_9-30-14.png

    It's imperative to reassemble with the piston oriented thus, and have it remain thus.
     

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  6. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    To this day I'm a little confused by the dynamics. Here's a pic of the pad backs, with these stubby pins flagged:

    upload_2020-2-18_10-0-39.png

    The caliper piston has to be oriented like an X (per previous pic I posted), so that those pins are between the raised spokes, the pattern on the piston face. Then the pads get even bearing.

    Applying the parking brake, I believe that piston will attempt to rotate. What stops it, hopefully, is that pin, in between the spokes.

    What's still puzzling to me: if the piston's managed to rotate, and the spoke has ridden up on the pin, why is the pad wear bevelled towards the edge opposite, without the pin (the edge with the "ears")?

    FWIW, I had the same issue, and similar wear. Also, on the inside face of the rotor, the pads seemed to be making next to no contact, as evidenced by the rusty zone:

    upload_2020-2-18_10-6-44.png

    My pad wear:

    upload_2020-2-18_10-7-44.png
    upload_2020-2-18_10-8-8.png
    It's a little subtle, but I believe the wear zone is on thumb side.

    Anyway:

    Your rotors likely have a rusty zone on the inside face. I would removed them (mark a wheel stud and the rotor hub to reinstall in same oritentation), and cleaned them up with steel wool or wire brush. They will still likely sound terrible after, for the first little while, but it helps. M8x1.25 x 1" long bolts screwed into threaded holes on rotor hub will help to bust them loose, if needed.

    Buy another set of pads, Toyota preferably. Prep them with the shims, thin coat of anti-seize on all faying surfaces, between pad back and shim, shim and caliper.

    Get the caliper piston orientation correct (per pic in previous post).

    Install everything. Pump the brake pedal multiple times. This helps to seat the pads solidly, and also avoids the car detecting excess brake pedal travel, throwing a code.

    Then reconnect 12 volt neg cable (it should be disconnected at the start, before any disassembly, to avoid possible activation of the brake pumps.)

    Do not apply parking brake.

    Lower the car. Take a short test drive. The brakes will likely make noise with every application, due to residual rust on rotor. On return, apply/release parking brake several times.

    Raise rear of car. Spin wheels. They should easily spin 2~3 revs with a good push.



    If they do, you should be ok. Brakes will continue to be noisy for the next day or two, but should clear up.
     
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  7. Jamdemos

    Jamdemos Junior Member

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    Thank you so much for such a complete explanation on this manner, so you’re assuming it was installed incorrectly, right? The friend who helped me is adamant that he did it right and that the calipers are shot, but that statistically seems off, how does it go 100,000 miles then we replace both rear pads/rotors and within 4,000 miles they both wear weird and drag.
    He’s saying replace calipers and everything but at this point it sounds like I just need new rotors and pads replaced correctly, assuming going to a shop they would be knowledgeable to do this correctly, after the first time the shop said they were installed wrong by the showing on how the pads wore
     
  8. ASRDogman

    ASRDogman Senior Member

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    Did you clean up ALL the matting surfaces where the pad metal touches the caliper?
    And did you use the brake paste/lube in those spots? Did you use the original plates from the
    original pads, or new ones, on the replacement pads?
    From what I understand you said the OUTER pad is wearing, NOT the inner?
     
  9. Jamdemos

    Jamdemos Junior Member

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    I unfortunately didn’t do much or the work as my friend did most of it, my limited exposure to maintained let him do it. I believe it was the outside pad but for some reason I feel like it may have been both inside and outside but maybe not. We did use the new plates and not the old ones, no lube or paste was used. Just can’t believe that he thinks the calipers are shot, when this happened to both sides at the same time after replacing, them the second time we did it we also did guide pins and this still happened 3,000 or so miles later. Tempted to trust the shop that said it was done wrong the first time and have then do pads and rotors for the third time.

    thank you again everyone for your advice
     
  10. ASRDogman

    ASRDogman Senior Member

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    I doubt it's the calipers.
    You should scan youtube and watch videos of how to do the rear pad replacement.
    It could be possible he has the pads switched. Inner pad on the outside, outer pad on the inside.
    Do you have the correct pads? If you get Toyota pads from Toyota, you should be good.

    But you may have to let Toyota do the job. And ask them to check it carefully and see what the problem is.
     
  11. Jamdemos

    Jamdemos Junior Member

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    ya being this the 3rd time I can’t afford mentally and financially to screw it up again. Could I have Toyota just do new pads, and not rotors, given that these have been dragging again intermittently, they seem to have some abnormal wear on the rotors also, but as long as it hasn’t worn past the pad should the rotors be fine still as they were new 3,000 miles ago? Replacing them 3 times seems also crazy, or am I wrong?
     
  12. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Did the guy who did your previous brake jobs know about the piston orientation?
     
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  13. ASRDogman

    ASRDogman Senior Member

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    Hard to tell without seeing the rotors....

     
  14. Jamdemos

    Jamdemos Junior Member

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    I highly doubt it as when he was doing it he did not mention it and didn’t seem concerned about any specific procedures, if it’s abnormal compared to 90% of other vehicles on the road AKA it’s specific to the Prius I doubt he knew. But then would a normal auto shop know other than Toyota?
     
  15. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    It caught me flat-footed, the first time I did a rear brake inspection. 6 months later I noticed scoring on the outside of face of the rotors. I recalled the wheels seemed draggy when I'd buttoned everything up, thought it would smooth out with time.

    Nope: jacked up the rear found it was still hard to turn the wheels. Took everything apart, took some pics (posted above). Read up on the piston orientation requirement, purchased new pads, took everything apart again, took off the rotors and steel wooled the worst of the rust off the inside face.

    Then put everything together with new pads, paying VERY close attention to the piston orientation, pumped the brake pedal, firmed everything up, and didn't touch the parking brake. Tested the wheel spin, seemed pretty good. Took it for a test drive, easy on the brakes: lordy you knew when the brakes were being applied, very noisy. Due to that rusty, untouched zone on the inside face of the rotor.

    Got back, depressed/released the parking brake, raised the rear, and confirmed the wheels continued to spin pretty good.

    A few days later the noise from the brakes was hard to hear. A month later perfectly quiet, and the scoring I'd first noticed on the front face of rotors was gone as well.
     
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  16. Jamdemos

    Jamdemos Junior Member

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    Mendel thank you again for the detailed explanation, being that this has happened twice in 6,000 miles or so with complete replacement it seems that maybe the installation truly is the problem. I’ll be taking it to a shop now for the 3rd pad/rotor replacement, should I explain this process to them making sure they understand. Obviously I would think that’s over board to tell a competent auto shop that there a “trick” to replacing these brakes. But if this one step of orientating the piston is crucial in preventing what is happening then it needs explaining I guess. I just hope going to a competent auto shop and paying the $400 they want for the pads and rotors it’ll be done correctly this time and I can move past this break nightmare.
     
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  17. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    I'd never heard of this before, but then all our previous cars had rear drum brakes. It's due to the integrated parking brake, and the particular design. There is another approach that utilizes a mini-drum brake, built into the rear rotor; the Prius v uses this approach. our daughter's Honda Pilot had the mini-drum too.

    Yeah, if you've got a finicky, somewhat unusual design, that can be messed up if you're not on your toes, maybe that's not a good design...
     
  18. jzchen

    jzchen Senior Member

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    Now you have the proper instructions. Have your friend do it a third time, this time with the directions kindly shared by Mendel. (My humble opinion)....

    moto g(7) power ?
     
  19. ChapmanF

    ChapmanF Senior Member

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    One thing to be aware of: heat can be the enemy of the rubber parts. The rubber seal inside the caliper plays an important role in retracting the piston when you are done braking.

    There is a possibility that the rubber was originally fine, and there wasn't any problem except the pad installation, but with the pads constantly dragging, the brake may have gotten hot enough for long enough that now there is a cooked rubber seal added into the picture. If that has happened, even with the pads installed right, the brakes may continue to drag.

    It's possible with a dial indicator to check that the caliper pistons have good, positive retraction (I've measured around 0.3 mm for a good Prius front caliper, but I haven't measured a rear).

    If the retraction is shot, the rubber kit for caliper rebuilding is not much money (though, unlike a simple pad replacement, you have to not mind brake fluid on your fingers, and be able to bleed the system when done).
     
  20. Jamdemos

    Jamdemos Junior Member

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    I am extremely grateful for all the info Mendel has given, however given that my friend is still adamant it was installed correctly and that something else AKA the calipers must be shot. I’m going to bring it to Toyota at this point just to rest assured it will be done correctly, they’ll do an inspection first and go from there. The friend I had do it twice is extremely knowledgeable with vehicle maintenance, but if there is a special order of operations for this vehicle that he’s missing, doing it a 3rd time isn’t going to solve anything.
    Thank you all again, hopefully this solves the problem, and doesn’t open a can of worms for other issues that will arise.
     
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