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Inside brake pads seized

Discussion in 'Model S: Driving Dynamics' started by scottm, Apr 26, 2016.

  1. scottm

    scottm Active Member

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    #1 scottm, Apr 26, 2016
    Last edited: Apr 26, 2016
    Using the brakes starting to show signs of "warped rotors" pulsations on pedal.

    I went for some hard driving and stopping cycles to heat the brakes thoroughly and allow to cool down for miles before stopping. Made it a little better. But I noticed hard braking was not really stopping the car as quickly as it should... Turns out this attempt to burn off crud on disc was a stupid redneck approach ... I should have inspected first.

    At tire change over to summers, I took off front caliper. I've never had the caliper off the car yet in 50,000 km. Why should I, brake pads never wear on this car... right !?

    I found the inside brake pad firmly encrusted into the caliper and in no way was moving with pedal presses. The backside of the rotor / disc was not shiny and bright and smoothly worn. It was blotchy and mottled and looked like it hadn't been used in a while.

    So I repeated this, and visited each corner of the car. 3 out of 4 inside pads were seized. 1 on the rear looked like it might have been doing some braking work. All pads around the car had much thickness left to them. As expected, regen saves the wear. Rotors measured over their stated thickness for replacements. One rotor when spun on-car did have a very slight warp where the brake pad touched and created some friction for 1/4 of the rotation but spun freely for the remainder of the rotation. Not enough to cause me worry.

    I knocked all inner pads out of their calipers using combinations of Moovit parts loosening spray, hammer and punch, pry bar.. being careful (mostly) to not score any of the rubber surroundings of the brake pistons in the caliper, or do other damage. I filed down the crud and rust on the caliper where pad sides are supposed to move, and filed the pad edges... to make some mechanical clearance again so they could move. I used a light touch of anti-seize compound on the filed areas... and when for drive.

    The "warped rotor" feeling is gone. Smooth stops. And stops in much shorter distances again... Like new. As it should.

    I have made the vow to pull calipers and check at EACH SEASONAL TIRE CHANGE OVER... This looks like a design problem / prone in my area with lots of winter and road grime conditions. This is one of those things that slowly creeps up on you ever so gradually reducing the braking effectiveness that you just 'get used to it' and brain registers as the new normal, without suspecting anything.

    I wouldn't expect the Tesla annual service to catch this, they didn't in my case. I was just glad it was something I can do for myself by wrenching on this car. I don't mind that.

    It was stupid to do hard braking trials without inspecting this first, because that was sure to heat just one side of the rotor / disc .. a recipe for creating warpage. So don't do that.
     
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  2. Spurkey

    Spurkey P04251

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    I thought Tesla at least pulled the pads out during the annual service to inspect them, with the open-back calipers it's pretty easy unless the pad is stuck which should then indicate to Tesla there's a problem. :) Did you try getting the pads out through the back, or were they so stuck in there you had to take the caliper off? I've checked my pads because I've had similar concerns, Edmonton is pretty bad for winter grit, but I've not had any problems like this yet. I'll definitely keep an eye out.
     
  3. scottm

    scottm Active Member

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    #3 scottm, Apr 26, 2016
    Last edited: Apr 26, 2016
    I don't think Tesla pulls pads for an inspect, they might look at pad thickness with brake calipers still on car. Seized pads have the side-effect of having really good wear characteristics - almost like new! :p So they'd get a "pass".

    Yup, Edmonton is where I drive every day. Pads were so stuck it needed a lot of work to free them out. No way could the seized pads have been freed with calipers still on the car. They were totally crusted in and looked to be "one with the caliper" itself, no visible seam.

    I think the caliper design doesn't seem to allow crud to fall out very easily from around the sides of the pad, it seems to invite holding crud. Just no clear path for stuff to fall out. Brembo probably could have thought a little more on ways to allow stuff to find its way out... But it also probably has something to do with not using the brakes very much on Tesla. A non-rolling stone does gather moss.

    Now that pads are moving free and nicely... tell me how I'd do a quick check without removing the caliper to know that they haven't seized.

    I am now familiar with the two knock-out pins and spring clip of caliper design. I'd like to skip the caliper removal step if there's an operating check I can do while calipers are still on-car to know the pads have not seized.

    Maybe I could slip a piece of paper between pad and rotor and apply brakes to see if it grips the paper... repeat for each pad.. wonder if that would be enough?

    Could I un-spring the clip and do as you say, try sliding a pad out? By the way people, that retaining spring is strong! TIP: knock out one pin (punch it out) and then the spring flops out ... much easier than trying to fold and pinch the spring out ... which was my first attempt.
     
  4. Tennisballer

    Tennisballer Member

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    I suggest that you use a tool such as a screwdriver or some such and depress the caliper piston this will allow you to see if th e pads move freely. You would need the wheels off which does not sound like a problem. The tool will be used to pry the pad back pushing in the piston on the caliper. It will be obvious if it is bound up.

    VERY IMPORTANT after depressing the caliper piston you will need to pump the brake pedal in order to not cause a crash the gap created must be taken up afterwards.
     
  5. scottm

    scottm Active Member

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    #5 scottm, Oct 11, 2016
    Last edited: Oct 11, 2016
    So I wanted to show you the damage I had done to a disc pad on the front while trying to un-stuck it from the caliper.

    See the chunk that is missing in one corner?... yup.. that's what jamming a screwdriver into the pad does. I was actually shocked at how soft pads really are.

    Been running this way for several months. Finally got around to replacing it.. with some Bosch pads, hence the paper in the background.

    Even tho I damaged just one pad... I replaced all pads to be the same across the front of the car. Besides, can't buy just "1" pad.

    IMG_9397.JPG
     
  6. scottm

    scottm Active Member

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    #6 scottm, Oct 11, 2016
    Last edited: Oct 11, 2016
    Here's the Bosch pads, how they compare to Tesla OE.

    I put a couple thousand km on them already on a road trip. Yah, they stop the car just as well as the OE pads. Can't tell the difference in stopping power. ... who uses brakes anyway?

    I had about 80,000 km on these pads... they were not appreciably worn or reduced in thickness much. Maybe a millimeter or two. Life would be the shits if you were a brake pad salesman and all your customers drove Teslas. This is just not a wear item on the Model S.. unless you do something stupid and damage one trying to unseize it.

    Things I notice different about these Bosch.. the metal backing the pad material is a tad thinner, it's probably not as high quality steel either. The anti-noise friction plate on the Tesla pads extend over the holes where the locating pins go, and are more generously sized.. Maybe keeps them from moving too far from intended position. The clip locations on the friction plate are in different places. The brake pad material of the Bosch is chamferred on the leading and trailing edges. Therefore, a slightly smaller contact patch than OE. Over time, the contact patch grows. But that will be in like, 20 years.

    IMG_9394.JPG
    IMG_9395.JPG
     
  7. scottm

    scottm Active Member

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    #7 scottm, Oct 11, 2016
    Last edited: Oct 11, 2016
    Here's the only tools you'll need to replace front pads. I grabbed a "toy" hammer (dollar store), and blunted a common nail on the grinder for a half second to get the point off it, to use as a punch.

    Seriously easy to do: Jack car up (jack mode please!) Take the tire off. Knock a pin out of the caliper with a blunted nail. Take the spring clip out. Knock the other pin out.

    Pads slide out the side of the caliper. IF THEY'RE NOT SEIZED :mad:

    Slide the new pads in. Reverse the process with the pins and spring clip. You might have to compress the brake pistons back into the caliper a bit if the old pads are worn quite a bit thinner than the new thick pads going in.

    IMG_9393.JPG
     
  8. Doug_G

    Doug_G Lead Moderator

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    Weird. My car has been through four Ottawa winters now, and nothing like this has ever happened. I dare say the conditions here are a lot worse - gobs of salt everywhere.
     
  9. scottm

    scottm Active Member

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    It's not the salt, it's the grit they put on roads here with the salt.

    Salt melts away, grit sticks in calipers.
     

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