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Brake caliper spring clip broke during extreme cold

Discussion in 'Model S: Interior & Exterior' started by JakeP, Apr 10, 2014.

  1. JakeP

    JakeP S P4996 / X P6028

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    So I had an interesting and mysterious series of events occur this year, which was finally resolved yesterday, based on a random link I received from Newscutter.

    Back in January, we had a really cold spell. As I was parking my car one day, I found this metal piece in my driveway on top of the fresh snow, in a spot where only my Model S would have driven. I had not used the snowblower or anything yet, so I am wondered if it may have fallen off the Tesla? It was in a spot where I turn the wheel all the way left or right to get into or out of my garage at 90-degrees to the driveway. I can’t think of anything else that could have deposited it there, except an aircraft overhead! It was covered in black liquid, but was not oily or greasy. It is clearly snapped right off of a bigger piece of metal, perhaps due to the cold temps.

    I immediately emailed these pics to my Service Center, and asked if the piece could belong to anything on the underside of the Tesla. They promptly responded that it didn't look familiar as a piece of the undercarriage or suspension, and they looked under a car on the rack and didn't see anything similar.

    Tesla Part 1.JPG Tesla Part 2.JPG

    I wrote it off as possibly a piece of brass from some exterior light fixtures I had replaced over the summer, which somehow must have been flung there from alongside the house or the garage wall during some shoveling. But it still bugged me because it was on *fresh* snow, and seemed too heavy to have been lifted by winds.

    My car went in for its annual service shortly thereafter where a bunch of items were covered, and I never experienced any issues.

    Then yesterday Newscutter sent this link along with a bunch of other helpful links (TMC inlcuded, of course) to some prospective Tesla buyers we had met and given some impromptu test drives to earlier that day (Tesla grins all around, of course).

    2012 Tesla Model S Signature Performance Suspension Walkaround

    I was scrolling through those pics of the underside, and there were two pics of exactly my broken piece of metal...the caliper spring clip, on top of the brake calipers!

    Caliper_fe_9171215_600.jpg Caliper_fe_9171219_600.jpg

    We had never had any issues in the months since, and Newscutter suggested I go back and look at my annual service records, to see if they had replaced the caliper spring clip. Item #1 was the 12 month inspection, including mention of the brake pads, nothing mentioned except the pad widths. Some other mention of the rotor discoloration inside the pad radius, still nothing about the clips. But sure enough, the very last item #29 said: “Technician noted on inspection front left brake caliper spring missing, replaced left front caliper spring.” I don't know why I never connected the two. Having never changed my own brake pads, I was envisioning a coiled spring, not a flat metal clip spring. Now I know better, and after several months, the mystery is solved!

    In retrospect, I am wondering if perhaps the strain of the brake pads being frozen onto the rotors after washing it in the garage may have cause the breakage on the clip, perhaps exacerbated by the cold temps.
     
  2. wycolo

    wycolo Active Member

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    The function of such a clip is simply to maintain a slight pressure on the 2 brake pads at all times to minimize clunking and chatter. The 2 pads are always somewhat loose which allows them to be pressed hard (and then released) between the braking surface (rotor) and the caliper hydraulic piston without jamming, which might occur if the clearances were tighter. Ice can build up in this area that could cause this clip to break in two when the brake was activated or the rotor started to turn. Likely that part suffered stress sometime prior to failure. A rare event and certainly of little consequence since the brake system can function properly without any clips, albeit clunkier and more chattery.

    Nice sleuthing on your part!
    --
     
  3. JakeP

    JakeP S P4996 / X P6028

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    Thanks Wycolo! That definitely fits nicely as for a theory of ice and cold stressing the metal to failure. Glad to hear it wasn't a safety issue either, between the time it happened and when the Service Center spotted it and replaced the missing clip.
     
  4. JakeP

    JakeP S P4996 / X P6028

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    Wow, my service center just emailed and said that Engineering contacted them to see if I still had the broken clip piece (I do), and if I could send it in. How utterly fantastic is Tesla Motors Corporation? Time to buy more stock, I think. I had sent an email with these pics in to the service center a day or so prior to posting this here on TMC, so I don't know which triggered the response from Engineering. But on the likelihood that it was this post, thank you Engineering!!!

    Sending the piece in today along with specific dates and data...piece found on driveway (and likely broke) on Jan 3, 2014. Temps in my zip code ranged from 2F to 14F that day. I often wash or rinse the car in the attached garage, so rapid cold exposure and sudden ice formation and expansion may well have caused the stress fracturing in the metal, as surmised by Wycolo above.
     
  5. AudubonB

    AudubonB Mild-mannered Moderator Lord Vetinari*

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    Another tip o' the hat for your forensic work, Jake. One caveat, however: from my perspective, temperatures around the 0ºF mark are what we call a warm spring day. It is highly unlikely that a metal part would have been fatigued from exposure to those temperatures and nothing else. A bad casting? Sure, could be. Completely encased in ice and then called upon to move? As well. But if it truly were all - or mostly - temperature related....well, then, it's time Tesla abandoned use of that so-called cold-weather testing site they're using in northern Minnesota and come to where we can tell them a thing or two about harsh conditions.
     
  6. JakeP

    JakeP S P4996 / X P6028

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    Yes we had a colder spell in January, but only minus 10F. I am going to conclude then that it was the force of the rotors moving to break the pads free, when fused on with rust after a rinse the night before. I try to clean the rust off after rinsing by driving and braking, but sometimes they stay wet and the pads are locked to the rotors the next time I drive. Have to step on the accelerator to break free, as creep is not enough.
     

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