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Lesson Learned: Keep your Brake Rotors Conditioned!

Discussion in 'Roadster: Performance' started by Doug_G, May 1, 2012.

  1. Doug_G

    Doug_G Lead Moderator

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    This is to follow up on Another Tesla Crash. There was some discussion of the Roadster's brakes being inadequate.

    I've known for some time that the Roadster brake rotors get dirty/corroded because constant use of regenerative braking means they don't get enough of a workout. After the winter this year I went out and did a dozen hard stops, and braking performance improved. Less brake noise, more braking... but still less than ideal. Afterwards I could still see narrow concentric streaks of corrosion on the rotors, but they were definitely a lot cleaner.

    What really made a HUGE difference was the Autoslalom school I recently attended. We did a whole bunch of exercises, and often the braking was hard enough to trigger the ABS - I'm talking really hard braking (I was also using the sticky A048 tires). After a while I noticed the brakes were biting a lot better, and were also needing a lot less force on the pedal. The improvement wasn't just noticeable, it was significant. It wasn't just because the brakes were warmed up, because they worked just as well after lunch.

    Then I happened to look at the wheels and got a surprise. The rotors were positively gleaming - you almost needed sunglasses to look at them. What they had needed was a really good workout to clean them off properly.

    So my advice is to go out to a lonely but paved road and do several HARD STOPS - I mean emergency-level stops hard enough to trigger the ABS. Do this every day until the rotors gleam like mirrors, and then do it periodically to maintain them. The result will be night-and-day in terms of braking performance. Someday it might just save you from a crash.
     
  2. Eberhard

    Eberhard #421 Model S #S32

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    Better going on the road after a nice rainfall. Saves your rubber while getting the same result.
     
  3. doug

    doug Administrator / Head Moderator

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    Hmm... though if the ABS is activated, you're already at the traction limit, aren't you?
     
  4. Doug_G

    Doug_G Lead Moderator

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    I don't see how reducing grip with wet roads will help. You want to scrub the rotors hard. What worked for me was autoslalom on sticky tires. Exactly the opposite situation.

    ABS means you're at the traction limit, so the brakes are working as hard as possible. Threshold braking works too, but most people don't know how to do it.
     
  5. TEG

    TEG TMC Moderator

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    I think Eberhard was suggesting that perhaps rain pelting the rotors would clean them without having to brake hard.
    But, I suspect the kind of rusty corrosion buildup you are concerned about wouldn't just wash off, and needs the hard scrape of the brake pads clamping down.
     
  6. Doug_G

    Doug_G Lead Moderator

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    Right. If it was that easy to remove then using the brakes once would fix it. We're not talking about a little brake dust here. We're talking about a surface layer.
     
  7. vfx

    vfx Well-Known Member

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    I thought he meant you could brake hard in the rain and not flatspot your tires.
     
  8. Doug_G

    Doug_G Lead Moderator

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    If the ABS is oeprating you're not gonna flatspot your tires.
     
  9. doug

    doug Administrator / Head Moderator

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    My point was that if the ABS is activated, I don't see how more friction at the calipers is helpful.
     
  10. Doug_G

    Doug_G Lead Moderator

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    ABS keeps you in the vicinity of threshold braking, which means you are applying the maximum possible braking force. Maximum force means you're scrubbing the rotors (and the pads) as hard as possible.

    All I can say is that this was what seemed to be needed to really properly clean my brakes.
     
  11. doug

    doug Administrator / Head Moderator

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    I thought you were talking about being able to stop faster in an emergency.
     
  12. Doug_G

    Doug_G Lead Moderator

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    Okay, I see where you got confused - my last sentence.

    My first point was that by cleaning the brakes you'll get much better initial bite with much less pedal force. I suggested braking repeatedly hard enough to trigger ABS so the rotors got scrubbed "real good". That's why I suggested emulating an "emergency stop".

    My final point was that cleaning your brakes in this fashion could save your butt later, when you really need those brakes to bite fast!
     
  13. strider

    strider Active Member

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    Yes, this has been my experience. If I haven't used the brakes much when I do go to stomp on them initially they don't slow the car very much. But quickly the crud is rubbed off and they bite harder and even activate the ABS. I assume Doug G's point would be that in bump to bumper traffic if someone jams on their brakes in front of you you may end up traveling a decent distance before the brakes "work" and the car slows quickly. I don't think there's anything wrong w/ the brake system per se - I think the calipers have plenty of gripping power. But I have wondered if different brake pads (and/or different rotors) could help this. I would lean away from "track" or high-performance pads as they are designed to take high heat and may not work very well when cold. We should be looking at softer, more general pads that will work well even when cold. I know it might offend someone to put Camry pads on their sportscar but EVs are different. Obviously if you go and do a track day you should swap the pads for higher temp ones.
     
  14. JRP3

    JRP3 Hyperactive Member

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    I'll bring up my suggestion of aluminum rotors again. I doubt anyone makes them yet for the Roadster but a good machine shop could do a custom set if someone want's to experiment. Another possibility is stainless steel rotors, which they use on motorcycles.
     
  15. Doug_G

    Doug_G Lead Moderator

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    Metallic pads would probably do better, but they'll be noisier than the stock brakes. And of course it's a very quiet car...
     
  16. JRP3

    JRP3 Hyperactive Member

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    The issue is corrosion on the rotors, aluminum or stainless takes care of the issue. I think the softer aluminum would also provide better braking when needed, but since regen will handle the task most of the time you won't have excessive wear on the aluminum that you would with an ICE.
     
  17. TEG

    TEG TMC Moderator

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    Not practical on a very regular basis, but you can have a shop remove the rotors and resurface them periodically if you want that "like new" appearance / behavior. They use some kind of abrasive grinding wheel to clean and smooth them flat.
     
  18. Doug_G

    Doug_G Lead Moderator

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    These days shops rarely machine rotors. The rotors are cheap enough that it's better to just replace them. Also I suspect a lot of modern rotors don't have the material to spare.

    Tesla recommends replacing the rotors when you change pads. The two wear-in and adopt a complimentary profile, so if you just swap pads the contact area is limited at first, until the pads wear down - and that means the lifetime of the pads is reduced.
     
  19. JRP3

    JRP3 Hyperactive Member

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    Just had an idea for a modified compound brake pad, where a portion of the trailing end of the pad is some sort of abrasive material that dresses the rotor surface when the brakes are applied.
     
  20. smorgasbord

    smorgasbord Active Member

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    Who'd have thunk we'd be looking for something to wear down brake rotors faster? :wink:
     

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