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Two brakes per rear rotor

Discussion in 'Model S' started by smorgasbord, Jan 20, 2012.

  1. smorgasbord

    smorgasbord Active Member

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    I just stopped by the Santana Row store for a quick visit. I noticed the black Model S there has two disc brakes per rotor.

    I think the Roadster's brakes aren't quite up to the task of spirited driving. With a weight of 4000lbs, Model S needs good brakes, but I wonder why they didn't beef up the fronts instead?
     
  2. brianman

    brianman Burrito Founder

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    Related...

    What time is it? NAIAS TIME! | Forums | Tesla Motors
     
  3. TEG

    TEG TMC Moderator

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    Yes, I heard the same thing. Most cars I know have a cable that can actuate the main calipers for "emergency brake", but for some reason the S has a small slave caliper for that.
     
  4. Albern

    Albern Member

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    I can't recall other cars except the McLaren F1 that actually have a second set of calipers.

    I wonder if by making the parking brake electronically actuated we'll loose the function of emergency braking. What's the alternative if the braking system suddenly shuts down?
     
  5. Doug_G

    Doug_G Lead Moderator

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    Yeah, I'm Douglas3 on the Tesla forums. The main calipers are hydraulic, and the second, smaller brake shoe is actuated by a fairly beefy looking electric actuator.

    It seems very unlikely that you would lose both the hydraulic systems and the electronic systems simultaneously.
     
  6. TEG

    TEG TMC Moderator

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  7. goyogi

    goyogi Member

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    Is that a brake dust shield that's stamped with the letter T?
     
  8. TEG

    TEG TMC Moderator

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    The letters T|E|S|L|A go around that plate as I recall (not just a T).
    I think they call it a spash guard to keep road debris from striking the brake rotor. So not so much to keep brake dust in, but rather to keep contaminants out.
     
  9. WarpedOne

    WarpedOne Supreme Premier

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    All these components are bought from part suppliers. Maybe all existing brake calipers with built in "parking brake feature" aren't strong enough for S? ICE cars have bigger brakes in front, S is an exception for having really big brakes in the rear.
     
  10. GSP

    GSP Member

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    It is common for cars with 4-wheel disc brakes to use small cable actuated drum brakes in the rear for the parking brake, instead of using the main calipers.

    Also, it it interesting that the Model S uses fixed calipers, instead of the cheaper, and much more common, floating calipers. This is going to be a GREAT driver's car.

    GSP
     
  11. TEG

    TEG TMC Moderator

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  12. TEG

    TEG TMC Moderator

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    #12 TEG, Jan 21, 2012
    Last edited: Jan 21, 2012
    Apparently (retrofit?) on some Honda/Acura NSX as well.
    IMG_1319.JPG
    [​IMG]
    [​IMG]
     
  13. TEG

    TEG TMC Moderator

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    Dodge Viper:
    [​IMG]
     
  14. Cal1

    Cal1 Member

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    Are the pistons on both the main caliper and the e-brake solenoid driven? No hydraulic fluid? If there is one where is the master? If we lose power on a hill will the e-brake disengage, letting it just roll?

    Cal
     
  15. Doug_G

    Doug_G Lead Moderator

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    The e-brake is electrically driven, but is NOT a solenoid. That would not make any sense at all, as it would (a) be unsafe and (b) would consume too much power.

    It sounds like an electric motor when it engages/disengages, so I'm pretty sure that's exactly what it is. You do not have to worry about your car rolling away.
     
  16. Newscutter

    Newscutter Member

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    So in the event of a catastrophic brake fluid leak--- could the parking brake be used at the emergency brake and stop the car? In a regular car there'd also be downshift options but even with regen that might not be fast enough (like downhill).
     
  17. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Yes. Press and hold the Park button and the parking brake will engage.
     
  18. Cal1

    Cal1 Member

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    So how is it exactly engaged? Gotta be something actually pushing the pistons to pinch the rotors. Unlike the actual brake calipers I don't see any brake bleeder valves.
     
  19. Doug_G

    Doug_G Lead Moderator

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    I would imagine it's some kind of screw or cam driven by a motor and gearbox.
     
  20. tezco

    tezco Sig P85

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    On the Leaf you can pull once to activate emergency brake and pull a second time if you need more stopping action.
     

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