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Hydraulic Brakes feel weak.

Discussion in 'Model S: Driving Dynamics' started by randvegeta, Jan 29, 2017.

  1. randvegeta

    randvegeta Member

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    Ive been driving my 2014 Model S 60 for a little over a month now and haven't really noticed this until recently.

    I don't drive particularly aggressively and the regenerative brakes have been more than adequate for 99% of my daily needs, only using the traditional brakes to completely stop.

    However, I have driven a few times on a cold soaked, or fully charged battery where the regen is completely disabled, and on these occasions, and it feels the hydraulic brakes are far too weak for the weight of the car when travelling at speed.

    I feel I need to really press down on the brake pedal to get any significant braking power. Without the regen, it sometimes feels like there is no braking power at all when travelling above 100km/h, or if needing to slow very quickly.

    Does anyone else fine the brakes a little under-powered? Or could this be a problem with my vacuum pump? Any one have any ideas?
     
  2. jaguar36

    jaguar36 Active Member

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    When working properly the brakes on the the Model S are quite good. Stopping distances being on par with a BMW 535i or A6.

    My first guess would be that you just aren't used to how they feel. The other issue may be rust on the brakes, which is a common occurrence on all cars when the brakes get wet, however is far more noticeable on a Tesla since you typically don't use the brakes much.

    Its also possible of course that you've got a problem with the brakes, so it would be prudent to get them checked out.
     
  3. randvegeta

    randvegeta Member

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    There is little/no rust. I've driven big Audis and Mercedes before and the responsiveness and braking power certainly seems much worse than other big cars. Luckily I don't drive like a maniac.

    The brakes DOO work so I assume if there is a problem, it may just be related to under-powered vacuum pump? Perhaps the pressure is low?
     
  4. randvegeta

    randvegeta Member

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    So a little more detail after some further testing today.

    I think the problem may be related to the available pressure. Seems that when I use the brakes, it gets 'used up' somewhat and then needs some time for the vacuum pump to kick in. So I think it is during these times, when I am braking hard and just before/during the vacuum pump kicks in.

    It's certainly not always a problem as I thought it may have been. It comes and goes.. Anyone else see this?
     
  5. Ohji

    Ohji Member

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    I have noticed the brake feel on the car is VERY different than my Mercedes. I don't know how to describe it, but it feels somewhat non-linear. If I press on the brakes, there is an initial mild braking effect, and then there seems to be this sensation of... resistance. That's the best way I can describe it. I have to then push much harder to get more braking. I thought something was wrong at first, but I had an incident where I had to brake hard, and the brakes worked extremely well. I am getting more used to the difference in the pressure needed on the pedal - it is far more than I would need to achieve similar stopping power in my Mercedes.

    I read an old thread somewhere that said Tesla can adjust the feel of the brake pedal, but I have found I am getting used to it now...
     
  6. mspohr

    mspohr Active Member

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    It sounds like you are assuming you have the vacuum pump system which was installed on older cars. Newer cars have the Bosch iBooster (fully electric) system which will have a different feel.
    If you feel that your brakes aren't working well, I'd have them checked out. Brakes are important.
     
  7. animorph

    animorph Member

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    The car is old enough that the brake fluid may need to be changed. That can cause a mushy pedal.
     
    • Helpful x 1
  8. randvegeta

    randvegeta Member

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    My car is 2014. When did the new Bosch iBooster system come out? FYI, I can HEAR the vacuum pump. If what I am hearing is not a vacuum pump, then I wonder what it is.

    However, I think what @Ohji said may be what I am experiencing. I don't use the brakes a lot given the regen means I only use the brakes to come to a COMPLETE stop. I have never had any problems with the brakes at low speeds. And in the last couple of days, I have tried doing a few EMERGENCY stops, slamming on the brakes very hard while driving at a reasonable speed. It did seem to stop quite well.

    So it may be just this middle ground area where braking power is 'non linear'. Might turn off my regen, find an empty road and try and get a feel for how much pressure I need for various level of braking power.
     
  9. mspohr

    mspohr Active Member

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    I'm not sure when they switched to the iBooster but I think it was with AP 1 so late 2014. If you hear a vacuum pump, you probably have one. The iBooster doesn't have a pump. Some people have reported defective pumps so yours might be weak. It wouldn't hurt to have it checked.
     
  10. scottm

    scottm Active Member

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    #10 scottm, Jan 31, 2017
    Last edited: Jan 31, 2017
    I got the same hydraulic brakes as you, they're excellent stoppers with great brake pedal feel. Highly rated.

    I'll put money on you having some seized brake pads in the calipers.

    People don't think to service the brakes much on these cars because they hardly use any friction material. At least, I didn't pay any attention for about a year and half.

    What happens is road crud builds up in the calipers and on my car, on three corners... the inside brake pads was firmly frozen in place in the caliper. And on the 4th corner the inside pad was almost frozen - moved a bit. For me, only the outside pads at each corner were applying pressure on half the disc (no longer pinching the disc but pressing on one side of it) and needless to say my braking distances had grown to *sugar*... Pressing hard on the pedal would not STOP the car.. it just glided down in speed to a halt... probably worse than doubled the normal stopping distance of what the car should do.

    Take your wheels off, one at a time, knock out the 2 brake pad pins, slide the pads out, inspect, clean, a little lube.. re-insert... you may find some pads are stuck in place. Odds are the inside pads. Outsides will be better.

    I got all 8 of my pads moving freely again... and car stops on a dime.
     
    • Informative x 1
  11. Az_Rael

    Az_Rael Supporting Member

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    +1 Inside brake pads seized
     
  12. Ohji

    Ohji Member

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    It would be very unusual to have a seized pad on a brand new car, right? My car seems to stop okay if I push hard enough, but the pedal feels very different than any other car I've driven...
     

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