new 2010 III - brakes questions

Discussion in 'Newbie Forum' started by calbruc, Jul 1, 2011.

  1. calbruc

    calbruc Junior Member

    Joined:
    Jun 15, 2011
    10
    0
    0
    Location:
    New Jersey
    Vehicle:
    2010 Prius
    Model:
    III
    Hi all.

    I just got a used 2010 III about a week and a half ago and love it so far. I'm finding the brakes a little weird, though, and was hoping to get some clarification.

    First of all, there's the pedal pressure. It doesn't seem linear as the pedal depresses. The first inch or so of movement in pressing the pedal, it usually seems firm, but beyond that it seems to get more "squishy" or "spongey" the further down I push. Is this normal?

    Also, how much of braking is regenerative (engine braking)? Is it totally apparent when you are using the friction brakes? I had to slow down rapidly at highway speeds last night, and definitely noticed it felt different, but I'm not sure I've felt that same thing just driving around town and/or braking gently.

    Thanks for your input!
     
  2. Gurple42

    Gurple42 New Member

    Joined:
    Mar 10, 2011
    354
    41
    3
    Location:
    Santa Monica, Ca.
    Vehicle:
    2011 Prius
    Model:
    Two
    From what I've read on this forum, the majority of your braking is regenerative. That's why the brakes last 100k+. I seem to remember reading that the last5-7mph you are using friction brakes under normal or gentle pressure. Under hard breaking, it's got to be mostly regular brakes and yes the pedal feels different under varied pressures, it is normal.:)
     
  3. olyprius

    olyprius Member

    Joined:
    Jan 1, 2011
    194
    31
    0
    Location:
    California
    Vehicle:
    2011 Prius
    Model:
    Three
    It would be nice if one of our cool geeky members on PC could hack/tap into the ECU and build a DIY LED indicator giving you real time feedback indicating if you are in regen vs regular braking. Like, green if in regen, and red if using regular breaking.

    For now, but not as precise, I just monitor the HSI and make sure the CHG bar (that indicates regen) is not a FULL bar, but rather a partial bar.
     
  4. calbruc

    calbruc Junior Member

    Joined:
    Jun 15, 2011
    10
    0
    0
    Location:
    New Jersey
    Vehicle:
    2010 Prius
    Model:
    III
    Okay, good to know. Thanks!

    That *would* be cool! And thanks, I'll keep an eye on that bar now.
     
  5. xpcman

    xpcman Senior Member

    Joined:
    Jun 11, 2009
    1,302
    292
    0
    Location:
    California - SF Bay area
    Vehicle:
    2008 Prius
    Keep both eyes on the road!
     
  6. spiderman

    spiderman wretched

    Joined:
    Jul 5, 2009
    7,543
    1,542
    0
    Location:
    Alaska
    Vehicle:
    2010 Prius
    Model:
    II
    Get a ScanGuage... it tells you whether there is a charge or discharge.
     
  7. richard schumacher

    richard schumacher shortbus driver

    Joined:
    Mar 27, 2004
    7,656
    1,017
    0
    Location:
    United States
    Vehicle:
    2004 Prius
    Model:
    N/A
    Getting more squishy as it is depressed doesn't sound right. I'd have a dealer check it.
     
  8. twittel

    twittel Senior Member

    Joined:
    Jul 7, 2010
    1,605
    148
    0
    Location:
    Mt. Pleasant, SC
    Vehicle:
    2010 Prius
    Model:
    III
    The dealer should verify if the brake recall was performed.
     
  9. qbee42

    qbee42 My other car is a boat

    Joined:
    Mar 2, 2006
    18,058
    3,054
    7
    Location:
    Northern Michigan
    Vehicle:
    2006 Prius
    In normal operation (not failure fall-back mode), all brake "feel" is produced by a piston and spring. Prius braking is done "by wire", meaning the brake pedal is not mechanically operating the brakes. The hydraulic fluid from the master cylinder doesn't have anywhere to go, so Toyota engineered a "stroke simulator", which is just a piston and spring. You press the brake, the brake moves the hydraulic fluid, and the hydraulic fluid moves the stroke simulator. That's why it feels weird: you aren't really feeling the brakes.

    In the even of a system failure, special valves fail over to connect the hydraulics directly to the brakes, reverting to normal mechanical brake operation.

    As for the question of how much braking is regenerative, the answer is all of it, up to the limits of the battery to absorb electricity. Gentle braking will almost always be totally regenerative.

    There are three exceptions to this general rule: low speed, panic braking, and ABS. At very low speeds (under 10 mph, roughly) there isn't enough electrical generation to effectively regenerate, so the Prius switches to friction braking. This is the funny feeling you get at around four mph.

    During a panic stop you don't have time to mess around with regeneration, so the system goes directly to assisted friction braking.

    Likewise when you lose traction during braking. Regenerative braking works with only the front wheels, so at the first loss of traction the braking system switches to ABS friction brakes. The loss of traction and ABS action produces the much maligned "brake dropout" or "shooting ahead" that people complain about in numerous posts. If you feel this during braking, keep pressing - you *will* stop.

    Tom
     
  10. twittel

    twittel Senior Member

    Joined:
    Jul 7, 2010
    1,605
    148
    0
    Location:
    Mt. Pleasant, SC
    Vehicle:
    2010 Prius
    Model:
    III
    Tom, does your Michigan winters cause your Prius ABS to activate much? If so, how is the stability,handling and straight line lane control? Here in Carolina I've not yet had a chance to see ABS in action, though we get some ice and snow once in a while.
     
  11. qbee42

    qbee42 My other car is a boat

    Joined:
    Mar 2, 2006
    18,058
    3,054
    7
    Location:
    Northern Michigan
    Vehicle:
    2006 Prius
    I have a Gen II, so take my answers with the appropriate grain of salt. My model has VSC.

    Short answer to your question: yes. I probably should say YES, with all caps, since we slide around all winter.

    My 2006 Prius with VSC is the best handling winter car that I have ever owned, and that includes a Jeep C-J5, a four wheel drive Subaru, and a Ford Aerostar with electronic four wheel drive. The Prius can't wade through deep snow, and traction control can be a problem, but when it comes to handling it beats them all, hands down.

    I have to remind myself that the roads are slippery. The Prius does such a good job evening out braking and compensating that you don't really feel the conditions.

    Obviously you need good tires. The OEM Goodyear Integrity tires were a disaster. I gave those away the first winter and bought some real tires.

    Tom
     
    1 person likes this.
Loading...