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Wobbly braking?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Erik Aalto, Jan 5, 2012.

  1. Erik Aalto

    Erik Aalto Junior Member

    Joined:
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    Location:
    North Carolina
    Vehicle:
    2011 Prius
    Model:
    Two
    I'm not quite sure how best to describe this, but a good portion of the time, as I am coming to a stop it feels as if my front brakes (feels like it is coming from front right of the car) are "wobbly." There is a noticeable unevenness in braking force, it gets stronger than weaker, and as the car comes to a stop (this is with friction brakes applied), the car almost feels like it is hobbling. It's feel is similar to having misaligned brakes on a bicycle wheel.

    I have no issues at any other point whilst driving (besides ratcheting clank, also suspected from front right). I still get 50+ MPG, and front pads were at 6 MM as of last service, due in 700 miles for next service. Car is a 2008, currently at 113,000 miles. EDIT: Forgot to include - new tires @ 95K, 4 wheel alignment @ 95K.

    Online searches have said there could be a number of culprits: warped rotor, loose rotor, bad bearing, CV joint.

    I'm going to ask the dealer to take a look at it when I go in for service in a few weeks, but was curious if anyone here has experienced this problem, and if it is something that is a DIY job, or can lend some insight into the cost of such a job.
     
    #1 Erik Aalto, Jan 5, 2012
  2. fuzzy1

    fuzzy1 Senior Member

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    This sounds similar to the warped rotors I suffered a couple times in a previous car. Several coworkers suffered the same issue on the same model, so it seemed to be a pattern, but I am not aware of any such pattern on the Prius. Potential causes included overheating -- not likely in a Prius or my old car -- and uneven or over-torquing of the lug nuts when changing tires.

    The solution was to turn them on a lathe, shaving off the high spots, and of course shortening their service life. Don't remember the cost, but it is something many shops insist of doing whenever changing brake pads, whether needed or not. To prevent repeats, I bought a torque wrench and have been carefully applying it ever since.

    I don't know enough about the other potential causes you listed to comment about them.
     
    #2 fuzzy1, Jan 5, 2012
  3. jpadc

    jpadc Type before I think too often

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    Sounds like warped rotors alright. I'm sure you noticed in your search how rare rotor replacement is on a Prius (unless they rust out) Getting warped is uncommon. Either you are just really hard on them or perhaps a bad bearing... but if it was generating that kind of heat, you would likely hear them and see the effects on your MPGs.

    Let us know what the dealer thinks about the likely cause...
     
    #3 jpadc, Jan 5, 2012
  4. qbee42

    qbee42 My other car is a boat

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    Vehicle:
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    As suggested, it's most likely warped rotors. But just in case, have you tried cleaning your rotors? Prius brakes don't get much use, and it is common for them to get rusty and dirty.

    The easiest way to clean the rotors is to force friction braking. You can do this by getting up to 40 or so on an empty road, shift to N, and press the brakes to slow down. Repeat a few times as necessary. Shifting to N keeps regenerative braking from running, so your Prius is forced to use the friction brakes.

    Tom
     
    #4 qbee42, Jan 5, 2012
  5. Erik Aalto

    Erik Aalto Junior Member

    Joined:
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    Location:
    North Carolina
    Vehicle:
    2011 Prius
    Model:
    Two
    It really has struck me as odd, and I definitely will try to clean the rotors as you have suggested.

    An interesting point came up in conversation: I was having a hard time figuring out why this would be an issue with my brakes because I honestly don't use them that often. When I see a red light I coast up to it, and usually don't have to brake until I am below 15 MPH. I coast to stop signs. I coast, coast coast. The question was posed to me. How does your wife drive? This car was primarily driven by my wife for a probably 90,000 of it's current 113,000 miles, as will be the case with the 2011 we just bought. I am nearly certain that she brakes in a different manner than I do. Additionally, our 2008 lived through a few years of Los Angeles rush hour traffic, which could explain a little more wear and tear on the brakes than our 2011 will have, just because of the nature of our commutes in North Carolina (long stretches of open road with few stops).

    I guess I will find out what the issue is when I take it in for service, and if the price isn't too bad I'll go ahead with service. If the rotors are in fact warped, it was also recommended to me that I go ahead and change the pads as well, as they may have worn in the pattern of the warped brakes. They are the original brakes so it wouldn't be a big deal to replace them now, as stated before they were at 6 MM as of my last service in October, 2011.
     
    #5 Erik Aalto, Jan 6, 2012
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