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Rusty Rotors

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by unit333, Jul 22, 2013.

  1. unit333

    unit333 Junior Member

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    Hi

    So I took my Prius (23,000 miles) to get oil change and tire rotation. Not at the dealer but at a small relatively reputable shop that I use on and off.
    They said my brakes are still fine but I should probably consider replacing the rotors as they are real rusty. Since I am not a car expert I ask them what would happen if I don't change them, according to the guy it should be fine for now but if i start feeling my brakes not catching 100% then I should definitely replace them. $600 bucks quote.
    I read on the forum various opinions, including someone who said that this is a common way for mechanic to make some extra money from Prius owners, as the rots do rust quite often.
    In your expert opinions what should I do and how serious or not this issue is in a long run?

    Thanks!
     
  2. TwoUnderPar

    TwoUnderPar Member

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    Rusty rotors are not an issue... at all.... none... zero.
     
  3. Bill Norton

    Bill Norton Senior Member

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    Do a SAFE panic stop from >70MPH.

    It's good practice for you and you will now have clean shiny rotors!

    Look at them before and after,, if you can see anything through the plastic wheel covers.
    Did you actually SEE the reported rust?
     
  4. unit333

    unit333 Junior Member

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    Yeah I can definitely see rust. I've noticed it a while ago too but never really looked at it as a problem. So if I do a sudden stop from a fast speed the disk brakes will maybe clean some of that out?
     
  5. jdenenberg

    jdenenberg EE Professor

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    It is better to get a Prius up to 25-30 MPH, put it in neutral to disable regeneration and lightly apply your brakes to clean off the rotor surfaces. Repeat as necessary.

    JeffD
     
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  6. Bill Norton

    Bill Norton Senior Member

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    That will clean ALL the rust off.

    Don't be shy about it. You have to be alone with no one following you, right?
    This is good practice for you for when one of our aging bridges collapse in front of you,, or some such scenario!!!

    Look at the discs with a flashlight before and after.
    You may smell hot brakes because typical Prius brakes have an extra easy life and never get warmed up all the way.
    Think of it as a safety test for the car. You want it to be able perform a panic stop, right?

    Let us know how they look!!
     
  7. JMD

    JMD 2012 Prius 4 Solar Roof

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    Just ride the brake a little and the pads will clean it up.
     
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  8. 32kcolors

    32kcolors Senior Member

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    I see it from time to time and it's the result of the Prius using regenerative braking the vast majority of the time, but there's no real need to clear it off. The shop obviously doesn't know anything about the Prius braking system. You need not do anything.
     
  9. Bill Norton

    Bill Norton Senior Member

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    Regardless of the car; you need clean smooth rotors, not textured rusty rotors, for if/when you need max performance from your brakes.

    A practice panic stop will let you experience one before you NEED ONE.
     
  10. 32kcolors

    32kcolors Senior Member

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    I think this is overkill in terms of real world situation. The vast majority of Prius owners (especially outside of PC) who don't know any better haven't gotten into any major accident as a result of temporary rust on the rotors and Toyota would've implemented some kind of system to enable friction braking to clear off the rust if it were a major problem.
     
  11. MJFrog

    MJFrog Active Member

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    I would disagree to a certain extent with this. A little bit of rust...ok, but if it goes on long enough the rotors will wind up being pitted. This is something a bit more serious than some temporary rust.
     
  12. jdenenberg

    jdenenberg EE Professor

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    There is already a technique to disable regeneration and enable friction braking; It's called neutral. See my reply to Bill a few messages above.

    JeffD
     
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  13. unit333

    unit333 Junior Member

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    Thanks, I'll test the suggestions and let you know
     
  14. 32kcolors

    32kcolors Senior Member

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    How do you know that the OP's problem is a bit more serious than some temporary rust. All we have is the shop's words and it could be a lie. My rotors can look pretty bad just a few hours after a car wash but they eventually clear.

    What I meant is if temporary rust is such a problem as to become a safety issue in case of a panic stop, Toyota would have implemented a system to clear the rust on its own. Not talking about a technique that we can do voluntarily.
     
  15. css28

    css28 Senior Member

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    Basic truth: If you see persistent rust on the visible surface of the rotor, there is much more rust on the inboard side of the rotor.

    Rotors can rust to the point that more than half of the effective braking area is persistent rust that won't clean off from a few hard applications of the brakes. This happens much more on vehicles that sleep outdoors. Non-hybrid vehicles.

    It's irresponsible to suggest that rusty rotors are a myth.
     
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  16. 32kcolors

    32kcolors Senior Member

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    I don't disagree with any of the above; however, rusty rotors are a different breed on the Prius because it uses regenerative braking a majority of the time. The OP needs to discriminate between the two and I'd suggest getting a second opinion from someone who's actually familiar with the Prius.
     
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  17. Bill Norton

    Bill Norton Senior Member

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    Brakes is Brakes.
     
  18. TwoUnderPar

    TwoUnderPar Member

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    It's irresponsible to suggest that rusty rotors are a problem. Sure... if they get pitted, then during one of those panic stops it might cause your brake pads to wear a little more pad material off than they would otherwise, but they are absolutely no problem. Rotors don't have to be smooth. They have to be flat (not warped) but not smooth. Bill is absolutely correct. Brakes is brakes.
     

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  19. jdenenberg

    jdenenberg EE Professor

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    OK, enough arguing. Rust on the rotor surfaces will cause some braking noise, somewhat faster pad wear, and harsher transitions between regenerative and friction braking. I regularly clean my 2004 Prius rotor surfaces using neutral and my brakes are still original at 243k miles.

    There is also rust that forms on the outer edges of the rotors. This is unsightly but usually does not affect functionality. It will cause the brakes to heat up faster (due to reduced air flow) when using the friction brakes excessively (like when going down a mountain when the HV battery gets full - no regeneration due to nowhere to put the energy.). There are replacement rotors that have a rust resistant plating that would minimize edge rust (If I ever have to do a brake job), but the surface quickly wears off so that surface rust should still be managed.

    JeffD
     
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  20. 32kcolors

    32kcolors Senior Member

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    I don't know about the Gen II, but on the Gen III we can shift into B to enable engine braking.