Do i need new rotors?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by coppercumin20, Oct 15, 2021.

  1. coppercumin20

    coppercumin20 New Member

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    So my 2006 finally passed state inspection. When i dropped it off i also brought the new front pads i bought, and asked the mechanic to also swap the pads out. He called me back and said he wouldn't do it without also changing the rotors (actually, he normally doesn't use pads someone already bought - i think he only agreed because he felt bad for me because i missed the reinspection window by 2 days and had to pay for a full reinspection).

    Looking at the inspection specs, i still have some good metal left on the rotors - i don't have the exact value, but it was over 0.8", and the spec was something like 0.76". I'm not sure, however, whether they are too grooved.

    How much grooving is okay? If i find someone else to slap on the new brakes, am i just wasting the money i spent getting OEM? I know people think highly of OEM parts here, but are OEM rotors *that* much better that i should slap new brakes on old rotors rather than get new aftermarket?

    These are the best photos i could get. To the touch, my front rotors do not feel perfectly smooth, but i didn't think it was an issue until the mechanic brought it up.
     

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    #1 coppercumin20, Oct 15, 2021
    Last edited: Oct 15, 2021
  2. nancytheprius

    nancytheprius Member

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    How many miles on the car and how much longer do you plan on driving it for?
     
  3. JC91006

    JC91006 Senior Member

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    No professional is going to put their business name at risk in doing a brake job that isn't safe. Brakes are used to stop that hunk of metal you're driving and if anything goes wrong, it's the guy that touched it last that gets the blame.
     
  4. Mendel Leisk

    Mendel Leisk Sand Pounder

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    2nd gen rotor specs and inspection procedure are in the attached. How many miles on those rotors, and they're original? They look good.
     

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  5. coppercumin20

    coppercumin20 New Member

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    The car has 136,000 miles. I'm not *sure* if original rotors (I bought the car just over 1 month ago), but going off the Carfax, yes.
     
  6. sam spade 2

    sam spade 2 Senior Member

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    NO rotor with more than 100 miles on it will be perfectly smooth.
    Getting close to minimum thickness OR obvious deep gouges OR out-of-true causing pedal vibration......are all immediate FAILS.

    If you hope to keep it for a while, probably a good thing to do now.
     
  7. sam spade 2

    sam spade 2 Senior Member

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    But a really LOT of them will put their business at risk by lying to people, it seems.
    And eventually the word gets around.
     
  8. pasadena_commut

    pasadena_commut Active Member

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    The goal is to be sure that both the rotors and the pads are within spec at all times. If the rotors are on the hairy edge of "acceptable" now they could be well past "acceptable" before the pads wear down again. Rotors are not very expensive, and if the pads need to be changed anyway, might as well play it safe and replace both.
     
  9. coppercumin20

    coppercumin20 New Member

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    No pedal vibrations. They do squeak sometimes, but a lot less now that the mechanic lubricated the calipers, and still with the unevenly worn pads.

    Found the actual measurements. Left has .856, right has .852, and the minimum thickness is .787, so they're well within spec. According to what Mendel sent me, they've only got about 0.4 mm of wear.

    So the issue is that in terms of thickness, it's FINE. And as you say, no rotor this old is perfectly smooth. I can't see any deep gouges on the outward faces, and going by touch, (outsides and what i can feel in the insides) they feel pretty smooth, although not perfectly so.
     
    #9 coppercumin20, Oct 16, 2021
    Last edited: Oct 16, 2021
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  10. coppercumin20

    coppercumin20 New Member

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    Said elsewhere, but ~137k. I plan to drive it until the battery dies, and decide from there whether to swap the battery or get a new car, based on whether it's showing warning signs of like, the actuator going out or something.
     
  11. Mendel Leisk

    Mendel Leisk Sand Pounder

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    There's also a runout check, which requires a dial indicator, typically attached to an arm with magnetic base. That said, if you're not feeling any pulsing, it's likely all good. FWIW, I've only ONCE needed a rotor replaced (decades back), ran down past min thickness, and developed a crack.
     
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  12. coppercumin20

    coppercumin20 New Member

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    Yeah, I'm thinking i just need to find somewhere that'll turn them - I'm pretty sure the mechanic only wanted to sell me new ones because they don't *do* turning (and so he'd make money).
     
  13. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Wouldn't bother, and it just reduces their thickness.
     
  14. sam spade 2

    sam spade 2 Senior Member

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    NOT a practical option.
    Modern car makers almost ALL put on MUCH thinner rotors these days and there really isn't enough material there to "turn" without cutting it below the minimum spec.
    When they get down close to the minimum spec. OR show signs of serious damage, they really NEED to be replaced.
     
  15. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Bottom line: the rotors look good, have lots of thickness, aren't pulsing; what's not to like.
     
  16. ChapmanF

    ChapmanF Senior Member

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    A Gen 2 front rotor is born with 22 mm thickness and goes to pasture at 20 mm.

    If you make a 0.15 mm cut on each side, that's 0.3 mm off the rotor. If you do two such passes, 0.6 mm off.

    A machine shop might decline to turn it if there's less than about 0.8 mm remaining, so at least it could have a couple machining passes and still some margin remaining for wear. Given a Prius rotor is born with 2 mm to go, machining can be practical as long as it is not too worn or too grooved by the time the job is considered.
     
  17. coppercumin20

    coppercumin20 New Member

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    I was told you have to either turn or replace rotors when you get pads.
     
  18. sam spade 2

    sam spade 2 Senior Member

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    You were told......WRONG. Absolutely, totally wrong.

    You should stop listening to that person, whoever it is.
    Probably someone who will profit from selling you stuff you don't really need.
     
  19. Mendel Leisk

    Mendel Leisk Sand Pounder

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    I would only change them if they're deeply scored, seriously rust-pitted, cracked*, near-or-below minimum thickness, or way out-of-true, the last two per the Toyota specs.

    * Had that happen to me, once.
     
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