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Rear Drum Brake Shoe Thickness

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Aaron, Nov 16, 2013.

  1. Aaron

    Aaron Member

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    Getting ready to perform the clean and adjust rear brakes maintenance. I took a digital caliper and measured my rear drum brake thickness. The thinnest measurement I got was 3.19 mm.

    I looked up the specifications and rear shoes brand-new are 4 mm. Minimum thickness allowed is 1mm.

    I have 95K on my 2008. Since my brake shoes are showing close to brand-new measurements does this mean my rear drums are out of adjustment or is this normal?

    XT1080 ?
     
    #1 Aaron, Nov 16, 2013
  2. jadziasman

    jadziasman Prius owner emeritus

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    Well not exactly close to brand new - about 20%wear.

    I'd say you have normal wear on the shoes.
     
    #2 jadziasman, Nov 16, 2013
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Normal, because the friction brakes are very gently used in normal driving, with the rear brakes even less used than the front.
     
    #3 Patrick Wong, Nov 16, 2013
  4. Aaron

    Aaron Member

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    Thanks fellas. How OCD do I need to get on "slight resistance when spinning the tires" when adjusting the star wheel? These drums are self adjusting, right?

    XT1080 ?
     
    #4 Aaron, Nov 16, 2013
  5. jadziasman

    jadziasman Prius owner emeritus

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    According to the service manual, you should adjust the brake shoe clearance with the wheel installed using only 2 lug nuts. It says to remove the access hole plug from the backing plate and to turn the adjuster to expand the shoe until the drum locks. Then rotate the adjuster by 8 notches to obtain the proper clearance. Don't forget to reinstall the plug into the backing plate.
     
    #5 jadziasman, Nov 16, 2013
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  6. Aaron

    Aaron Member

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    Interesting. I know the service manual is never wrong, but if you adjust it all the way until the drum locks how do you then rotate the star wheel 8 clicks in the opposite direction when it's only meant to rotate the one way? In order to rotate to make the adjustment loose you would have to take the drum cover off and lift up the adjustment arm and spin the star wheel in the opposite direction. Something you can't do from the access hole in the back.

    Xoom ?
     
    #6 Aaron, Nov 16, 2013
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes, the rear drums are self-adjusting when you back up and apply the brakes.

    If necessary, use one screwdriver to move the adjustment arm out of the way while you use another screwdriver to make the star wheel 8 clicks loose from the drum-locked position.
     
    #7 Patrick Wong, Nov 16, 2013
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  8. jadziasman

    jadziasman Prius owner emeritus

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    Dang it, Patrick beat me to the punch again :)
     
    #8 jadziasman, Nov 16, 2013
  9. Aaron

    Aaron Member

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    Just tried this method. The only problem is you can't count the 8 clicks loose because it only clicks when tightening. You definitely have to move the adjustment arm up and out of the way in order to rotate the star wheel in the opposite direction.

    XT1080 ?
     
    #9 Aaron, Nov 16, 2013
  10. jadziasman

    jadziasman Prius owner emeritus

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    Is that what you ended up doing? The service manual indicates you need to rotate the star wheel 8 notches which it seems you're forced to determine by sight. I suppose a person would become adept at it after a few brake jobs. I'm sure that Toyota mechanics know of an easier way.
     
    #10 jadziasman, Nov 16, 2013
  11. Aaron

    Aaron Member

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    Yeah, wasn't bad. You just have to estimate what 8 clicks would be.

    XT1080 ?
     
    #11 Aaron, Nov 16, 2013
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