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Rear Brake Drum Replacement?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Politburo, Mar 27, 2014.

  1. Politburo

    Politburo Active Member

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    Vehicle is a 2009, ~97,000 miles.

    Failed a state inspection at a national chain for right rear brake drum thickness. They measured it at 7.915" and apparently it should be below 7.913". Left rear was measured at 7.912".

    For reference, front discs were measured at 0.820" and 0.827".

    The technician's notesheet is a crappy copy and I can't be sure about this part, but I believe front pads were measured at 9 mm and rear shoes at 3 mm. If not then I have no idea what those numbers represent.

    The rear drum wear limit is apparently 1 mm. To me that says they do not expect it to wear all that much in comparison to the shoes, which have a range of 3 mm. Assuming the measurements are all accurate (and that the 9/3 are for the pads/shoes), is this something that seems mechanically feasible?

    I searched the site and could not find anyone discussing even the possibility of rear drum replacement. Everyone talks about replacing the shoes.

    Should be obvious by now that I am wondering about the likelihood that the shop is trying to take me for a ride, given that Prius are known for long brake life, the lack of major wear on the fronts, and lack of drum replacement discussion on the site. There are several online reviews where other people were told they had brake problems during inspection, went to another shop, and were told it was fine. I'm already planning to taking it to the dealer later today to have them inspect it, which I should be able to have done for no charge. I don't trust them all that much either, though, so trying to get as much info as possible beforehand.

    And in lieu of making another thread.. I had the engine water pump replaced last week at the dealer. Anyone know if belt replacement would normally be part of that work?
     
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The rear brake drum inner diameter starts at 7.874" and the maximum diameter is 7.913". So, if a drum has a larger diameter than that, it needs to be replaced. The brake shoes start at 4 mm thickness and must be replaced at 1 mm thickness. It is correct that the shoes should wear faster than the drums; however if the measurements are correct then the right rear drum should be replaced. The left rear drum is near the spec limit and for a complete job, it also should be replaced.

    It is true that there isn't much mention of having to do much rear brake work on the PC forums. However who knows if someone left the parking brake on, while driving your vehicle. That will wear out the rear brakes pretty quickly.

    The serpentine belt would be replaced when the engine coolant pump is replaced, if you ask for that to be done or if the service advisor upsells you on that. I would say the belt should usually be replaced when it is removed since its cost is relatively low while the impact of a failure is high.
     
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  3. Politburo

    Politburo Active Member

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    I guess my thinking is that if the parking brake had been left on, wouldn't the wear still be mainly to the shoes? I also do the vast majority of driving with the car, probably ~99.5%. Obviously that doesn't rule it out, but there's really only a couple chances over those ~100k miles where the brake could have been left on for any significant amount of time.

    Obviously confirmation of the measurements is critical and if they're correct then it's all moot, I suppose.

    Thanks.
     
  4. Politburo

    Politburo Active Member

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    Dealer said everything within spec. Unfortunately they did not note the drum thicknesses.

    Also unfortunate is that they noticed a cracked brake light housing that the first shop did not notice, so I could not have them complete the state inspection..
     
  5. bisco

    bisco cookie crumbler

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    wow, what state are you in? that's a tough inspection!
     
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  6. Britprius

    Britprius Senior Member

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    In the UK our yearly tests are very strict. Stone chips in the screen cracked mirrors or light lenses will all fail the test. The brakes are closely inspected and tested on a rolling road. Any low figures against a chart for the car or any out of balance brakes "side to side" including the parking brake will fail.
    Any lights fitted to the car must work and comply with the regulations, seat belts must be in good condition and work, tyres must be above the legal limit on tread with no cuts or bulges, all steering and suspension joints are checked for ware, and emissions are checked (does not apply to the Prius). Any holes or leaks in the exhaust or excess noise is a failure. Many more things are covered but this gives an idea.
    The test is registered on a countrywide data base. The police can tell from the registration number of the car with there car mounted camera's "ANPR automatic number plate recognition" if your car has been tested, if you have insurance, and if the car road tax has been paid. Anyone caught without insurance the car is confiscated on the spot.

    John (Britprius)
     
  7. bisco

    bisco cookie crumbler

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    how much does the inspection cost?
     
  8. Britprius

    Britprius Senior Member

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    In dollars $100. Every car over 3 rears old has to be tested every year. If the car fails the test, when the work has been put right there is a retest fee depending on the number of items it failed on. The car cannot be used on the road apart from being delivered for repairs or testing until the car passes the test.

    John (Britprius)
     
  9. bisco

    bisco cookie crumbler

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    ours is $29., i guess you get what you pay for.;)
     
  10. Britprius

    Britprius Senior Member

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    As Grumpy Cabby will confirm the test for taxis is much stricter still, and I do not know how much that costs. There are many different levels of test for all motorized vehicles including motor bikes and heavy goods vehicles, and the trailers for these are tested as a vehicle in there own right.

    John (Britprius)
     
  11. ursle

    ursle Gas miser

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    In New Hampshire...
    They plug in the obd2 dongle, it quierries everything, tells the state computer and for 40$ away you go.
     
  12. PriusGuy32

    PriusGuy32 Prius Driver Extraordinaire

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    I live in Michigan, suburban Detroit, the "motor city". :rolleyes:

    Ive always found it somewhat entertaining that we dont have any state vehicle inspections whatsoever. Then again, most everybody around here works for the big 3 and always have new cars (lease, demo's) anyways. You are more than welcome to receive a free inspection at most auto repair shops, but you are in no way obligated to do anything.

    I work for a safety council, and am a driver improvement instructor for the state. In all the years Ive taught driving classes, Ive never come across 1 single person in any of my classes that was involved in a crash because of, or was cited for faulty equipment. I dont know what that says, its barely scientific, just my observation.

    To the OP, I'd listen to Patrick and your inspector/mechanic. I will say that in my life, I have never replaced rear drums or shoes. Ever. Discs & rotors, yes many times. Ive never had any of the rear drum equipment wear out though.
     
  13. dogfriend

    dogfriend Human - Animal Hybrid

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    Can you get a cheap set of calipers at Harbor Freight and measure them yourself? I’ve done this on my Ford Explorer to adjust the parking brake. Sounds wrong to me that the drums would be worn out but the shoes are still ok.

    BTW, I have 90K now and the rear shoes are also about 3 mm thick.
     
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  14. Politburo

    Politburo Active Member

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    I currently have two contrary mechanic opinions.

    I went back to the first shop today and asked them to re-measure. They showed me the digital caliper reading of 7.916". Seems like it doesn't take much error in the device to affect the reading 0.04% over the measured distance but that seems like a futile argument that I don't want to get into. Might still be worth the peace of mind to measure it myself, I do not know.

    Someone else asked.. this is PA, and there's both a "safety" inspection and in certain counties also the emissions inspection which uses the OBD2. They are priced separately and each shop can set their own rate. Typically ~$50.
     
  15. fitnspark

    fitnspark Junior Member

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    what brake pads should I buy for a 2008 Pruis? The deals said I need to replace both the front and rear brakes.
     
  16. Mendel Leisk

    Mendel Leisk Senior Member

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    "deals" equals "dealer"? Assuming yes:

    The front disc brakes and rear drum brakes are completely separate systems, and the rear brake shoes tend to last a LOT longer. Is the dealership actually saying replace rear brake shoes, or just "service" the rear brakes?

    As far as what pads to get, assuming you need new ones for the front, I would just show up at the parts counter, tell them what you're driving and what you need, let them figure it out. Probably good to get a new shim set too. Use something like Sil-Glyde Brake Lubricant on the caliper pins, and a sparing amount of molybdenum anti-seize compounds on all the pads to shims to caliper contact point.

    If you're getting into DIY: don't by new pads without verfiying thickness first. Fronts are something like 10mm new, and service limit 1mm. Still, if they're only 2~3mm, maybe time anyway. Rear drum brake shoes typically start out around 4mm, service limit 1mm.

    Do disconnect the 12 volt battery negative lead before starting anything. Once everything is fully reassembled, press the brake pedal multiple times to take up any excess travel, and only then reconnect the 12 volt.
     
    #16 Mendel Leisk, Jul 17, 2017
    Last edited: Jul 17, 2017