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PD-M646 Overhaul Walkthrough

Discussion in 'The Shop' started by erikkellison, Oct 8, 2006.

  1. erikkellison

    erikkellison Monkey

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    Okay, so I hear these pedals are no longer made, and are great. I for one am quite impressed with the quality. So, knowing I was going to overhaul a set of them prior to sale (since I don't ride clipless), I decided to make it a photo-walkthrough. There are a couple hangups that a walkthrough might help with.
    So, to start, you need the following:
    • Vice grips OR Shimano pedal spline tool
    • Phillips screwdriver
    • 10mm end wrench
    • 7mm end wrench
    • 6mm allen
    • 3mm allen
    • good grease

    First step is to take out the spindle by using vice grips or the Shimano tool if you have one. Take note that the left pedal is standard thread, the right pedal is reverse thread. It will require many turns to remove, and may be quite difficult at first. Be sure to have the vice grips tight enough so they don't slip, but not too tight that you're actually squishing the "nut" as it is hollow inside, and prone to damage.

    Second stem is to remove the sleeve that fits inside the cage and part of the pedal itself, which links the two and provides a catch to prevent overrotation of the pedal.

    Now comes the tricky part that a walkthrough is really handy for. Most Shimano pedals have an endcap that simply pries off with a small screwdriver. Not this one. You have to stick a phillips screwdriver down the center of the pedal and unscrew a tiny screw that is holding the endcap on, keeping the tension spring in place.

    Now you can remove the endcap, the washer (of sorts) that fits inside, and the tension spring that prevents overrotation. Once all that is removed, the pedal itself will fall free of the cage.


    Now is the time to clean everything. Make sure you get all the dirt and nastiness out, and regrease everything copiously.
    Note here that with Shimano pedals, I have found a certain step unnecessary even with 2 year or more old pedals. The grease in the bearings and bushing on the inside is usually clean, and does not need replacement. I merely clean off all the old grease, loosen the preload on the bearings, and squeeze some new grease in there. Then I reset the preload by screwing in the inner nut a little too tight, screwing the outer not snug onto it, and then backing off the inner nut until I achieve the appropriate bearing action.

    Now I take off the inner side of the pedal because I will need the room to adjust the preload on the spring.
    After that's done, I proceed to put the endcap washer onto the endcap, and the tension spring onto that, all copiously flowing with grease. I slide it into position, and then put the pedal into position by making sure the end of the tension spring goes into the small hole in the pedal. Making sure it's all seated, I insert and screw the small screw that goes inside the spindle. After I have it screwed in, I back it off a few turns so as to develop some play. While keeping the pedal aligned, I rotate the pedal so as to achieve some spring preload. It will need to have enough play to barely slip over the stop that is a part of the cage. Once preloaded and past the stop, I retighten the screw.

    I now reattach the rest of the cage. Then I slide the bushing in place, taking note that the side with the teeth points toward the pedal, and not the imaginary crankarm (this limits overrotation as well).

    I then screw the spindle (with grease everywhere, of course) back into the assembly, and snug it up. The spindle should spin well, feel like a new bearing, and the pedal should rotate, but be under good tension, and have no play.

    I hope this helps one other person, Shimano pedals, if you aren't familiar with them, can be tricky to overhaul.
     
    #1 -   Oct 8, 2006

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  2. nycurse

    nycurse Monkey

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    sticky it! great walk through bud. my friend has some and he has no problem with them
     
    #2 -   Oct 8, 2006
  3. mshred

    mshred Monkey

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    i agree!

    :cheers:
     
    #3 -   Oct 8, 2006
  4. nycurse

    nycurse Monkey

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    im might be making even more of there tutorials for people.
     
    #4 -   Oct 8, 2006
  5. binary visions

    binary visions The voice of reason

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    Great thread. Stuck!
     
    #5 -   Oct 8, 2006
  6. elf 232

    elf 232 fewchur serjin

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    ouch, your fingernail looks pretty mangled.


    helpful thread thanx!
     
    #6 -   Feb 7, 2007
  7. Gossioii6

    Gossioii6 Chimp

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    Good post! I plan to move into this stuff after I’m done with school, as most of it is time consuming. It’s a great post to reference back to. My blog needs more time to gain in popularity anyway.
     
  8. stringcheese

    stringcheese Monkey

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    Seriously what happened to your thumb nail?


    PS my pedals are going to appreciate your guide/reminder

    edit: nevermind, old thread
     
    #8 -   Apr 17, 2009
    Last edited: Apr 17, 2009
  9. erikkellison

    erikkellison Monkey

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    Hammer
    PS
    Reported the spammer.
     
  10. jonKranked

    jonKranked Press Button, Receive Stupid

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    Hey Erik I've got a pair of the shimano 747's... they looked almost identical to the 646's except they were red. Would the rebuild be the same? Or are there some differences?
     
  11. erikkellison

    erikkellison Monkey

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    Jon,
    Honestly, I don't know - I never rebuilt the 747's. My guess is that they're identical with some material differences, but I guess you'll be the one to find out :)
     
  12. jonKranked

    jonKranked Press Button, Receive Stupid

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    bump.... what's the axle bearing size?
     
  13. Polandspring88

    Polandspring88 Superman

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    There is no axle bearing, at least there wasn't in my 647s, which look to have the same guts. There were only the two sets of cup n' cones with trapped ball bearings. In that case they are 3/32" ball bearings. I don't know if that addressed what you were asking but...
     
  14. jonKranked

    jonKranked Press Button, Receive Stupid

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    yea it's the loose bearings. shoulda clarified. thanks for the info! off to mcmaster.com....
     
  15. Polandspring88

    Polandspring88 Superman

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    Best of luck rebuilding them, I pulled the retaining nut off the axle and heard a tinkling noise as ball bearings hit the floor and began rolling in all directions. Almost threw the pedal through a window trying to get them all to stay in place while I reassembled everything.
     
  16. jonKranked

    jonKranked Press Button, Receive Stupid

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    I've rebuilt them before. Yea, it can be tricky, but its definitely do-able, just gotta be patient.
     
  17. Jm_

    Jm_ Turbo Monkey

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    This is cool. I made a tutorial for the same thing with 545 pedals a few years back:

    The only problem I've ever had with these pedals is that after a while the cage gets loose because the pedal/cage interface wears out. There's a small screw that threads into the end-cap assembly, this loosens and eventually the threads get all screwed up, then the cage gets really loose. I have 2 complete sets of 545s, one is over 4 years old. Unfortunately, way back in the day I had another set and I threw them away after this aspect appeared to have failed, but if I didn't I could have 3 functional sets.

    Anyways, here are the parts. New parts on the bottom left: cap, plastic bushing, screw, spring. I don't recall what the part # is right now for the end-cap assembly, but it is shown on the pedal-diagram on Shimano's website, so it's relatively easy to find.






    I suggest lock-tighting the screw, it is what eventually came loose in the fist place.



    Dissasemble the pedal first. This isn't too difficult. Grasp the pedal cage (shown in later step) and use an adjustable wrench on the flats provided on the spindle (not the flats used to install/remove the pedal) to take the spindle out of the pedal mechanism. You might have to stick a phillips screwdriver into the mechanism to loosen the screw (the screw that is to be replaced), but if you're doing this repair for the same reason as I, it will probably fall apart when you do the first step. Next, line up spring in the hole, then get the spring into the detent on the left side (I used a flat-head screwdriver to coerce the spring into the slot.







    Then use a phillips screwdriver, the screw that came with the kit, and insert it into the pedal mechanism, you have to kind of hold the entire thing together untill you get it in there a bit. Grasp the pedal body with your other hand to brace againt something to tighten it. Get it nice and tight (also what the locktite is for).



    Then screw the spindle back into the mechanism and cage. Hold the pedal body with one hand and use an adjustable flat wrench in the other hand to tighten it into the body.

     
    #17 -   May 26, 2013
    Last edited: May 26, 2013
  18. Katalogi

    Katalogi Chimp

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    Good thread, I have a problem with my pedals and I was looking for information how to do it. And I will go with your instruction :)
     
  19. Full Trucker

    Full Trucker Frikkin newb!!!

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    I have piles of m636 pedals, they're pretty much all I use. Gonna get in to a pair and see how similar the overhaul process is. I would guess fairly similar, except the m636 doesn't have the outer end cap thingy.
     
  20. johnbryanpeters

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    I could never get 636 bearings adjusted to my satisfaction when trying to rebuild. I still have a small pile of them, but the only bike equipped with them is my road bike.