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I have Shimano PD-T780 pedals. I bought them almost new only a year ago and they aren't cheap pedals.

Shimano PD-T780

On one pedal, the platform suddenly came off, revealing an axle which tapers off towards its end and has threads at that end barely visible through the grease in the following picture: 2 parts

The axle thing has a hex indentation on the side not visible in the picture which is used to screw it into the crank. The silver wrench ring (like a nut but no screw threads visible) attached to the platform is labelled "Tighten 10Nm" and I haven't ever turned it. I don't know what it's for. Looking into the platform, I think bearing balls were visible. Maybe it's designed to come apart like this for servicing.

2 parts other view

Here is an exploded view: I can't seem to upload the picture I extracted from this pdf. The two leftmost pieces of assembly 1 (the ring is rubber, a seal I guess) are on the crank, the other pieces are in the platform.

I was in something of a hurry, so I just stuck it back on and used another bicycle.

How do I properly reassemble this? And while I'm at it, should I add some grease?

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  • Add a picture showing the damaged pedal if you can easily take it back off again. It's a little unclear to me from your description what exactly happened.
    – SSilk
    Commented Sep 13, 2018 at 19:27
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    @SSilk Braved the rain to take two pictures. :)
    – Nobody
    Commented Sep 13, 2018 at 19:38
  • In the first picture of your pedal (so the middle pic), there's the silver collar for a wrench to seat on, and it says "Tighten" on the side. Not sure if that's intended to be the main tightening point for the pedal to go into the crankarm, or for removing the pedal platform from the axel, as has happened to you. Does the end of the pedal axel (which is currently threaded into the crankarm) also have an Allen key (hexagonal) spot for tightening it? How did you tighten the pedal onto your crankarm? With the wrench location out by the platform, or hex location at the other end of the axel?
    – SSilk
    Commented Sep 13, 2018 at 19:54
  • PS: If you look at the instructions for this pedal, it points out the hex location at the end of the axel that I mentioned, and says to use that to install them. If makes no mention of the silver wrench collar out by the pedal platform which makes me think you're not supposed to use that for this purpose. si.shimano.com/pdfs/si/SI-46P0A-001-ENG.pdf
    – SSilk
    Commented Sep 13, 2018 at 19:56
  • @SSilk To mount/remove the pedal there is a hexagonal indentation on the other side of the crank. The "Tighten" wrench collar is not used for that and I have never turned it.
    – Nobody
    Commented Sep 13, 2018 at 19:59

2 Answers 2

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I found a component diagram for these pedals here.

Here's the main diagram:

enter image description here

Looks like all the bearings are mounted onto the axle and secured with a bearing preload and lock nut at the outboard end. The axle and bearing assembly is then threaded into the pedal using the threads on part 2 - that's why the torque spec is printed on its shoulder.

Obviously the retaining nuts came undone. All the balls, cones, bushings and nuts should still be in the pedal body as part 2 should have stopped them from falling out.

If you un-thread part 2 you can get all the balls, cones, bushings and retaining nuts out. I'd do this over a tray or box to catch the balls and small parts that will fall out. You can then reassemble the bearings and, then thread the assembly back into the pedal body.

You could try re-inserting the axle, un-threading part 2 and see if you can withdraw the bearings etc on the axle.

Update:

You should examine the state of the bearings and cones to make sure they are OK before proceeding with reassembly. Maybe something seized which caused the retaining nuts to come undone.

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  • Nice one, style points: should they add any grease?
    – Swifty
    Commented Sep 13, 2018 at 21:09
  • @Swifty There appears to be quite a lot of grease on the axle, but to re-assemble the bearing the OP will probably need to clean some off and add more as needed.
    – Argenti Apparatus
    Commented Sep 13, 2018 at 21:11
  • @Swifty Actually, as I think about it, If I were doing this I'd clean all the grease off as its contaminated with water and probably dirt, use complete new fresh grease, AND disassemble and service the other pedal in case it's also about to fall apart too.
    – Argenti Apparatus
    Commented Sep 13, 2018 at 21:13
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    I just noticed the tip of the axle is broken off - it has an unusual rough ending and the screw part is only half as long as in the diagram. And even though it's perfectly possible to take it apart, I assume there are no repair parts available.
    – Nobody
    Commented Sep 13, 2018 at 23:19
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    @Nobody That sucks. Pedals are a current offering so an axle might not be impossible to get hold of.
    – Argenti Apparatus
    Commented Sep 14, 2018 at 0:58
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Seems to be a common problem with this otherwise fine Shimano pedal: the outside end of the axle broke off. (Because of an excessively tightened nut!?!) Had the same thing happen to me some time ago. Shimano (Paul Lange) claimed I had caused the damage when "servicing the pedal"...

Replacement axles are available in the aftermarket. But this only works if you are able to remove the outside cone and retaining nut from the inside of the pedal body.

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