Shimano PD-M731 Bearing Service - How To

rjsdavis

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I asked the question a while ago, about how to get into these little buggers and never did get a response. Since I did all of the hard work of working out a decent way of pulling them apart and servicing them, I had a request to pop up the pics and guidance of how to do this.

Ok - so here are the pedals I'm going to work on. I was sold these by a fraudster on eBay, that described them as "great condition". They weren't. Cosmetically they're untidy, but the axles has so much play in them, you could get a screwdriver in there and oh, the grittiness. Still, there you go.

(It's worth noting, that in these pics, the pedal on the left had already been serviced and cleaned which is why they look somewhat different).
 

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Ok, next step - strip off the cage.
 

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Next step - to remove the plastic end cap. I found an old Raleigh multi-tool. The sort that would have come in the tool pack with an old Raleigh Burner or similar. The jaws of one of the multi-tool spanner ends was just a perfect fit to get into the grooves of the plastic end cap and twist it off without leaving a mark. Fortunately, because the end cap is plastic, you shouldn't find that it's corroded or stuck on the alloy pedal body.

Having thought about this after the event, an adjustable, adjustable cup pin spanner might work also...
 

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Ok - to get the axle out, you'll need a standard pedal spanner to hold the axle still, as if you were removing the pedal from the crank. A standard 8mm socket spanner is required to undo the nut that is holding on the bearing race, washer and the securing nut onto the end of the axle. Simply undo this nut, remove the washer and adjustable bearing race, by holding a screwdriver in against each of these parts and then twisting the axle itself. When all three are removed, DO NOT remove the axle yet.
 

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Ok - once the nut, washer and adjustable cone are out, you need to slide the axle out partially - about an inch or so, to give you better access to the bearings at the adjustable cone end of the pedal out, BUT without allowing the other bearings further inside the pedal to fall out.

Therefore, ideally with a magnetic screwdriver, pop all of the bearings out from the end of the pedal and keep them separate.
 

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Once all of the bearings are out from the adjustable cup end, then you can start to remove the axle fully from the pedal.

NOTE: I recommend doing this part over a takeaway plastic tub, as some of the remaining bearings will fall out and you'll need them all unless you're replacing all of the bearings.
 

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Once all of the bearings are out from both sets of races, you'll end up with this....

Time to clean everything with a liberal supply of GT-85, which is a marvellous de-greaser. Clean everything, the bearings (unless you're replacing them), the axle, the rubber seal, the nut, washer and adjustable cone and crucially the inside of the pedal body - ready for greasing everything and re-installation. You can get a thin bit of old cotton shirt through the pedal body, and push it through with the small screwdriver to help get all of the old crud out.

Now's also the time to polish the pedal body and cage whilst everything is separate as it's easier than when the pedal is complete. Autosol is blinding for bringing back any Shimano or Campag alloy back to it's shiny best. It cleans everything - including the black alloy cage too!
 

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Ok - now to begin re-installation. A nice liberal greasing of the complete axle. I use Phil Wood waterproof grease, which helps to ensure that you don't have to do this job all that often and really helps to repel water ingress. Loads of it round the crank end of the axle and where the seal is to help keep crud and water out.

Then, probably most easily with a small screwdriver, you need to get a nice covering of grease down the inside of the alloy pedal body, onto the inner bearing race on the inside of the pedal body. Once you've cleaned all of the old crud out of the pedal body from the previous step, and looked inside the pedal body, you'll just see a small "step" where the alloy pedal body narrows in internal diameter - roughly about a third to half-way down the body. (See pic below in this post) - the bearing race "step" is clearly visible in this pic.

If you match this up with the axle itself, you'll be able to see where the bearings rest on the inner pedal body and the axle when the pedal is complete. This "step" needs to be greased, firstly to lubricate the bearing surface, but also to help drop the bearings onto when you feed them back in. Getting this inner set of bearings back in the right place, resting on this inner pedal body bearing surface and ready for the axle to start going back in, is easily the trickiest part of the whole job....
 

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Using the same small screwdriver you greased the inner bearing race with, you need to try and place each of the bearings back on the inner body race, ready for the axle. The best method I found, is to have a small magnetic flathead screwdriver, so that you can drop them in, one by one, and "peel" them off the screwdriver head into the grease to hold them in place ready for the axle.

Once you've got all of the inner set of bearings in place on the inner race, it's time to very gently, and very slowly feed the axle back in. It's very easy indeed to knock one or more of the bearings and they then fall through the inner body of the pedal and fall out the other end (therefore, ensure that you do this step over the same plastic tray not to lose any bearings!). If you knock any - go back a step and get them all back in place and then re-feed the axle through. I found on each of them, that when the axle gets close to being "in place" (you can tell from the position of the rubber seal as you feed the axle back in), it needs a bit of wiggling, jiggling and very slow twisting to get the bearings to settle into place on both sets of races (1x inner pedal body race and 1x inner axle race).

You'll know it's in place, as the rubber seal will be exactly in place, and the axle will twist nicely and fairly securely, even at this stage. If you don't get this, gently pull the axle back about an inch and try it again. If you don't get it at all, you'll need to bring the axle completely out and reset the bearings and try again - you might need a good deal of patience for this step! (Pedal 2 is always easier to do this step once you've done the first one).
 

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Okey dokey - once you've got the inner bearings sorted, and the axle nicely inserted and turning smoothly, you're pretty much there. Simply now grease the outer bearing race on the inner pedal body with loads of nice waterproof grease, and you're ready to drop each of the other set of bearings into place.

The inserted axle helps nicely to guide them back onto the outer pedal race - just make sure you don't let go of the axle and allow it fall out through the pedal whilst you're at this stage, otherwise you need to start all of the bearing placement again! When the second set of bearings are in place, simply screw on the adjustable cone with your fingers/flat screwdriver and bring it down onto the bearings to make the whole axle finger tight.

This is the stage where you want to spin the axle loads to work the grease around and make sure that it just feels "right". Ensure that you can tighten down the adjustable cone to remove any play in the axle at the crank end and keep turning it. If you've got no play, no crunching of the bearings and no "stopping" of the axle where it just can't be turned, then you've probably got the bearings in the right place and you're ready to secure everything up.

If you find that the bearing crunches or stops you from turning the axle every 2/3 axle revolutions, something's not right, and you need to make bearing placement adjustments. It will be the inner races/bearings if you're getting this that require the adjustment I'm afraid.
 

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