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The outer pulley of my RD-M735, when spun, sounds scratchy and feels slightly grindy as if there is a tiny piece of dirt/grit that has fallen inside.

I have literally soaked it in WD-40 and then 3-in-1 oil and also, motorcycle chain oil (scottoiler oil), whilst spinning the pulley and it is a lot better than before. But it still catches now and again when turned by just finger tip, and sounds slightly dry and grindy. It will turn under two finger pressure though.

Therefore, I was wondering if the pulleys are serviceable, inasmuch that one can access, clean and repack with grease, the ball bearings, or replace the bearing (that I presume) are/is within the axis of the pulley?

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    Vintage jockey wheels are indeed servicable as they are often equipped with ball bearings (not sealed). Modern either are with bushings (sleeve bearing) or sealed bearings. The former I'd directly replace with those with sealed bearings. Sealed bearings can be cleaned and repacked with grease. Or simply replaced. So yes, it is possible, however sometimes not worth the effort (worn out bushings).
    – Mike
    Commented Oct 4, 2018 at 19:50
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    Used to be you could buy replacement jockey wheels from several sources. I haven't seen them advertised for several years, though. (But partly this is because printed catalogs have gone the way of the dodo.)
    – Daniel R Hicks
    Commented Oct 5, 2018 at 0:00

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Yes, the pulleys of your rear derailleur can easily be removed, cleaned, greased, and re-lubricated. I'd recommend doing so about every 500 miles depending on your climate or whenever they start to sound gritty again.

If you haven't yet, I recommend reading all the Park Tool drivetrain care topics.

Steps 9 through 13 particularly on this page should cover the pulleys:

https://www.parktool.com/blog/repair-help/rear-derailleur-overhaul

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  • Just want to add that, when disassembling, it is recommended to remember/mark which pulley wheel is which (top/bottom), and which direction they rotate at, as sometimes they are not unidirectional, and lower one is different from the top one. It will help a lot at reassembly
    – Grigory Rechistov
    Commented Oct 4, 2018 at 20:03
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Yep, derailleur idler wheels are easily serviceable, or replaced if they are worn (either the teeth or the bearing).

They can be easily removed from the cage, serviced and then replaced one at a time so the cage stays in one piece and it's easy to route the chain. They tend to use plain bearings rather than ball bearings so they are easy to clean and re-lubricate. Note the top and bottom idlers are different - which is another reason to deal with them one at a time. The top one usually has some lateral movement to align with the cassette sprockets.

GCN video on idler servicing:

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