Ball bearing narrow-wide bicycle derailleur tensioner jockey wheel

I bike a lot, and have been blowing through derailleur sprockets like once a season. The planar bearings they use don't like the grease I have, so I figured, why not make a sprocket that uses a replaceable 605ZZ ball bearing I have in my supplies? 

My bike has a Shimano 105 short/medium gate derailleur fitted, but this should work for any 11 speed or lower derailleur. Just make sure it will fit inside any tabs on the derailleur cage. This sprocket has an extra tooth and narrow-wide tooth spacing to help lower chain slap; be sure to align the thicker tooth with the wider chain links. It just clears the chain tabs on my derailleur.

This print requires supports. If you are able to print with soluble supports then you will end up with a better print and less finishing work to do. If you use regular supports, then expect to be doing some light filing on the supported side of teeth to get things to fit nicely. It might make a little bit of noise for the first couple of minutes of riding, but should wear in quickly. If your chain jumps and catches you have more cleaning or printer tuning to do.

I've been quite happy with the PLA prototype that I'm currently running with about 100km on it so far, though I will mention that I also have a polycarbonate print ready to go in my kit. I will post how long the PLA one lasted if/when it dies.

Recommend printing with a MINIMUM of 3mm wall thickness, so 8+ layers with 0.4mm nozzle, I used 6 layers with a 0.6mm nozzle. Printing with 99 layers ensures a solid part.

After printing, you will need to press the 605ZZ (NOT 608ZZ) bearing into place; I use a small vice and a socket, but a C-clamp (and socket) would also do the trick. Mounting it in the derailleur is a little tricky as you need two 5mm washers on the bed side and one 5mm washer on the other, for a total of 3mm of spacer. I use a tiny drop of crazy glue to help hold things together; don't get glue in the bearing. The final assembly should be 8mm thick.

This 0.5" chain pitch is used pretty much exclusively on bikes, so in theory this could work on any bike chain that fits on the teeth. Feel free to play with your Z scale to fine tune it to your chain (cutting the STL and adding a subtractive cylinder helps reduce print times for testing the tooth thickness).

Leave a comment if you want different tooth counts and I'll add the files. If you are not comfortable changing your own derailleur sprockets then I don't recommend you try this print. It is common practice to put Loctite on the screw threads for the jockey wheel fasteners, be sure to match whatever you took off.