willydstyle

Let's say I want to keep my current wheel, which is a 20" folding bike wheel, what options do I have on this hub? Let's say I want to upgrade to 10s cassette/chain/shifter, maintaining a single chainring, on flat bars, what are my options?

Andrew R Stewart 

First you have to see if the freehub body is long enough to fit the 10 cog cassette. This is best done by an actual measurement and not relying on some spec chart found on line. If you can't remove the cassette and do this measurement than any bike shop could help you with this. After this initial discovery the rest will be rather straight forward, unless there's other odd stuff going on. How does your current der attach to the frame? Does the shifter integrate with the brake lever? Andy

willydstyle

I do have a spare 10-speed cassette that I could just throw on there and see I suppose. I do currently have a claris integrated shifter/brake lever so my plan was to replace both of those as well. I was thinking the Shimano Zee groupset would be nice because it's compact which seems better for small-wheeled bikes. Can pretty much any shimano 10-speed shifter work with any shimano-compatible 10-speed cassette?

alcjphil

You have to match the shifter to the derailleur. A 10 speed mountain bike shifter will not work with any 10 speed road derailleur. The cassette is not the important part of the puzzle

70sSanO

This is the part that gets confusing, especially with flat bar shifters.

For many years Shimano index “rear derailleurs” had a standard ratio for both mtb and road. For 10 speed mtb Shimano went to a different rear derailleur ratio with Dyna Sys. Shimano’s current 10, 11, 12 speed shifters have moved even further away from the old standard.

That said, if you have Claris shifters and want to go to 10 speed rear cassette, if it fits, I believe the only flat bar shifter that will work is a Tiagra 4600. New shifters are still available from a few sources and eBay.

There is a caveat that your current rear derailleur can handle the maximum cog of the new cassette; i.e. 32t, 34t, 36t, 40t, 42t, etc. if you need a larger max cog than you have now, so you can pedal easier, you may need to go to a “9 speed” Deore mtb rear derailleur to work with a Tiagra 10 speed 4600 road shifter. As odd as it sounds that is the way it works.

All this does bring you back to Shimano Zee or other 10 speed mtb Dyna Sys. If you have to change both the shifter and the rear derailleur anyway, it is better to use a mtb 10 speed (Dyna Sys) and forget about any of the road stuff you have now or mixing 10 speed road with 9 speed mountain.

John

Andrew R Stewart 

One rarely anticipated issue with swapping rear ders on a 20" wheel is the tension pulley to ground clearance can become less than ideal... Andy

70sSanO

Good point I hadn’t thought of.

I’ve added a RD hanger extension of a larger 26” mtb wheel and even that has given me pause to what might happen in the wrong terrain.

John

hokiefyd 

I have a bike with a 20" wheel and I've had, at largest, a 12-36 9-speed cassette on it. This bike has a short cage derailer (an RD-M340) to improve ground clearance, and it was definitely needed when on that 36 tooth sprocket.

willydstyle

So this is the hypothetical parts list I have put together, assuming a 10-speed cassette will fit in my frame:

Shimano BL-T611 brake lever
Shimano HG50 cassette 11-36T
Shimano SL-M640 Zee 10 speed shifter
Shimano RD-M640 Zee 10 speed derailleur (the higher capacity model for up to 36T cassette)
Edit: I'll need a 10 speed chain too, but it seems like most shimano/sram/KMC chains are going to be compatible with a shimano 10 speed cassette

Does anyone see any glaring incompatibilities here or any opportunity to get a better value part? I'm picking the Zee because it is marketed as being a compact derailleur for its capacity, but I'm not 100% invested in getting it. Similarly I picked the Zee shifter because it seems relatively inexpensive and it seems guaranteed to be plug-and-play with the derailleur.