Hey everyone, I’m looking for some advice on how to make my Shimano GRX 12-speed 2x bike more suitable for mountain climbs.
Current setup: Shimano GRX FC-RX810-2 48x31T crankset with a Shimano CS-HG710-12 11-36T cassette.
- Cassette
For the 11-speed GRX groupset, it’s quite common to swap the cassette for something like an 11-42T Shimano Deore XT (CS-M8000) to get lower gears. However, for the 12-speed GRX, things are trickier. While 12-speed MTB cassettes (e.g., Shimano Deore XT CS-M8100 10-45T or 10-51T) offer a much wider range, the challenge seems to be derailleur capacity. Has anyone had success running larger MTB cassettes with the Shimano GRX RD-RX820? Any alternatives that would still be compatible? Also, I heard that SRAM 12-speed is no longer compatible, so mixing components might not be an option. Are there possibly other manufacturers? Or can I modify the current cassette or a MTB cassette somehow to make it work?
- Swapping Chainrings
Switching to the GRX FC-RX610-2 46x30T crankset seems like a straightforward option, but could I just swap the smaller chainring (the 30T) alone, or would I need to replace the entire crankset? Is it possible to go even smaller, like fitting a 29T or 28T chainring? Any advice on what’s compatible would be appreciated!
Thanks for any insights!
by fanhm
2 Comments
Smaller chainrings. That RD cant take a larger cassette.
~~Depends what you think you need more. Do you want a selection of easier gears or do you need a granny gear for that one hill that you have to get off to walk.~~
~~It’s hard to find a smaller chain ring than 30T, you could just swap in that single ring, it’ll affect shifting a bit but will work. In shimanos MTB range they have smaller rings 26t but at that point you are getting to a limit of the tooth difference between big/little ring so be able to shift at all. You could get an 11/12 mtb crankset which offers 36/26 front rings.~~
~~You could swap in a tiagra triple ring Shimano FC-4703 Tiagra Triple Crankset – but again it’s smallest is 30T and you’d need the shifter to go along with that.~~
Get tires with a smaller diameter.