SHIMANO SERIES INTRODUCTION
Twelve rear cogs may be the big story for Deore, but Shimano has in fact released three versions of Deore: M6100, M5100 and M4100, which are 12-, 11- and 10-speed respectively. In many ways, the new 11- and 10-speed options are designed for the OE market, while also bolstering Shimano’s replacement part options for existing Shimano 10- and 11-speed drivetrain users.
These new 10- and 11-speed options use the same gear pull ratios and chain thicknesses as the existing respective 10- and 11-speed Shimano options, and so mixing and matching is certainly an option. And you may want to do just that given the boost in range these new options provide.
Shimano Deore M5100 (11-speed) offers both 11-51T and 11-42T cassettes, with the former designed for 1x use only. That’s a noticeable update from Shimano’s previously largest 11-46T 11-speed cassette. Better yet, these cassettes use Shimano’s older HG freehub body standard (the one your old bike likely has). To use that 11-51T cassette, you’ll need the new M5100 11-speed-specific rear derailleur, something that looks almost exactly like its 12-speed counterpart.
Meanwhile, Deore M4100 provides a boost in range for 10-speed users. Those using a single chainring can use the new 11-46T cassette, and there’s an 11-42T cassette option for those on 2x setups. These new cassettes come with two new rear derailleur options: the M5120 (which has a clutch) is designed for use with 42-46T cassettes, while the M4120 (no clutch) has a maximum cog limit of 42T. Oddly, both of these derailleurs are compatible with both 10- and 11-speed shifters.
Clearly those seeking front derailleurs haven’t been left out, and both M5100 and M4100 have 2x gearing options. In both cases, the cranks only offer 22/36T chainrings, while the M5100 shift lever features Shimano’s new and simplified off-on Mono design.
No word yet on pricing or weights for these components, but you can bet they’ll be everywhere on entry-level mountain bikes.