Ask a Mechanic: Converting to SRAM 1X Road Drivetrains.

Daniel asks, “ I’m thinking about getting SRAM’s 1x road drivetrain for my ‘cross bike but I’m not sure what gearing I should run. Can you offer some advice on that?”

With cyclocross season right around the corner, this is a common question. Using SRAM’s road 1x system on a ‘cross bike makes complete sense, as many ‘cross racers have been racing on a 1x set up for years, but now they have a couple factory-dedicated 1x groups, which includes their new Rival 1 groupset. For road use, 1X drivetrains are great for time triallists or triathletes, criterium racers, and commuters. Sram’s 1x groups for your drop bar bike have been around for about a year now, but there is still some confusion as to what size chainring and cassette most people should be riding.

When selecting a chainring, 40 teeth is a great place to start for ‘cross racing. According to an inside source, SRAM’s top pros universally use 42 tooth rings on all but the fastest of courses. So for us mere mortals I would say that a 40 tooth, or 38 tooth chainring is a good option. Which chainring you run is also influenced by the cassette you choose.

Most pros running the 1x drivetrains are running an 11-32 cassette, but once again, they’re pros for a reason and are able to run a much higher gear than the general public. Smaller range cassettes are well-suited for time trials, pacelining and aggressive riding in rolling terrain. For ‘cross, I would say an 11-36 is a great option to start with. The 10-42 cassette is awesome if you’re really looking for a low climbing gear, but be aware that if you choose to run this cassette, you will need a wheelset that is capable of accepting an XD driver freehub body. The benefit to running that cassette however, is that you will be able to have a 1 to 1 gear ratio with just about any size chainring that you choose to use. When choosing your cassette, keep in mind the gear range capacity of the rear derailleur cage length that you need. Long-cage 1x rear derailleurs are made for SRAM’s 10-42 and 11-36 cassettes, and the mid-cage derailleurs are made for cassettes that range from 11-28 up to 11-36.

So whether you want to simplify the drivetrain on your road bike, or are looking for the ultimate set up for your cyclocross bike this racing season, take a look at the dedicated 1x system from SRAM. Hopefully this will help make choosing your gearing a little simpler and clearer. Have fun and good luck in the upcoming race season.