A few weeks ago I made the switch over to a single front ring to make my cyclocross bike a 1 x 10.
I’d been considering it and sizing up my options for a while but when the new X9 rear derailleur was delayed I pulled the long cage X0 type 2 from the trail bike and used it instead. That was almost identical to the X0 rear derailleur I had been running but with the necessary clutch to keep the chain engaged. I’d purchased both 40t and 42t front rings and opted for the 42t as I felt most often I’d wanted to stay in the big ring rather than switch down to the 36.
Out back I’d been running an 11-32 cassette which works out to be slightly lower than the 34t x 28 I had been running on this bike previously, so in my mind that lower cassette is really what makes this possible. On flatter courses I’d consider running a 28 or 30 as well, but only after a thorough pre-ride to be sure.
It’s worth mentioning that racing and training have different requirements, and the single ring does limit the versatility somewhat. Tim Johnson races on a SRAM CX1 single ring but trains on a double and has stated he’d consider racing a double under certain conditions. My mountain bike background means I’m more used to pushing big gears and keeping traction where others may prefer to spin; with most climbs in ‘cross being short and punchy I felt the risk of being overgeared to be minimal.
The recent Shedd Park race course featured two very sharp but rideable run up sections, so that’s about as much steep vertical as I’ve seen on any course and I had enough of a low gear to clear those when not riding in traffic. Extreme mud may be a different story, but if it’s that slick it’s likely to be a forced dismount anyway. On the faster sections of the course I really liked being always in the right gear up front whereas I often felt in between with the 36/46. This was helpful especially exiting corners and on up & downhill transitions.
With a Raceface Narrow/Wide chainring, the aforementioned X0 derailleur, and proper chain length I never dropped the chain once though I did mount a SRAM Red chain catcher to the braze on mount with some scavenged Thomson seatpost parts and an M4 bolt from the hardware store.
For flattish trail and road riding the single ring is fine and I never wanted for more. On a particularly steep and snowy dirt road ride I felt a little over geared, but that’s really the only time I felt that way. Given that most off season rides avoid prolonged steep sections it’s usually a non-issue, but once I fully commit to training mode I’m likely to switch back to the double up front.
It’s worth noting that the 1x is inherently better suited to extreme mud or snow and ice buildup as shown in these pictures from my ride on Thanksgiving Day. Front derailleurs are more prone to jamming and in conditions such as this and they’ll often leave you with just one chainring anyway. Shifting and general drivetrain operation were largely trouble free in spite of the massive ice buildup, though the cassette did collect some to make the smallest cog unusable.
In the same conditions Carrie had more drivetrain issues with her Force/Rival 11 speed combination and had the same snow buildup problem in the cassette, but the tighter spacing between cogs meant that she lost the use of more gears than I did. When I spec’ed out her bike I went with the new 11 speed because it was actually cheaper than 10 speed and I knew it would be easier to get parts for it going forward. That’s mostly been the right call as the overall performance of that group has been great, but not great enough for me to endorse dumping a perfectly good 10 speed setup- especially for racing off-road.
Same story out back, too.
I didn’t realize quite how bad the buildup was until later- notice how the ice has been shaved by the chain catcher. Oh, and the Stages Power Meter still worked fine, too.
Overall I think the 1x option is great for racing and offers simplicity along with consistent performance. To get the most out of it I would recommend the wide range 11-32 cassette and a 40t or 42t out front. You could swap out the cassette to an 11-28 or 11-30 for flatter races or even swap around rings as low as 38t or 40t and as high as 44t or 46t. For me the 42t is just about right. It’s slightly less awesome for really rolling courses or for training rides on variable terrain where longer climbs and descents abound. It will still work there of course, but you’ll be wanting gears further apart rather than all accessible right in the middle.
To make this setup work you’ll need new school narrow/wide chainring (like Wolf Tooth, Raceface, or Absolute Black) and a clutch type derailleur (X7, X9, X0, XX, XX1, Xo1, X1, or CX1) though going with one of the latter 1x specific models will limit your ability to go back to a double. I’ve heard reports that the 10 speed X9 works fine with 11 speed drivetrains though I’ve not confirmed it myself. I’ve also heard reports that you can run a standard short cage 10 speed road derailleur (non-clutch) with a short enough chain and have no issues dropping the chain, provided you have a Wolf Tooth Components or other similarly tall profile chainring. My suspicion is that it would only really work if you ran a really tightly spaced cassette to keep the chain slack at a minimum.