SRAM's new CX1 single-ring components for cyclocross can be bought as a partial group, with Force 11-speed shifters or in individual parts. We tested the CX1 clutch derailleur on a bike with older 10-speed SRAM Force shifters and, for the most part, it worked like a charm. Over the course of a few weeks, we tested first just the derailleur, cassette and chain with an Absolute Black narrow/wide chain ring. Then we tested the same set-up, but with SRAM's CX1 ring, where the centered offset helped the chainline noticeably.
In both configurations, shifting was crisp and the clutch derailleur delivered on its promise: the chain simply doesn't come off the ring, even when roughly dropping or even crashing the bike. There was a bit of chirping at the Absolute Black ring when the chain was in the extreme ends of the cassette, but chainslap was nonexistent with that 42t model; using the CX1 chainring cut down on the noise as it is centered on the spider, but the smaller 38t did result in a little chainslap.
CX1 clutch derailleur + Force 10spd shifters + Absolute Black chain ring
One tester had a bike already set up with a single ring, using a 42t Absolute Black ring, a SRAM Rival derailleur and an 11-28t cassette. Swapping in the CX1 clutch rear derailleur, new chain and CX1 11-32t cassette for use with the original SRAM Force 10-speed shifters was the first test.
Since SRAM’s 10- and 11-speed road shifters have the same actuation ratio (i.e. the ratio of cable pull to lateral derailleur movement), the shifting worked fine — seemingly better, in fact, than with the Rival derailleur, perhaps because of a stronger spring and the taut chainline from the clutch.
To optimize the chainline at both ends of the cassette, the chain ring was installed on the inside of the spider, as mounting it on the outside resulted in some friction when cross-chained in the larger cogs. "The main thing I learned from that is that chainline is important," one tester said. "When mounted on the inside, there was a little drag when in the 11t, but this otherwise solved the issue. It doesn't look good mounted on the inside, though."
CX1 clutch derailleur + Force 10spd shifters + CX1 chain ring
The next change was using the CX1 chain ring (a 38t model), which, being purpose-designed, is slightly dished to place the narrow/wide teeth directly over the center of the spider when mounted on the outside. SRAM provides little washers, too, so you can just use your existing chain ring bolts designed for two rings.
In terms of gearing, the X-Sync rings come in 38, 40, 42, 44 and 46t options. The 38t proved to be adequate, especially when paired with the 11-32 cassette.
"I think I 38 is great for ’cross," one tester said. "How often are you going to be in the 38x11? Maybe at the start for four or five seconds. Plus, I did a ride this weekend with 5,000ft (1,500m) vertical, and it was great; I had plenty of low gear."
Although the CX1 X-Sync ring largely reduced the noise, there was still a bit of quiet purring, especially when the drivetrain is clean with minimal lubrication. The noise comes from friction as the chain leaves the wider teeth. (The X-Sync ring, like all narrow/wide rings, has alternating skinny and wide teeth to help keep the chain on the ring.)
"I have noticed the same thing on my XX1 chain rings," our tester said. "It seems to go away with more lube — or just a little more grime from riding."
Bottom line - A legit one-by option
Our tester came away impressed overall with the partial group and its performance with 10-speed SRAM shifters. Were he to buy his own similar set up, he would get the CX1 derailleur and 11-32t cassette, but probably get a third-party ring from Wolf Tooth or Absolute Black with a Shimano Dura-Ace chain. "That is what I have done with the SRAM XX1 on my mountain bike, and it works really well. My experience with XX1 chainrings makes me feel like they wear quickly and they are sensitive to lubrication."
The clutch derailleur keeps the chain on, whatever cyclocross threw at it.
"I used to ride 42 by 11-28 because that was what my derailleur could handle. It made steep stuff a walk," our tester said. "With CX1, the shifting is great, and 11-32 is a sweet range. It suddenly makes the single ring set-up have latitude."
Check back soon for an updated review of the complete SRAM CX1 group that has been put through its paces on the cyclocross course.