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One of the most consistent themes throughout the evolution of the bicycle’s drivetrain has been “more gears.” Almost all the technology associated with the bicycle drivetrain has been developed to refine shifting function or to facilitate adding gears to the bicycle. Because, you know, if two speeds is better than one, then three is better than two, and four is better than three. Drivetrains seemed to be locked into this trajectory—always more, never less—which led to 22-speed (road) or 33-speed (mountain) drivetrains.
Today, however, SRAM wants to convince some of us that less is greater than more.
Riffing off its popular one-by (1x) mountain bike and Force CX1 ’cross drivetrains, SRAM is introducing an expanded range of 1x products pitched to gravel, adventure, triathlon/time trial, fitness, commuter, and road riders. The groups are called Force1 and Rival1. Their key technologies are the same ones used on SRAM’s 1x mountain and ’cross drivetrains, but SRAM expanded the offerings and tuned them for road-centric applications.
More From Bicycling
Because there really isn’t any new technology, I’m going to talk about the big-picture questions first, then talk tech. If you want to get a picture of what this stuff is, imagine SRAM’s Force CX1 group, add more chainring sizes and cassette options, and call it Force1. Then and add a lower priced version of basically the same group and call it Rival1. There ya go.
Do You Want 1x?
Maybe.
With 1x you are giving up something. At SRAM’s media presentation in early April, road product manager JP McCarthy stated right from the top, “We are in no way claiming a one-by drivetrain replaces a two-by.” When the number of gears is cut in half, either range or ratios are sacrificed.
You can see this for yourself at the excellent website gear-calculator.com. The site allows you to compare two drivetrain options.
I’ll get you started with a range comparison pitting a 1x11 using a 50-tooth ring and SRAM’s 10-42 cassette (more on this later, but it’s the same cassette used in SRAM’s existing 1x mountain bike groups) against a 2x11 group with 34/50 compact rings and an 11-28 cassette
This 1x11 drivetrain has a slightly wider range than the 2x11, almost equal on the low gear, with a taller high gear and bigger steps. With the 2x drivetrain, the rider can keep it in the small ring for the first four cogs, then shift to the big ring and big cog when the ratios overlap (ignore surly mechanics: if the chain is long enough, big/big cross-chaining a modern drivetrain is fine). This gives the 2x11 drivetrain 15 ratios. (Technically, it’s about 18 distinct ratios, but hitting them all sequentially would involve a lot of shifting in and out of the big ring and up and down the cassette. It’s possible, but a pain in the ass and I’ve never met anyone who goes through the trouble for a couple extra ratios.)
Tighter steps with 1x are possible at the expense of range. This comparison looks at a 2x11 drivetrain with 39/53 rings and an 11-25 cassette versus a 1x11 drivetrain with a 54 tooth ring (SRAM does not make a 53t 1x ring) and 11-25 cassette. No surprise, the 1x has almost identical steps to the 2x in the 53, but 1x loses the low end of the range.
You can play with gear-calculator.com to compare all sorts of possible permutations, but the results are always essentially the same:
* A 1x drivetrain with the range of 2x, but larger steps.
* A 1x drivetrain with the same steps as part of a 2x range, but a narrower range than 2x.
Adding the additional complication of a second derailleur, chainring and shifter on a bike just to get four-ish (depending on overlap) extra ratios can seem a bit silly. Or not. Your situation will dictate your best path.
For example, some of my co-workers and I find that for competitive road riding, having smaller steps is preferable because it reduces the chance of feeling like we’re jumping between ratios that are a little too low/a little too high when trying to maintain a cadence/perceived effort/power target.
But the simplicity of 1x is appealing also. My Seven Axiom SL do-everything-but-race bike has 36/52 rings with an 11-32 cassette. I could get a similar range using a 48-tooth ring and 10-42 cassette and a simpler drivetrain.
I’m sure I’d encounter some situations where I’d miss the additional ratios offered by 2x, but I’m also reasonably sure that that those situations would be easily tolerable considering the Seven’s purpose. I’d think it would be the same for gravel, adventure, fitness, and commuter bikes: Having the same range with fewer parts and a simpler setup seems like a pretty good deal, and worth giving up a few ratios.
It’s also easy to imagine circumstances where a tuned-and-tight range would be an advantage. Bikes honed for a specific use or course—criterium races, triathlons and time trials, even a climbing stage or flat road race—might only need a very narrow range of ratios. With a ring and/or cassette swap, SRAM’s 1x drivetrain’s gearing can be tuned to a specific demand, resulting in a simpler drivetrain that eliminates redundant and unused elements.
To do this tuning right, however, the user would likely need to do a lot of chainring- and cassette- (and maybe chain-, which I cover below) swapping for different courses and training situations. This can be a pain. With 2x, you’re always carrying everything you might need.
Beyond the Number of Gears
Range and ratio aside, SRAM says there are advantages to 1x. It’s simpler (and more “pleasant,” says McCarthy) and it creates a cleaner looking bike because the inner chainring, the front derailleur, and its cable and housing are eliminated.
This might also make the drivetrain a bit lighter. McCarthy says the average weight savings for Force1 versus Force 22 (the 2x11 group) is 170 grams. The 1x rear derailleurs are heavier than their 2x counterparts—Force 22 medium cage, 187g, Force1 medium cage, 261g—but because of the reduced front drivetrain system, the total result is a weight reduction. However, McCarthy’s 170-gram claim is assumes the same cassette. The 1x’s weight advantage starts to erode if a bigger (heavier) cassette is used to recoup some of the lost range. SRAM does not yet have an estimated weight savings for Rival1 versus Rival 22 but it expects it would be greater than 170 grams (with the same cassette).
Cautioning that SRAM’s data is far from complete, McCarthy says that there is an aerodynamic advantage to 1x because the cable and housing, front derailleur and hanger, and inner ring are eliminated, but the gains are somewhat offset by the larger 1x rear derailleur. SRAM has no data to share at this point, but hopes to have more complete data in the future.
McCarthy touted another advantage, one that I have yet to feel on a mountain or ’cross bike with a SRAM 1x drivetrain. The “chain and chainring interface is so secure, it gives the bike a different feel,” he says. “It feels more efficient.”
“Is that true?” I asked. When it comes to rings and cog, bigger is more efficient. “True, a larger ring with the same gear ratio is more efficient,” says McCarthy. “The reason is that the smaller ring has a higher tension, which results in higher friction.” SRAM’s preliminary and limited efficient testing, done by an outside agency, reveals that difference in efficiency is a “fraction of a watt,” at a 270-watt input. SRAM is building a test machine in its Coimbra, Portugal, chain factory to explore efficiency questions more completely. I hope to have more information to share in the future.
Meet Rival1 and Force1
We’ve covered SRAM’s 1x drivetrains for mountain and ’cross before, so I’ll skip the deep tech dive for a shallow wade.
The technologies below already existed in SRAM’s universe. And they already had a drop-bar 1x drivetrain called Force CX1. All that’s really “new” with this batch of products is a wider offering of 1x products. What was called Force CX1 becomes Force1 and it is accompanied by a lower price Rival1 group. There are also a few non-series parts like a flat-bar shifter for SRAM road 11-speed derailleurs, and a lower-end crank aimed at fitness and commuting bikes. For time trialists and triathletes, SRAM’s 11-speed bar-end rear shifter will be sold separately.
What Makes It Work
The crucial features that make SRAM’s 1x drivetrains secure are found in the rear derailleur and the chainring.
The chainring has alternating thick and thin teeth, which grab the chain’s link plates, locking the chain on the ring without any supplementary retention. It seems too simple to work, but so far it has worked well for my co-workers and me. A few of us have dislodged a chain on longer travel full suspension bikes in very rough terrain, but these incidents are very rare.
The rear derailleur uses a straight parallelogram that can only move laterally, making it impervious to ghost-shifting in rough terrain, says SRAM, and providing lighter shifting action. The pulley cage has a one-way clutch that damps its forward rotation and reduces chain bounce. Like the chainring, the pulley teeth alternate thick/thin.
XG Cassette
A very important piece of SRAM’s 1x system is the 10-42 11-speed cassette. Without this cassette, SRAM’s 1x groups would not have been embraced as widely by mountain bikers. It provides both the low and high end necessary to make a single-ring drivetrain a viable alternative to 2x.
This wide range cassette has existed in the SRAM universe since the launch of the XX1 mountain bike group in 2012, but until Force1 and Rival1, SRAM did not have a derailleur compatible with their drop-bar shifters with enough capacity for this cassette. Presently, this cassette cannot be used with SRAM’s multi-ring drivetrains.
Though it’s just one tooth smaller than the 11 already found on many cassettes, the 10-42 cassettes requires a new cassette driver standard called XD. It’s required because the diameter of the standard Shimano/SRAM driver body limits the smallest cog to 11 teeth. It’s a lot of hassle for one tooth, but McCarthy says the effort is worth it, “for added range, where added range is necessary.”
Many wheel and hub companies offer XD drivers for their mountain bike products, so making the driver for road hubs and wheels should not be a stretch. While Zipp (owned by SRAM) does make a XD driver for its 77/177D disc hubs (found on the 202 Disc, 303 Disc, and 30 Course Disc-brake), it does not make one for the hubs used on its rim-brake wheels.
A second 1x-only cassette, this one an 11-36, also exists in SRAM’s parts catalog. This is the widest range cassette SRAM offers for the standard 11-speed Shimano/SRAM cassette driver body.
Since the cassette is not 1x specific, just about any 11-speed cassette and any SRAM/Shimano compatible 10-speed cassette will work.
What You Need to Know
* The significant differences between Rival1 and Force1 are weight, materials, and finishes, and not functional features.
* Force1 and Rival1 are not new groups, but expansions of the existing Force 22 and Rival 22 groups. The only parts distinct to 1x are the rear derailleurs, chainrings, and two cassettes: the 11-36 and 10-42. All of SRAM’s current 11-speed chains are compatible with the 1x groups. SRAM’s 2x11 groups—Force 22, Rival 22 and Red 22—are unchanged.
* Only a rear derailleur and chainring are required to convert an existing SRAM 2x11 drivetrain to 1x11. The left shifter won’t be connected to anything, but if that bugs you, the hood can be gutted. In a completely shocking bit of user-friendliness, the Rival1 and Force1 rear derailleurs are backwards compatible with SRAM’s 10-speed drop bar shifters.
* 11-speed cassette options are 10-42 (requires a long cage derailleur), 11-36, 11-32, 11-28, and 11-26 (requires a Force1 short cage derailleur). The widest range 10-speed cassette SRAM offers is an 11-32. A SRAM cassette is not mandatory, so any Shimano 10- or 11-speed cassette will work. So will IRD’s wide-range cassettes, offered in 10-speed (11-28 up to 11-42) and in 11-speed (11-30 up to 11-42); and the Praxis Works 10-speed 11-40. So far, only SRAM offers a 10-42.
* Force1 chainrings are offered in 38-, 40-, 42-, 44-, 46-, 48-, and 50-tooth for 110 BCD; 52 and 54t for 130 BCD. Compared to last year’s Force CX1 rings, the new rings are slightly modified to improve durability, “by manyfold,” and to run quieter, McCarthy said. While the 38 to 50 tooth rings are likely to be used for cyclocross cross, gravel, or adventure riding, the 52 and 54 tooth rings probably will not, so SRAM eliminated the mud evacuation ports found on the smaller rings. Eliminating the ports made the rings stiffer, said McCarthy. Force1 crank arms are carbon, and offered with both a 110 and 130mm BCD spider. The spider may be removed and changed to a different size. The cranks are offered in 162.5, 165, 170, 172.5, 175, and 177.5mm lengths, BB30 and GXP axle.
* Rival1 chainrings are offered in 110 BCD 38-, 40-, 42-, 44-, 46-, 48- and 50-tooth only, with no 130BCD options. Rival1 crankarms are aluminum and sold only with a 110BCD spider. However, the Rival1 crank uses the same removable spider interface as the Force1, so it is possible to upsize the spider. The cranks are offered in 162.5, 165, 170, 172.5, 175, and 177.5mm lengths, BB30 and GXP axle.
* The derailleur’s pulley-cage pivot is placed so the upper pulley moves vertically as the cage rotates. This keeps the upper pulley close to the cogs for better shifting, says SRAM. It also means the system is sensitive to chain length. More than a 2-teeth-up or 4-teeth-down change in chainring or cassette requires chain resizing.
* SRAM offers Force1, Rival1, and 10-speed left levers for hydraulic and mechanical brakes with the front shifting mechanism deleted.
How It Rides
I had an opportunity to ride a Santa Cruz Stigmata CC ’cross bike fitted with Force1, a 40-tooth ring and a 10-42 cassette outside of San Luis Obispo, California. The 40-mile route included plenty of climbing and descending on open road, and paved fire roads, but most of the riding took place on dirt fire roads—some of them quite steep—that ranged from smooth to very rough, thanks to ruts from recent rains.
I went as slow as 7mph on some climbs, and reached a 38mph maximum speed. The range was impressive, letting me spin easily up the steepest bits (a bit more than 16 percent in a few places) and gave me plenty of gears for almost everything else. I did, however, nearly spin out on a fast, paved, tailwind-aided descent. I never once thought the steps were too big. But this was largely a social pace gravel ride, and not the situation where I’d want tight steps. Shifting was exactly what I experienced when I rode Force CX1: crisp with a smooth and light—but not too light—effort. Despite some rather jarring rain ruts, I didn’t drop a chain, and neither did any of the other 11 1x-equipped riders in my group.
1x for All?
I polled a few of my co-workers to see what they thought about a 1x drivetrain for their riding. I got a diverse range of reactions, one of them being, “If SRAM could make their front shifting as good as Shimano’s, they wouldn’t need to push 1x on us,” which is harsh, but not entirely unfair. However, the best front shifting in existence is found in Shimano’s electronic Di2 groups, which are expensive and complex.
On the other end of the spectrum from Mr. Grumpy was a rider who said, “I’m kind of psyched to try 1x. What was the last technological development that actually simplified the bicycle?” We’ve grown so used to new equaling more. It is actually quite refreshing to have something come along that makes a bike simpler and cleaner, without any compromise to the bike’s purpose or capabilities. Really, the only sacrifice 1x asks us to make is to spin a bit faster in some gears and grunt a little more in others.
I think many might see 1x as a competitor to 2x. I don’t think of it that way. 2x has a place. 1x has a place. Hell, 3x has a place. There isn’t one answer. We are riders with needs and wants; this gives all of us more options to fulfill them. It’s less than you had before, but it could be all you need.
Availability and Pricing
McCarthy says that the new 1x parts will be available aftermarket in mid- to late summer. Bike brands will take delivery in May and there are at least 35 brands that will offer bikes with Force1 and Rival1 drivetrains.
Force1
Right lever for hydraulic brakes $375; for mechanical brakes $190
Left lever hydraulic $315; mechanical $87
Derailleur: $231
Chainring $82 to $99 depending on size
Cranks: $201 to $322 depending on axle and chainring size
Rival1
Right lever for hydraulic brakes $355; for mechanical brakes $123
Left lever hydraulic $284; mechanical $155
Derailleur: $120
Chainrings: $tk to $89 depending on size
Cranks: $168 to $196 depending on axle and chainring size
SRAM 11 speed cassettes
PG1170 $100-$110 depending on size
PG1130 $64-$88 depending on size
XG1190 $351-$374 depending on size
XG1199 10-42 $445
XG1195 10-42 $369
XG1180 10-42 $313
XG1150 10-42 price not available
