SRAM X1 Drivetrain, Part 1
Specs: 2014 SRAM X1 Group
(shifter, derailleur, crankset, cassette, chain)
Mounted to: Canfield Yelli Screamy (29er)
Total Measured Weight of Groupset: 1,733 grams
Intended Use: wide ranging, single-ring riding
- 10-42 XG-1180 Mini Cluster Cassette
- 11 Speed X-HORIZON Rear Derailleur
- 1400 Hollow Forged X-SYNC Crankset
- XD Driver Body
- 30, 32, 34, 36 or 38 tooth X-SYNC Chain Rings
- PC-X1 chain
- 11 Speed Trigger Shifter
Duration of Test: 35 days
Locations: In and around Whitefish, MT
Reviewer: 5’9” 150lbs
SRAM’s XX1 11-speed drivetrain system has been around for a couple years, and SRAM now makes the XO1, an extremely similar, slightly less expensive group that is being put on complete, more affordable bikes than those bikes built with the top-end XX1. But the XO1 is still a fairly expensive drivetrain found on fairly expensive bikes.
With the introduction of the X1 group, SRAM is making a second push at that cost barrier, with another 11-speed, single-ring drivetrain meant to be more attainable to those that don’t bathe in fur-lined vaults filled with gold coins (or whatever the fabulously wealthy bathe in).
This review of the X1 is split into two parts: Part 1 (which you’re reading right now) orients the X1 in the broader scheme of drivetrains in terms of it’s weight and price, and compares it to 10-speed options. Part 2 discusses how the X1 system performs on the trail.
Gearing & Gear Inch Ratios
When it comes to gearing, the pros and cons of 11-speed, single-ring systems have been discussed at length by countless representatives from the kingdom of bike nerdery. But for those that haven’t paid much attention to it, here’s the gist in a very small nutshell: switching to an 11-speed drivetrain sacrifices a bit of the range that you’ll have on a standard 2×10 setup, but it’s almost the same.
The different gears on a bike can be measured a few different ways, but the most common (at least in the U.S.) is with a value called “gear inches” or “gear inch ratio.” This number is calculated using the diameter of the wheel on your bike, the number of teeth on a front chainring, and the number on a given cassette cog.
Gear inch ratio = (diameter of drive wheel x number of teeth on the front sprocket) ÷ number of teeth on the rear sprocket)
Easier gears have lower gear inch ratios, and harder gears, those that require more force to crank over, have higher ones. (If you’re interested in a more lengthy discussion on this topic, see Sheldon Brown’s Bicycle Glossary.)
With this in mind, let’s compare the ratios found on the 11-speed X1 to those on a 10-speed setup (assuming we’re running them on a bike with 29” wheels). A fairly common chainring configuration on a 2×10 setup uses a 24-tooth small chainring and a 36-tooth large chainring, and a common 10-speed cassette might have an 11-tooth small cog and a 36-tooth large cog. The gear inch ratios on this setup range, then, from 19.3 inches [ (29 x 24) ÷ 36 ] in the easiest gear, up to 94.7 inches in the hardest gear. That means the total gear “range” is 75.4 inches.
Comparing this to an 11-speed setup with a single 32 tooth chainring and a 10-42 cassette (which is the gearing that I rode with the X1 kit), the gear inch ratio ranges from 22 inches in the easiest gear to 92.6 inches in the hardest, yielding a total range of 70.6 inches.
While those numbers might seem somewhat abstract, this ought to demonstrate how close an 11-speed setup can be compared to a more traditional 2×10 system in terms of gearing. With a 32-tooth chainring, the easiest gear on the 11-speed is a bit harder than that of the 2×10—to get down to that super easy 19.3 ratio with an 11-speed setup, you’d need to move to a 28-tooth chainring (which isn’t an option on the X1 cranks, but it is an option on the XX1 cranks)
However, the more important number here is the gear range; our normal 2×10 setup covers a range of 75.4 inches, while the 11-speed X1 setup covers 70.6 inches. That’s pretty dang close. And if your particular riding style needs easier or harder gearing, that range can be shifted down (made easier) by running a smaller chainring, or shifted up (harder) with a larger chainring.
For reference, the 32×42 easy gear (22 inches) that I’m running with the X1 is roughly equivalent to the easiest 24×32 gear on a 2×10 (19.3 inches). So on many 2×10 setups, that 22-inch gear would be the second easiest gear. In other words, if you’re running a 10-speed setup and you can live without your easiest gear and your hardest gear, an 11 speed setup will still cover everything in between.
Ok, that’s not quite true. With many of the 10-speed setups, cogs in the high gears are usually different in size by two teeth (i.e. the cassette progresses from a 12 tooth cog, to a 14, to a 16, etc.), and the gaps increase to 3 or 4 teeth in the lower, easier gears. 11 speed cassettes generally follow this same pattern at the high end (starting with a 10 tooth cog, then a 12, 14, 16, etc.). However, the gaps are larger in the easier gears on an 11 speed cassette; there is a 6 tooth difference between the last two cogs, which have 36 and 42 teeth respectively. So, if we’re splitting hairs, an 11 speed cassette doesn’t provide exactly the same gearing sequence throughout its range.
For people that prefer to sit and spin, this is potentially problematic. It can be a bit tougher to find that perfect gear to match your cadence when you only have one gear option in the front, and there are larger jumps between gears in the rear. Personally, this doesn’t really bother me at all. Most of my rides don’t involve long periods of spinning the pedals at a consistent cadence, and if they do, I don’t mind settling with a slightly harder / easier gear for a bit.