Many tech savvy triathletes have been experimenting with 1X drivetrains (pronounced “one by”) as a way to simplify their shifting and improve aerodynamics, but should you?
Simply put, 1X refers to the number of front chainrings on a bike. A single chainring is used—eliminating a ring, the front derailleur, and front shifter. SRAM pioneered the use of single-chainring drivetrains, first on mountain bikes, then cyclocross rigs, and more recently for triathlon steeds. Stars like 2011 ITU long-course world champion (and self-described gear-nerd) Jordan Rapp, two-time Olympic gold medalist Alistair Brownlee, and even UCI cycling world time trial champion Tony Martin, have used SRAM’s 1X systems in search of performance gains.
Eliminating half your drivetrain drops weight and means that air flow over your bike is slicker. According to Xavier Disley of AeroCoach, expect to see savings of three watts—with more up for grabs, depending on the frame, front derailleur, and crank in question.
Another upside to 1X is that you only have to remember how to shift to a harder or easier gear, especially when cross-eyed and at your limit. 1X shifting is sequential, unlike the compound shifts (both front and rear) needed on 2X systems. A 1X also reduces the chances of a dropped chain, eases packing and unpacking your bike, and creates less maintenance throughout the season.
What it Takes
For the most secure chain retention, a 1X drivetrain requires a wide/narrow chainring, where the teeth alternate in width to help retain the chain, and a rear derailleur with a clutch that increases tension on the chain.
The simplest way to go 1X is to buy one of SRAM’s well-suited 1X drivetrains. Shimano devotees will need an adapter to use the required 11-speed mountain bike derailleur. The other Shimano option is to pony up for Di2 and use a Di2 mountain bike rear derailleur. Wide/narrow chainrings from SRAM, Rotor, Wolftooth, Absolute Black, and AeroCoach are widely available, with round and ovalized shapes. Wide-range cassettes from the common 11-28T all the way through SRAM’s monstrous 10-42T compliment a single ring well.
The downside of 1X is the additional homework needed to gure out your best gear range. Ideally, you pick a chainring that keeps you in the tighter section of the cassette, reserving the larger cogs as a bailout. If you live in a hilly area or travel to areas with diverse terrain, you may need to change chainrings or cassettes frequently.
To 1X or Not?
Ultimately, that’s up to you. If you live and race in flatter areas, then 1X is an easier choice. If you don’t mind frequent chainring and cassette swaps, 1X drivetrains can offer a range for nearly any tri. Just be sure to research your gearing needs before taking the plunge. “Everyone I know who shifts to 1X does it at first for weight or aero,” says Rapp. “But they stick with it because it’s simpler, and that just makes riding a bike more fun.”