Volumes have been written about turning the perfect circle. Some say that it takes a lifetime of cycling before one can truly master the act of transferring leg power smoothly into 360 degrees of uninterrupted torque – which begs the question: “If pedaling circles is so damn hard to learn, have we been doing it wrong all these years?” The oval chainring makes a good argument that there is, indeed, an easier way to pedal efficiently.
When SRAM slayed the mechanical monkey that used to cling to the seat tube near the bottom bracket, they also eliminated the need for round chainrings. The absolute precision that a front derailleur requires to shift reliably dictates the use of round sprockets. SRAM’s victory over the front mech and its introduction of the X-Sync tooth profile cleared the way for mass production and the potential acceptance of oval, and asymmetric chainrings. Paradoxically, SRAM largely ignored that potential market until well after the release of their 12-speed Eagle ensemble. I’ll let SRAM tell the story:
Tech Notes X-Sync 2 Oval Details:
• Construction: Forged, machined aluminum with Eagle X-Sync 2 tooth profile
• Direct-mount only, cross-compatible with GXP-type cranks
• Sizes: 32, 34, 36 and 38-tooth
• Offsets: 3mm or 6mm (Boost and non-Boost)
• Colors: Black anodize only
• MSRP: $119 USD
• Contact: SRAM
SRAM’s Eagle XX1 chainrings are beautifully made, and the new oval versions uphold that standard, with machined reinforcement webs, laser etching, and the trademark scimitar tooth profile, which create a more seamless release and engagement when the chain is feeding into the sprocket from the extreme ends of the 12-speed cassette.
The ovality (a relatively new word to cycling) of the 32-tooth chainring is roughly 12 percent which, in my experience, is a near perfect balance for delivering more consistent torque to the rear wheel, while retaining the option to spin a wider range of rpm than some asymmetric chainrings encourage.
Paired, narrow-wide chainring teeth have nearly eliminated accidental chain derails, and arguably, oval chainrings would not be gaining popularity among mountain bikers if that technology did not exist. SRAM’s X-Sync 2 chainrings use their next-gen tooth profile in addition to narrow-wide, and Sync 2’s taller teeth may play a positive role, further preventing a derail as the gyrating chain feeds onto the flatter side of the oval chainring.Trail Report
Anyone who has installed a SRAM direct mount chainring will vouch for how simple the task is. An 8mm Allen removes the crankset, and the chainring pops off after removing three screws with a T25 Torx bit. The crank’s spline prevents the oval chainring from being improperly indexed so, reverse the steps, torque the screws and, boom, you are ready to ride.
I am used to oval chainrings, but bike testing requires me to switch back and forth from round to oval, often on the same day, so there is always a brief period when my legs are acclimating to the different sensation. I was encouraged by how natural the X-Sync 2 Oval felt from the outset, and by how quiet the SRAM chainring was. All fresh chainrings make noise initially as the sharp edges and fresh anodizing meshes with the chain various angles. Most new sprockets buzz for at least one ride, oval rings usually take twice as long to bed in. The SRAM chainring was silent running within the first half hour on the trail and stayed that way to date. Remarkable, especially because oval rings usually project a subtle pulsing sound.
Big claims have been put forth in support of (and arguing against) oval chainrings. I’ll refrain from fanning that fire. What I can tell you from back to back rides on the same bike using SRAM Eagle round and oval sprockets, is that anytime traction is lacking, or when climbing requires maximum efforts over uneven terrain, the oval chainring is the clear winner. Heart rates are lower and the legs tend to roll through the crank-circle in situations where they would most often stall powering a round ring.
Overall, pedaling with the X-Sync 2 Oval makes it more comfortable to push a taller gear, topping rolling climbs where I would be reaching for a downshift. At speed, or when the trail is flowy, if there are advantages between the two, they are negligible. The most apparent benefits, the ones first timers will reap, are a lot more traction and stronger, more fluid technical climbing.Pinkbike's Take: