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Extend the sweet spot.
While it hasn't yet found a competitive home outside of crits and triathlon, one-by technology has certainly proven its worth in those two disciplines. Rotor's QX1 Aero Road Chainring ushers the nascent technology into the land of ovalized chainrings, netting claimed gains in efficiency for the one-by set. Despite its signature shape, the oval ring maintains chain tension throughout the pedal stroke and plays nicely with clutch rear derailleurs.
The one-by version is also more ovalized than the standard (Dare we call it "traditional"? No, no we daren't.) Rotor ring, bumping up to 12.5% instead of the original 10%. That makes the sweet spot of the pedal stroke that much sweeter, letting you linger in the degrees where you're putting the most power into the bottom bracket.
- A one-by chainring for any skinny tire application
- 12.5% ovalized profile extends the pedal stroke's sweet spot
- Aerodynamic face helps reduce drag in one-by setups
- Tooth profile retains chains even on rough country roads
- Maintains chain tension throughout pedal stroke
- Compatible with clutch-equipped rear derailleurs
- Item #RTR001E
- Q & A
Excellent oval 1x chainring!!!
- Familiarity: I've used it once or twice and have initial impressions
I purchased a 52t Rotor QX1 Aero 1x chainring from Competitive Cyclist. It was a "backorder" item because they didn't stock the 52t size (the largest) and they quoted two week to delivery. It actually arrived in about half that time. My thanks to Competitive Cyclist!
I'm using the chainring with a compact (110 bcd) SRAM Red 22 crank. I converted it to 1x a couple of years ago on my composite road bike because I never used the small chainring. I was using a 50t SRAM X-Sync 1x chainring and it worked good, but I never liked the "clean-out" feature of the teeth. You see, the X-Sync was designed for muddy cyclocross racing and the wide teeth have an extra bulge in their side to help clean mud and debris out of the chain. The problem with this tooth design for a clean road application like mine: it unnecessarily increases friction since the chain plates must contact and slide over this side bulge.
So I had two reasons to look for a new 1x chainring: (1) I wanted one with smooth teeth. And (2) I wanted a larger chainring so I wouldn't have to spend so much time on my 11 or 12t cassette cog. This would enable me to spend more time with the chain closer to the center of my driveline, again reducing friction. Getting an oval chainring was a bonus -- I'd wanted to try one for years and, when I saw that Rotor made one that would work with my SRAM Red crank, I was delighted.
About my SRAM Red crank, it has a five-spoke spider to which the chainring attaches. However, the drive-side crank arm doubles as one of the five spokes and uses a hidden reverse-mounted bolt. This means that the chainring must be precisely 4.0 mm thick so it will correctly fit the space between the four outward-facing mounting surfaces of the normal spokes and the one inward-facing mounting surface behind the crank arm. I'm pleased to report the oval Rotor QX1 Aero chainring does perfectly, making it one of the few 1x chainrings (apart from the SRAM X-Sync) that will fit a Red crank.
As a "rule of thumb", Rotor says that the wide part of the oval is the equivalent to the actual tooth count plus two. And the narrow part of the oval is the equivalent to the actual tooth count minus two. This means that my 52t oval chainring effectively acts like a 54t chainring when I'm pulling the most chain through the most powerful downward portion of my pedal stroke. And it acts like a 50t chainring when I'm pulling the least chain through the weakest portion of my pedal stroke across the top and bottom.
However, it's my understand that this "thumb rule" is based on a 10% oval and this QX1 Aero chainring actually has a slightly more aggressive 12.5% oval. So, I guess the the effect would be a little greater.
As for how this chainring "feels". Honestly, I'm surprised how little difference I actually feel. My first two rides (25 miles each for a 50 mile total) seemed perfectly "normal" except I could tell that I was working with a larger chainring. But after the first 25-mile ride (which consisted of HIIT reps (high intensity interval training), I immediately felt like different portions of my legs were sore. It was as if I had been using my leg muscles differently and they were letting me know. After a good stretch and one rest day, I did my next 25-mile HIIT session and noticed no unusual soreness at all. Evidently, my legs has adapted after just the first session.
As for power, my average and work-reflected (WR) power for the first workout were normal (within 1 watt of the same workout on my previous round 50t chainring). But on my second workout (after my legs had adapted), my power was 14 watts higher. Since I'm just starting to use my first-ever oval chainring, I'm not going to draw any conclusions yet. But it would be nice to see that the power increase is real and due to the oval chainring. But, even if it is for me, I wouldn't expect it to be the same for everyone else because oval chainrings don't appear to help all cyclists. I guess it depends on how you pedal.