Absolute Black Oval Chain Rings
There are a few pieces of bike stuff common across my fleet of bicycles. Those are a helmet, clipless pedals, and oval chainrings. Today I'll be writing about my experience with oval chainrings.
Specifically oval chainrings from Absolute Black (AB) and here is their website, https://absoluteblack.cc/. I first tried an oval chainring on my custom Ellsworth Rogue 60 as the oval chainrings were becoming popular around Tucson and I wanted to give it a try. Even more so when I learned they had a variety of colors, sizes, and were compatible with just about every crankset on the market.
The Tech Behind the Oval
The big idea behind oval chainrings is they provide a large chainring on the pedal downstroke (the power zone) and a smaller chainring on the "horizontal" pedal stroke (weakest power zone) optimizing your power output. Absolute Black calls this "Ovality" or the measure of oval-ness. Their chainrings range from 10.2% to 14.4% ovality. Returning to my first explanation, "32T oval ring will suit best someone who uses 31 or 32T chainring currently. While pedaling, you will feel similar effort to the one riding round 31T ring, but you will gain the speed similar to riding 34T chainring" (Absolute Black size guide).
AB oval chainrings are available for just about every crankset in existence which means anybody can add one to their bike. These chainrings are beautifully cnc'd out of aluminum and can be anodized into just about any color you like. The chainrings are also light as there is no excess material left giving you a very light and flashy chainring. An AB 32 tooth oval chainring (34t equivalent) weighs 59 grams, vs the common SRAM 32 tooth round chainring weighing in at 78 grams (note, a cliff bar weighs 68 grams). The AB chainring costs ~$84 while the conventional SRAM has an MSRP of $107 (didn't expect the AB to be cheaper!!!).
First Impressions
I noticed the difference between the oval chainring and the circular chainring on my first ride. It was a nice and easy cross country ride and we were just cruising, not challenged by the terrain. I thought I was experiencing pedal bob at first and I was very unhappy, because the demo bike didn't exhibit pedal bob... At some point I decided to look down at the turning cranks (it was that easy of a trail) and noticed the suspension wasn't bobbing and the "pedal bob" feeling corresponded with the tallest section of the oval! This put me in a better mood and I concentrated on the feeling of the ride.
Over the coming weeks I found my average cadence (pedal speed) decreased. It was more comfortable to pedal at slower speeds with the oval while feeling less strain on my knees, which is wonderful for my old legs. I feel like the slower pedal cadence allows me to save energy over the conventional round chainring. This agrees with AB's claims of increased pedaling efficiency over conventional round chainrings. Note, AB claims a small improvement in efficiency on the order of ~5nm per pedal stroke (https://absoluteblack.cc/why-oval/) meaning this will not be a huge difference, but adds up as the ride gets longer.
Due to the oval chainring's shape, it hangs down lower off the bike than the conventional round chainring. No duh, right? This doesn't matter in cross country riding but comes a factor when riding downhill and enduro. The 36t oval chainring on my Ellsworth Rogue 60 was so large that it eclipsed the bash guard rendering it useless, so I took off the bash guard. The AB chainring is lighter than the conventional stock chainring and isn't nearly as tough. I have bent quite a few AB chainrings going over obstacles where the chainring struck the ground/obstacle. I don't think this would have happened with the conventional-heavier chainring. Such is the price with lightweight. However, I must mention that I never dropped a chain from a bent chainring, it just looked ugly, and I had great luck removing the bend in my garage with a vice and a wrench.
Conclusion
The AB oval chainring adds bling to your bike, slightly reduces weight, and saves a couple bucks over the conventional SRAM round chainring (at the cost of durability). One will experience slightly more efficiency on an oval chainring vs a round chainring, but not an Earth-shattering amount.
This is a niche upgrade for the cyclist that wants more efficiency, bling, and weight reduction. Not every rider will notice or appreciate the oval chainring. I recommend trying someone else's bike with the oval before you buy one, or wait until your round chainring is worn out.
My personal fleet with oval chainrings
References
4. http://tucsonbicycleservice.com/
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