Oval chainrings. We've come a long way since Biopace, but they haven't gone away. You can get a big variety of designs, with varying degrees of egg-ness and some with ramps and flat bits and all sorts. The absoluteBlack chainrings are a meticulously-CNCed perfect oval. We've had a few in for test, and I've been riding the narrow-wide version on a SRAM Force CX1 setup on my Kinesis Tripster ATR, which does a bit of on-road and a bit of off-road. And I have to say, I like it. It's staying on.
So, what's the benefit? Well, the oval chainring, according to absoluteBlack, gives a smoother and longer power transfer over the pedal stroke. Here's a graph to look at:
What's this showing? Well, in the top view you have the power application around the pedal stroke for the round ring, and at the bottom it's the oval ring. There are two particular things to note.
The first is that the power plots have a slightly longer and slightly flatter peak on the oval ring. There's not much in it, but that suggests you're able to apply the power in your pedal stroke for a bit longer.
The second is that in the pedalling monitor section on the right hand side, the forces applied to the cranks are slightly closer to perpendicular where they meet the circle. That means a bit more of the power is directly pushing the crank round and a bit less is pushing away from the ring.
Actually there's a third thing to note too: the absolute power in the two graphs is basically the same. An oval chainring won't make you a more powerful rider. It can, absoluteBlack says, make you a more efficient rider.
These chainrings are aimed at riders in the mid-ability levels who are interested in performance and don't have a very even pedal stroke. The more you practise your pedalling, and the more you even out your stroke, the less of a difference the ovality is likely to make. That's not to say that they're no use to a pro, because a quick scoot round the parking lot at a time trial stage of a big tour will throw up plenty of oval rings. There are lots of pros who swear by them, especially for time trials.
Does the science back that up? Well, there have been plenty of studies and some show an advantage, some don't. This one is possibly the most interesting, in that it uses a theoretical model rather than real-world rider data, and suggests there should be an advantage.
"The optimization identified a consistent non-circular chainring shape at pedaling rates of 60, 90 and 120 rpm with an average eccentricity of 1.29 that increased crank power by an average of 2.9% compared to a conventional circular chainring", says the abstract. That level of eccentricity is pretty much the same as the absoluteBlack rings.
I'd certainly put myself in the mid-ability bracket, assuming it's a reasonably generous one. I'm a third cat racer and fairly fit, but it's not like I'm bashing out 30 hours a week on a Wattbike trying to perfect my sausage. Apologies if you don't know what that means. Anyway, I fitted our 40T SRAM narrow-wide chainring to my Kinesis, which is fitted with biggish tyres and mostly spends its life in the back lanes with the occasional off-road foray thrown in. (You can get a 42-tooth ring for the same money, or a 38 or 36T for £54.99.)
The first thing you notice when you set off on the oval ring is that it feels a bit odd, but not as odd as you expected it to feel. There's a slightly wobbly few pedal strokes but really it doesn't take much getting used to. For most of the time I was riding the chainring I didn't pay it much attention. That was helped by the fact that it's near-silent in operation; 1X setups are quiet anyway, but this ring is even quieter than the round SRAM one.
Here's where I did notice it. Firstly, on steeper climbs it does seem to give you a smoother pedal stroke. That's true either in or out of the saddle, but for me it was most noticeable when standing. Either way, though, it does seem a bit kinder on your knees. I have a slightly problematic right knee and pushing up the steep stuff later in a long ride is where I start to feel it. It seemed to me that the knee was better behaved on the absoluteBlack ring than on a round one. That may be a bit apocryphal as it's an issue that comes and goes, but it tallies with what other people have said about the rings.
Secondly, the oval ring seems to offer slightly better traction over the loose stuff, either on gravelly bits of road or on genuine off-road sections. If you have a slightly flatter, slightly longer power application on the pedals then you could argue that's what you'd expect. Again, we're talking marginal differences here, but I preferred the feel of the oval ring on more technical climbs.
What I didn't find was that the oval ring allowed me to climb two gears higher than normal, nor did it knock 5 minutes off my time up a 45-minute climb. Not that we have any 45-minute climbs round here. Those are examples of feedback on the absoluteBlack website and I genuinely don't think gains of that magnitude can be attributed to the switching of a chainring. I can't see how it would ever make that much of a difference.
Other people reported that it helped with lower back issues. I have some of those, like every 40-something man in the whole wide world, and I didn't really see a change in fortune from switching to an oval ring. It may be that it helps with lower back pain brought on by specific musculo-skeletal issues that I don't have. It's hard to say.
To further explore the gains or lack of, it's worth adding in road.cc tech editor Mat's comments on the rings. He's been using the road rings, set up on a Dura-Ace chainset, and he reports that they don't really do anything for him. It's worth pointing out that mid-ability bracket would have to be generous in the opposite direction to include Mat (a 70.3 Ironman UK age group champion), and given that he pedals everywhere at about 100rpm it's clear he's spent a lot of time getting his pedal stroke just so. Maybe he's above the top end of where it'll really make a difference.
Did it make a difference to me? Yes. Not a big one, but a discernible one. The most telling question with any product like this is, of course: will it stay on the bike now that the testing period is over? And the answer in this particular instance, for me, is yes. I prefer the oval ring to the round one that it replaced, and I can see a small benefit from it. Personally I'm not a big fan of the spidery CNCed look, but I'll live with that.
Oval tech smooths out your pedal stroke (a bit) for a helping hand on the climbs
road.cc test report
Make and model: absoluteBlack SRAM 1x narrow-wide chainring
Size tested: 40T
Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
Why our oval chainrings work
Our Oval chainrings work because a rider does not produce power evenly through a pedal stroke; they maximize the part of the stroke where power is produced and minimize resistance where it isn't. Oval rings make the spin cycle a lot smoother and are easier on legs while climbing. Believe it (or not), but a round chainring doesn't transfer torque to your rear wheel as smoothly as an Oval one. You will actually feel your stroke to be more "round" with an Oval shape than with a round chainring.
Why it matters
Traction, Traction and Traction. With oval rings rear tire traction improves greatly on loose and slippery terrain. Smoother power delivery to your rear wheel means that you will be able to maintain better, constant cadence; get less stress on the joints (knees) and therefore be able to keep certain level of effort for longer. This results in higher average speed. Moreover, 11 studies made by various Universities in the World show that using oval chainrings human legs utilize more muscle groups (compared to round one), but each of them to lesser degree. Load from pedaling an oval chainring is spread over greater muscle mass which in effect gives you the feeling of fresher and more relaxed legs. It is world's finest oval chainring backed by tens of thousands of customers.
Very nicely CNCed.
I found it a positive experience, especially on rougher climbs and steeper roads. It hasn't transformed my riding but it does do something.
Wearing very well; anodising is coming off the teeth but no real wear.
About the same as the round ring it replaced.
I think it's a personal thing – if it works for you then it's a good investment.
Tell us how the product performed overall when used for its designed purpose
It did make a discernible difference, but there aren't huge gains to be made and it depends on your form on the bike to a large extent.
Tell us what you particularly liked about the product
Felt good on steeper road and rougher cyclo-cross climbs.
Tell us what you particularly disliked about the product
Not sure about the looks but that's a personal thing.
Did you enjoy using the product? Yes
Would you consider buying the product? Yes
Would you recommend the product to a friend? Yes
Use this box to explain your score
Hard to score. The gains to be had are marginal but I did find the experience a positive one and the chainring is still on the bike. Not everyone will get a benefit, or the same benefit.
About the tester
I usually ride: whatever I'm testing... My best bike is: Kinesis Tripster ATR, Kinesis Aithein
I've been riding for: Over 20 years I ride: Every day I would class myself as: Experienced
I regularly do the following types of riding: road racing, time trialling, cyclo-cross, commuting, club rides, sportives, general fitness riding, fixed/singlespeed, mountain biking, Mountain Bike Bog Snorkelling, track
Dave is a founding father of road.cc and responsible for kicking the server when it breaks. In a previous life he was a graphic designer but he's also a three-time Mountain Bike Bog Snorkelling world champion, and remains unbeaten through the bog. Dave rides all sorts of bikes but tends to prefer metal ones. He's getting old is why.