With way too much time on my hands now I find it impossible to not work on my bike. It is a brand new Lynskey R300 so not much needs to be done. The chain has been cleaned and paraffined. Everything adjusted and cleaned.
I enjoy reading about bike riding as well and came across oval chainrings. Read the many reviews from Absoluteblack and decided that it may be worth trying. Anything that might help these 67 year old legs on 50-60 mile rides and steep hills is worth a shot! With few exceptions, the consensus is that they help or at least don’t hurt.
Not wanting to spend $90 on a whim, I found an Absoluteblack 42t 110/5 chainring to replace the same SRAM on the Force 1x crankset on eBay for $35 shipped to the house. Used, but like brand new. Instructions online seemed less that clear, but the chat box that opened on their website was answered immediately and clarified any issues.
Here is a photo of it installed. Looks good and I like that it does not look oval when not turning. No chance to ride it yet. Crappy rainy cold weather. Will keep you updated.

i use oval rings got on line Doval brand cheap seem to work well. i think i saw improvement
good luck

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what's old is new.

https://www.sheldonbrown.com/biopace.html

You might like it. I tried an old set of Biopace 52/42 chainrings on a road bike last year. It helped with my choppy pedaling style. Due to various injures affecting my back and hips my cadence had become stompy.

The smaller Biopace rings are more eccentric and seem to offer a bit of leverage for folks who mostly mash down rather than spinning smoothly. The big Biopace rings are more nearly circular, less eccentric, and feel a bit better to me when spinning as smoothly as I can manage.

I've tried using only the small 42 ring on flat terrain in a smaller rear cog for cruising but it feels less smooth, a bit herky jerky. Works best for me for climbing.

And both Biopace rings feel best to me with shorter cranks. I tried 'em with both 170 and 172.5 cranks. The slightly longer cranks strained my knees just a bit. Switching back to 170 fixed that problem.

I also tried re-orienting the Biopace rings away from the factory preset, based on tips from various users. I tried it for awhile but switched back to the original orientation.

And I do single leg drills on the indoor trainer as part of my injury-recovery physical therapy to smooth out my choppy cadence and strengthen the upper legs and adductor muscles.

I didn't go into much detail as to why I chose Absolute black chainrings in my initial post. I know oval chainrings have been around for a long, long time, even well before Shimano Biopace rings. The current generation of oval rings, by various manufacturers such as Rotor, Wolf, Osymetric, as well as Absoluteblack, have evaluated the degree of "ovalness" and the timing and amount of the change during the crank arm rotation.

It seems from my reading that Absoluteblack had done some significant research before developing the shape and timing of the rings and it varies by ring size. Believe me, I am not trying to be an advocate for Absoluteblack or a fanboy. With the crap weather we have been having in New England since installing the ring, I have not been able (wanting) to ride. Low 40 s F with occasional snow flurries is not my thing. So at this point, I can have no subjective or objective evaluation.

As I said in my initial post, I chose Absoluteblack for the research and reviews I read online and because they look most like "normal" chainrings and don't upset my sense of aesthetics. Will update, either positive or negative, as the miles accrue. I don't have much invested in this experiment. Can, and will, switch back to the SRAM 42t ring if there is a negative impact. Will keep if I feel a positive change (obviously) or no difference.

My '84 Nishiki International came with them, although I replaced the small one with a smaller round one. I absolutely don;t notice any difference between the oval ring and the rouond ones on my other bikes, or even between the big oval and the small ring next to it.

It seems like a good idea in theory...and it may work as intended...I just don't notice it.

Happy Easter or Passover to all!

Just finished a 20.2 mile ride and thought I would share my experiences, It is a route I have ridden many times. Flat for most of it with gradual inclines or declines. Two killer hill areas.

Objectively: 0.57 mph faster! (just kidding, I have absolutely no objective data!!)

Subjectively:
1. From the very first pedal stroke, I felt no difference riding an oval v round chainring. No odd sensation. Nothing to get used to. Mind you this is a 42t ring which may play a part.
2. Riding on flat surfaces I felt no faster or slower. No sense my legs felt better or worse.
3. HIlls were significantly different. The last two miles of my ride has two hilly sections. The first is a 1/2 mile 9-11* grade. I am usually in my lowest gear 42 x 42 and sucking wind at the top. Today was in the second lowest gear 36 x 42. I did not do this intentionally, I just shift when I feel the need. I was surprised when I reached the top that I felt much better and it was only then when I looked down did I realize I was not in the lowest gear. The last hill is a killer that is almost a mile long with a center section that reaches 13*. Again, I felt much better at the top although on this hill I did shift into 42 x 42.

Way to early for an final conclusions, but a very promising start.

Same impressions I've had with the old Biopace rings. I mostly notice the difference on climbs at slower cadence. And into stiff headwinds. I had both Sunday, a 5 mile roller coaster climb into a 20 mph headwind, and a 2 mile gradual climb into a slightly less stiff headwind, maybe 15 mph by then.

My steel frame '89 Ironman came with the original 52/42 conventional round chainrings and 7-speed 13-24 freewheel. After a few rides in 2017 I realized I'd need to swap the gearing around to suit myself. I finally settled on a 50/39 round chainring and 13-25 freewheel combo, that I rode happily for a couple of years.

Then last year a '93 Trek 5900 (carbon fiber) bike I bought from a friend was fitted with 52/42 Biopace, taken off another Centurion Ironman (the Shimano group Ironman models had Biopace, while the Suntour equipped Ironman models came with conventional round rings). I'd been wanting to try Biopace. I did swap around wheels between 13-25 freewheel, and 13-28 freewheel and cassette wheels. The 13-28 suited me.

After stripping the Trek frame for an overhaul recently I moved the Biopace rings and crank over to the Ironman. I figured I wouldn't be able to handle the 52/42 chainrings on the heavier steel bike. Nope. Rides just fine. There's something about the eccentric Biopace rings that seem to offer a bit of leverage, but for me it works best at slower cadence and harder gears (smaller cog).

After I finish overhauling the Trek the Biopace rings and crank will go back on it. It'll be interesting to see if I can handle the old 52/42 round chainrings on the Ironman again. If not, that'll be a reasonable indicator that the eccentric smaller ring does offer a little mechanical advantage -- at least with my choppy, stompy pedaling style.

Stop comparing biopace to absolutblack. They're both oval but not in the same orientation.

They're more opposites than they are equivalent.

Most eccentric chainrings can be re-oriented. Even with only five bolt holes the Biopace can be reoriented to approximate the orientation of elliptical chainrings that choose a different default setting.

It's all very subjective and individual. Some folks say Biopace works better re-oriented from the default setting. Others argue over the differences in dwell time over the camming action provided by "flattened ovals" or "rounded rectangles" like the Biopace and Osymetric, vs the more conventionally oval shapes. There's no consensus because it's all complicated by individual physiology and subjective experiences, including some placebo effect.

Not worth nitpicking over, unless you're in marketing fighting over a nearly non-existent consumer base.

I finished a 33 mile ride yesterday. Thought I would give you my final review. Unless something drastic happens, I won't post further since everythng is consistent with my previous results.
Very clear to me that these rings help with steep hill climbing. Having much experience with my bike route, I find that I am faster and less tired at the top. Some hills in less low gears. I don't seem to see much difference on the flats, but the Garmin shows my overall speed to be about 1 mph faster. Could be strictly incidental finding.
Riding with an oval ring feels absolutely no different than riding with a round ring. Nothing to get used to.
I would place using an oval chainrings the same way that I look at any other upgrade to my bike. Last year I upgraded my wheels to Mavic Kysrium Carbon with tubeless tires. Definitely an improvement over the original alloy wheels but nothing outstanding. For $90 (if you payed full list price) it is a bargain compared to a carbon wheelset. For the $35 I paid it is a no brainer.
YMMV

I’ve been very happy with an Absolute Black ring on my mountain bike. I was pretty sure I felt an improvement but I’m not one to Strava or time my rides in any way. If I feel like going hard I do ( which is most often ) but if I don’t feel good I take it easy and don’t need a readout of my ride later to make me feel bad about it.

Anyhow, I had a bottom bracket issue so I had to return to a round ring and that’s when I really noticed it. I missed the oval ring a lot, felt slower climbing and more tired after. After this post I’m now thinking why didn’t it occur to me to put them on my road bike? I guess this will be added to my things to do list......

Biopace is not a valid comparison & with 5 bolts in the pattern you can not rotate the ring the essentially 90 degree difference to make a modern equivalent. For that matter, ovals & squares are not the same shape.

Biopace was designed to keep foot speed constant by dwelling on the dead spot in the stroke. The logic was a constant foot speed would make for a less tiring experience. AbsoluteBlack, Rotor, et al, rushes past the dead spot minimizing the time in the dead spot to maximize the time in the power part of the pedal stroke. This recruits more muscles by spreading the load more evenly among more muscle groups. The result: Less tired individual muscles & less cramping of those tired muscles.

Does it work? Absolutely.
On standard round rings.
With Oval rings,
Same average power, same heart rate. Same time. Same everything. But the "how you get there" is different. On a Qubo Elite fluid trainer the rear wheel was 5% faster all things being equal.

...Also it's easier to hold a higher cadence with oval in my experience. I now run Rotor & Absolute black on 3 of my 5 bikes. Those 3? The race/tt bike, the touring bike, and the long distance all-rounder. The mountain bike & the vintage bike are in the queue.

I'd be curious to see others back to back A/B comparisons. I, myself am only a single data point.

Enjoy.

My fatbike was between stalling and slipping in the different parts of the stroke in deep snow or slippery conditions. Oval chainring improved that by smoothing out the torque to the wheel. I really like it. It also spins well.

I also added oval to my hybrid. It just seems to work better uphill and spinning. I couldn't tell that I'm I'm faster, just seems better.

Both have AB rings. Some other oval rings seem less ovalized, but I never tried one. When installing oval, I also went to fewer teeth, so I can't corroborate claims of more power.

Of course someone had to bring up Biopace. Hey, I tried a 3-gear derailleur from 1936 and it wasn't perfect. Therefore I conclude 12 speed XT doesn't work well.