Is there anything to Oval Chainrings?

[Singleton]

My poking at the matter has proven a lot of contradictory information on everything from installation to effectiveness to it even being a scam. Given my perennial limited funds I'd rather fish for information from a group of bashers than just throw money at the situation.

 

[MattiThundrrr]

It is funny. The old ones were supposedly deadly for knees, it's why they went away. I don't understand why they came back. I avoid them but have no evidence to justify why, just the advice of a road rider I knew thirty years ago

 

[Captain Awesome]

Are you going for Max watts, efficiency, or what? What bike?

I run oval now on my gravel bike and it's great for cadence work. Unless you get one that's oriented correctly though to put the power in the power zone which is just below crank level it's all a waste. Much like biopace rings which were not oriented correctly so they never optimized power

 

[Captain Awesome]

It is funny. The old ones were supposedly deadly for knees, it's why they went away. I don't understand why they came back. I avoid them but have no evidence to justify why, just the advice of a road rider I knew thirty years ago

It's all about how the oval is "clocked"

Put it in the wrong place and it's either a dead zone or it's going to be killer on your knees. Put it in the sweet spot and your cadence will actually feel more circular than with a round chain ring. It's hard to explain it's more of a feel

 

[MattiThundrrr]

I knew the new breed was "clocked" differently, but wasn't sure to what end. The gravel kids are raving about them. Thanx Cap

 

[Oldbiscuit]

I ran one on my road bike back in the 80’s and I swore by it.

 

[Singleton]

Are you going for Max watts, efficiency, or what? What bike?

Basically try getting just that little bit more power than I'd get on a ring size i'm comfortable with since 'well it can't hurt so long as i get the orientation right, right?' As for the bike? The one from my intro, it's the only bike I have so 'yea yea it's not road or even particularly efficient since it's essentially framed up to encourage the user to sit rather than stand or lean forward.' I don't like taking up a lot of space in my stepdad's garage along with generally not a lot of discretionary income. So I can't go n+1. I have to go n=1 in spite of having space enough to have a nice fleet (especially if i went for the trash pick route but good luck getting transport and help on that front.)

Mostly it's a case of 'looking for anything that makes hills less of a wall.'

 

[Captain Awesome]

https://absoluteblack.cc/why-oval/

 

[AndyA]

Mostly it's a case of 'looking for anything that makes hills less of a wall.'

As Captain Awesome points out, an ergonometrically proper oval chainring can help with cadence, but I don't believe that it would do much to flatten hills. You need to get your gear ratios right (and get your legs stronger) for best performance on hills. Have fun!

 

[gowjobs]

If you have really good cadence, oval chainrings won't be as useful. If you're an old BMX'er like me, who has a discernible power stroke resulting in an uneven cadence, this will help round that out and smooth your power delivery. I have an oval on my (distance rider) gravel bike, and a round one on my vintage mountain bike that sees mainly trail duty.

 

[ifitsfreeitsforme]

I had a mtb with them circa 1990, but it was at the end of the fad, and they were barely oval. I don't recall feeling anything different.

 

[us56456712]

About three years ago there was only one Tour de Farce rider who was using an oval. The only local folks I know who are currently using them are mountain bikers in their 70s or snow bikers around 60. They can’t get low enough gearing with the new 1x gear set ups and tried the oval. Didn’t help enough. For some reason their crank assembly wouldn’t take 26 tooth narrow wide rings.

 

[rickpaulos]

The Japanese engineer who designed the BioPace rings (late 1970s) published a paper with a bunch of charts and tables. I remember the main benefit of the Biopace shape was to reduce pressure on the knees at peak power by about 10%. A knee saving device for sure. The ring was designed so your feet speed up during the down stroke if installed properly. You really notice when you first start riding them for the first time. It feels a bit like something is slipping. But after a few minutes you don't even notice the effect. Shifting usually works okay even thought the distance from the derailleur cage and teeth vary. The Biopace isn't strictly oval, but it falls under the description of oval rings.

Biopace was copied (sort of) by Sugino or some other crank maker. I get lots of those at the local bike coop. Those are more common. I can supply those with the cranks.

Oval rings go back over 100 years. Some have extreme oval shapes, others barely noticeable. I've seen a tri-oval shaped (like a wankel engine rotor).

Another variant was the Houdaille PowerCam crank set. It used a cam installed on the side of the bottom bracket shell that was followed by a lever that would speed up or slow down the crank at certain points in the rotation. The cam came in different shapes so the power curve could be altered. the rings were round but the effect was the same as non-round rings. Scott Dickson used it well to win Paris Brest Brest several times. I rode his bike one time. You can't spin or even force it. But I felt comfortable pedaling a 54x12 gear at about 20 mph. Just odd. Sprinting wasn't even possible. The crank set was expensive. They sold whole bikes with them but the cranks cost so much the bike was very overpriced. who wanted to pay $400 for a $200 bike with at $200 crank on it with an unproven idea.

IMO, the Biopace shape had it right. Others do just the opposite which has to be really bad for your knees and blood pressure. I you want to be able to ride bikes for decades to come, protecting your knees is important. Higher rpms is better for you all around.

 

[rickpaulos]

BTW, if you want more power there are two main things. Pedals that lock your feet to the pedals. Instead of just pushing on flat pedals with your glutes, all the muscles in your legs can help out. When all the muscles work, the glutes don't have to work so hard. SPD or Looks can increase your speed by quite a bit with less effort. The other factor is training. The more you ride, the stronger you will get.

 

[Karate Chicken Industries]

Saint Sheldon ran oval rings on his fixed gear bike.

I usually flip them when they land in my parts stash.

 

[Tallbikeman]

I never heard bad about oval chainrings and has been mentioned they have been around a long time. The idea boils down to speeding up your foot speed at the top and bottom of the pedal rotation. This part of your pedal stroke offers little power. Then the stroke slows down as you get into the bigger, further from crank axle, part of the oval gear. This has the effect of having more time producing usable power during your pedal stroke than a round chainring will produce. It is about more power. All the cautions about riding too high of a gear ratio pertain so that you don't hurt your knees. Several commenters have hit on this notion of regular cadence and part of that idea is that you don't push so hard that you hurt yourself. Training for road racing involves spinning the cranks at a fairly high rpm with a regular cadence. One of the myths about power is the need for shoes that clip into pedals and you get power on the the backstroke also. This idea has been tested extensively with some tests available on the internet as you tube videos. Basically the shoes and cleats only help during sprinting. The rest of the time you can use a platform pedal and regular shoes to get the same power numbers as clipped shoe performance.

 

[oldiron]

Back in 1989 I bought a new Schwinn High Sierra that had them, I didn't like them from day one. They were billed as being easier to ride for those with knee issues but I found the exact opposite. They came off the bike after only a few months.
I actually tried them again 20 years later and got the same results.
However, I know many who swear by Biopace rings and actively hunt for them.
They work in theory but I never liked how they felt. I kept getting told that you'll never notice them but they were wrong.

The first change I made to the High Sierra was to only put a round ring on the larger ring, that felt better but you had to be careful when shifting and it led to some ugly scarred up rings so both got changed out for round rings.
I still never liked the bike in general. The index shifters, shorter wheel base, combined with too aggressive OEM tires finally made me sell it.
(I put it back to 100% stock and sold it after less than a year). In that time Schwinn had recalled the frame due to issues with the black chrome. the replacement frame soon had the chrome peeling off, so it got a new frame again. A week after I got it back with the third frame I sold it and pretty much broke even in the end.

 

[Karate Chicken Industries]

However, I know many who swear by Biopace rings and actively hunt for them.

When I come up on some, would it be alright to drop you a message so I can sell them to those looking to buy a set?

 

[oldiron]

I list any I find on eBay, but all I had were always new. I don't know how well used one's would sell but there's definitely been a following for them NOS. Those who use them love them but for me they just didn't feel right.
I also had a road bike that came with them but I swapped them out day one.
A buddy grabbed them up and put them on his bike and swears by them to this day. He's running them on an 80's Peugeot.

I think there's just as many who buy them as a curiosity as there is who intend to use them on their daily ride.
The idea never died, Stronglight came out with an oval ring design about 12 years ago, and back then, various brands offered their own versions of the Biopace. The Shimano version was the lease drastic of all the designs.

 

[us56456712]