Oval Chainrings

[rugby bloke]

Just had an advert for oval chainrings by Absolute Black come up on my Facebook feed. Never heard of an oval chainring before and not too tempted to buy one at £82 a pop. The ad claims it would make climbing easier, so out of curiosity - any experience or thoughts ?

 

[sidevalve]

Have one on the Dawes. Is it better - not sure. Is it worse - no. Got the bro in law to try it and he couldn't detect any difference either way. My hill climbing may be easier and the knees don't hurt [but then they never did] but it's not a big deal. If you want to try one look on E Bay and give a second hand one a go but at £82 not a chance.

 

[Racing roadkill]

Just had an advert for oval chainrings by Absolute Black come up on my Facebook feed. Never heard of an oval chainring before and not too tempted to buy one at £82 a pop. The ad claims it would make climbing easier, so out of curiosity - any experience or thoughts ?

Nothing new here. Halfords even used them, back in the 1980's on their bikes, they called them "Bio-pace".

 

[sidevalve]

Mine is the 'bio pace' type - they were a shimano make but I still wouldn't bother unless [as mine did] the bike came with them.

 

[GuyBoden]

Are these the same as the new rebranded Osymetric chainrings, I think Wiggins used them on his TDF win (a Sky Marginal gain).

 

[rugby bloke]

The feedback on Facebook seemed to be that they were popular in the 90s then went out of fashion as people suffered from sore knees.

 

[Hugh Manatee]

The early Biopace rings were basically 90 degrees out of kilter. Popular in the very late 80s. My Wildcat MTB had rings that looked like they were sliced from rugby balls. My 1990 range topping Saracen had round rings. You saw the old oval rings on lower end bikes in the early 90s. I think Shimano were just using them up.

Like someone said, Wiggins and Froome use them as a marginal gain as when in the correct alignment they reduce the dead spot in pedalling when power put through the cranks is at its lowest. Or something.

 

[Fnaar]

Mrs Fnaar has biopace on an old (early 1990s) tourer she was given. I haven't ridden it, as the bike is too small for me, and she hardly ever cycles, so doesn't really care about the difference

 

[Yellow Saddle]

These things are re-invented every 20 years with the same nonsense claims each and every time. Like perpetual motion machines, their claims are all bogus. Any pro's using them are doing so because someone paid them to do so. If you pay me enough I'll also use them. If you pay me enough I'll even ride deep section carbon wheels with garish white lettering and lycra with someone else's name embrazoned on it.

 

[Dec66]

Would they help on climbs?

I'm no expert in biomechanics, but my gut feeling is that they would help on the steepest climbs, where you were standing up on the pedals, if the flattened parts of the ellipsis were at the same point as the cranks. The downward drive of the foot would push through more teeth on the sprocket than a conventional chain ring.

However, when seated, there would be two points on each revolution where turning the crank would cause fractionally more resistance in each revolution, and this might give rise to the sore knees.

Have I got this right? I'm sure there are cleverer people that me who could explain it.

 

[Yellow Saddle]

Would they help on climbs?

No.

I'm no expert in biomechanics, but my gut feeling is that they would help on the steepest climbs, where you were standing up on the pedals, if the flattened parts of the ellipsis were at the same point as the cranks. The downward drive of the foot would push through more teeth on the sprocket than a conventional chain ring.

However, when seated, there would be two points on each revolution where turning the crank would cause fractionally more resistance in each revolution, and this might give rise to the sore knees.

Have I got this right? I'm sure there are cleverer people that me who could explain it.

Most of us just shift down a lower gear when required. The oval chainring was an invention that went in search for a problem and can be post-rationalized in a dozen different ways. I also particularly like the resourcefulness in nomenclature. Oval became Biopace, Ossymetric and one or two others I've now forgotten.

 

[Hugh Manatee]

And they're rubbish on a fixed!

 

[Yellow Saddle]

And they're rubbish on a fixed!

I'm sure there's a way around that problem. Rubber chainstays anyone?

Edit: I'm sure I can do better than that.

Variable dimension polymeric elastomer chainstays(VDPE) anyone?

 

[Dec66]

Most of us just shift down a lower gear when required.

And what about when you're on the lowest, as you may well be on the steepest climb?

FWIW I think that for 99% of people they are a gimmick. Maybe there is a marginal gain, I dunno. I'm just wondering out loud what it is.

 

[Yellow Saddle]

And what about when you're on the lowest, as you may well be on the steepest climb?

FWIW I think that for 99% of people they are a gimmick. Maybe there is a marginal gain, I dunno. I'm just wondering out loud what it is.

I doubt that the lowest "gear" on the fat part of the oval chainring is any lower than what is commercially available on round chainrings. With 28 (front) and 32 (rear) available you are already spinning like mad. In fact, it is nay-impossible to stay upright at speeds generated with this gearing, so, how low do you wanna go.