Oval Chainrings

[MichaelW2]

Everyone agrees that oval rings are the best thing since dogs bollx but no one can agree on which way the axis should be phased with respect to the crank.

 

[Racing roadkill]

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.

And the fact that chains really didn't like them.

 

[Dec66]

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.

I'm not on about John Q. Citizen, though, I'm on about a marginal gain for the top lads.

My Cube is a triple on which I can go 30/32 should I choose; indeed, part of the reason I got it was that gearing, for when I take on some of the 1 in 5's and 1 in 4's round here.

In practice, however, I find I'd rather turn 30/23 or 30/25 on those hills and stand up, partly because I feel like I'm going to fall backwards if I remain seated and partly because I don't like the sensation of spinning away with little forward momentum.

What I'm really on about, with the ovoid ring, is that one *may* get a marginal power gain up long, steep hills, turning something like 36/25, if you have sufficient power to weight ratio to exploit it; a sort of "cam" effect.

For the average bod, as you say, it's pointless; I'm just wonder if it's pointless for absolutely everyone. I can't see it just being a gimmick, which pros use because they get paid for it, as something intended to provide a marginal gain can just as easily provide a marginal loss.

To give a non-cycling example which our resident owl arses may remember; Alan Ball was paid by Hummel in the early 1970's, which he described years later as being "bloody rubbish". So poor, in fact, he resorted to having Adidas boot painted white and using those instead.

 

[Yellow Saddle]

I'm not on about John Q. Citizen, though, I'm on about a marginal gain for the top lads.

My Cube is a triple on which I can go 30/32 should I choose; indeed, part of the reason I got it was that gearing, for when I take on some of the 1 in 5's and 1 in 4's round here.

In practice, however, I find I'd rather turn 30/23 or 30/25 on those hills and stand up, partly because I feel like I'm going to fall backwards if I remain seated and partly because I don't like the sensation of spinning away with little forward momentum.

What I'm really on about, with the ovoid ring, is that one *may* get a marginal power gain up long, steep hills, turning something like 36/25, if you have sufficient power to weight ratio to exploit it; a sort of "cam" effect.

For the average bod, as you say, it's pointless; I'm just wonder if it's pointless for absolutely everyone. I can't see it just being a gimmick, which pros use because they get paid for it, as something intended to provide a marginal gain can just as easily provide a marginal loss.

To give a non-cycling example which our resident owl arses may remember; Alan Ball was paid by Hummel in the early 1970's, which he described years later as being "bloody rubbish". So poor, in fact, he resorted to having Adidas boot painted white and using those instead.

Power is work done over time. Since the crank itself can do no work and not shorten the time, it cannot produce power and cannot give you a power gain.

This is the bicycle equivalent of the perpetual motion machine. It is amusing but nothing more.

 

[Dec66]

Power is work done over time. Since the crank itself can do no work and not shorten the time, it cannot produce power and cannot give you a power gain.

This is the bicycle equivalent of the perpetual motion machine. It is amusing but nothing more.

OK, fair enough.

I do recall the OP asking a while back for some panacea to help his climbing; safe to say, this isn't it. It's back to hard graft and diet, @rugby bloke (I feel your pain, quite literally).

 

[Yellow Saddle]

OK, fair enough.

I do recall the OP asking a while back for some panacea to help his climbing; safe to say, this isn't it. It's back to hard graft and diet, @rugby bloke (I feel your pain, quite literally).

Unfortunately the answers to these things are as simple as hard graft and diet, as you righfully note. Genes also help a little bit as does HTFU.

 

[Tim Hall]

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?

Sheldon (Brown not Cooper) claimed some success when using Biopace on a fixed wheel, although John Allen, his successor, wasn't so keen:

People are often astonished to learn that I ride Biopace chainrings on fixed-gear bikes. They imagine that there will be tremendous changes in chain slack as the chainring rotates. In practice, this is not the case. A 42 tooth chainring will generally engage 21 teeth against 21 chain rollers, regardless of its shape.

There is a slight variation in tension resulting from the varying angle between the two straight runs of chain as the axis of the chainring rotates, but this has not generally been of a sufficient magnitude to cause any problem in practice for me.

[I've tried this too, but I'm not as happy with the change in tension. The sprocket is smaller than the chainring, so the chain doesn't meet the chainring at two points precisely opposite one another -- John Allen.]

 

[betty swollocks]

I had a correctly orientated oval inner chainring on a Mavic chainset years ago.
I liked it. I'm not sure it made climbing faster, but It did make climbing easier especially on sustained climbs. When it wore out, Mavic didn't make them any more.
I've since used a custom-made chainring from Eggrings on my Rohloff-equipped bike, without a chain tensioner and enjoyed the experience.
So, yes, they can be used on non-derailleur transmissions successfully and without the chain derailing, provided the ovality is not too extreme.
On my new custom-made bike (it's being built at the moment) I have specified a Sram 1x11 with a compatible Absoluteblack oval chainring.
I did ride Biopace when they first came out and they were horrible, because, as others have said, the orientation of the ovality was wrong.
That's my two penn'orth.

 

[sidevalve]

Your money = your choice. Me ? I'd put the cash to a nice new bike fund.