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Oval chainring?


By p2tx8 - Posted on 24 September 2014

NB: Originally posted elsewhere on the Global Riders Network and appears via syndication.

http://absoluteblack.cc/oval-104bcd-chainring.html
Has anyone heard/used one of these ones? According to them you will have basically 2 chainrings in one?

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Not common but not unheard of in the roadie world - think Froome and a couple of others use them.

Never heard of them for mtb.

Here is an article about them

http://cyclingtips.com.au/2012/09/osymetric-gimm...

Edit - not so much about 2 chain rings, the theory is (I believe) that on the weakest part of the pedal stroke the chainring is effectively smaller.

Those promises sound too good to be true. I'm in!

Been around for the best part of 30 years that I am aware of. My first decent roadie had them and they were known then as Biopace, a Shimano product. Don't know if they were first to market or not.

Does it make a difference, I was never good enough to know.

Have a look at Rotor Q-rings. The website should explain the whole concept. Whilst similar to the old Bio-Pace, I believe rotor have changed the position of the elipse,theoritically changing the power transfer through the position of the dead spot in the pedal stroke. (terminology??) and also made it tunable to your preference.
I have one fitted to my project 29er SS as I heard good things about them on a single speed and though it worth a try. I will update on what I think once I have finished the build.

Old.

Not the narrow wide implementation tho.

When I started road racing in ~1990 Shimano had a Biopace oval chainring. Never took off then either.

Chris Froome etc started using a greatly exaggerated oval ring in TTs and hill stages in the tour last year.
All the testing says some riders show benefit, others none at all. So no magic bullet for everyone.

Came standard for a while on some '90s New Zealand brand mountain bikes. The riders I knew at the time swore by them but they never took off. Don't think any of them missed them though.

There are a number of 'ovalised' chain rings, but most do not provide a N/W option.

Absolute Black:-
The question is how were the Absolute Black rings designed? Are they a Biopace copy? They are a different shape to the Q-rings and the Osymetric. The MTB Q-rings have three positions for mounting so that you can adjust the effect, Blacks and Osymetric have one position. Q-rings (33 and 34t) do not need a chain tensioner if fitted to a single speed. (reviews:- http://www.i-mtb.com/absolute-black-chainrings-x... and http://waki-leaks.blogspot.com.au/2014/04/test-a... )

For some research into ovalised see http://www.noncircularchainring.be/ and http://www.jssm.org/abstresearch.php?id=jssm-13-... and http://www.darwin.cycling.org.au/?ID=42069) (I cannot vouch for the independance of these researchers as I do not know their background). The first state "Any reasonable non-circular chainwheel has about 50% chance of being better than the circular shape" Of course this depends on the meaning of 'reasonable', others find little difference. But two makes (Q-ring & Osymetric) appear to provide a little more power than round rings once you have adapted to them.

I've used Bio-pace and Q-rings (http://www.cart32hostingred.com/cgi-bin/cart32.e...). Bio-pace wasn't worth the effort. Q-rings (very diffrent to Bio-pace) I found very good and were easier on my stuffed knees and I found I could often use a higher cassette gear than when using a round chainring. For ME - Q-rings were much better but can't get the number of teeth I require (36T). Note also that a small 22 (or less) ovalised ring isn't worth it as there seems to be very little effect on small chainrings. However, I have lost a chain due to back pedaling on the large oval ring - once.

The other main make is http://www.osymetricusa.com/ which are very different shape to Q-rings. They also do not seem suitable for double rings on an MTB. They seem to shift poorly due to their shape, they may be ok on a roadie but the extra chain slap on an MTB seems to make them prone to shifting problems.

For me the Q-rings on an MTB were good - Except there are limited sizes and I don't think they make a N/W toothed ring.

FWIW

I'm running the Rotor 30T N/W Q-ring on my XX1, have ordered an absolute black N/W for my other bike (since it's 104 BCD and Rotor don't make a N/W for this). I'll write a review when I get it. Q-rings seem to suit me, I have them on the roadie as well. Work really good for hills.

Absolute messaged me and said it's a similar design to the rotor ring, but the peak power will come on 6 degrees sooner than the rotor ring (in the middle setting).

ptpete, i will be curious to see how you go on a single speed. the oval ring will change the chain length slightly, so you will have to introduce some chain slack, unless you run a chain tensioner!?!?

oval rings, like biopace, work on big rings with low cadance. if you like to spin fast, the ride can become very jerkey. that is why they only really exist on the big ring. i generally spin fast, so did not like it back in the early 90s. but if you like to push a big gear, give them a try....

Used a Q-ring 33T on my Rohloff hubbed Stumpjumper HT for some time. Worked ok as far as chain staying on went (no chain tensioner) and had no trouble with it - but not an SS as such Smiling

I've been running 3 x rotor q ring sets since 2010...they are the bee's knees. Helps me get up those darn hills quicker.

Most used is the middle ring of course. You're welcome to try them out if you see me on the trails.

PS they are from Spain.
....so I use only extra virgin spanish olive oil on my chain...

http://nobmob.com/node/22291

I was wondering why your knees pointed out to the side when you pedalled.

That explains it. Eye-wink

it was funny back in the 90s both shimano bio pace and Q rings were oval shaped. Both claimed similar benefits yet they were 90° to each other in how they ran in the pedal stroke.

Anyone considered how these work with a clutch RD?

As the the ring changes diameter, the RD cage needs to extend and contract.

1). Extending the cage requires you to overcome the clutch's resistance. That wasted energy isn't returned when the cage contracts.

2) Clutch duty cycle. Conservatively, If you average 40 rpm over a 2 hour ride, considering your natural cadence could be low and you're descending/pumping etc.

The ring is concentric and elliptical, meaning for every single rpm, the RD extends and contracts TWICE.

(40x120)x2 = 9,600 times per 2 hour ride your RD with complete one 'extend and contract' cycle.

The amount of movement depends on the size of the large ring. Anything 36T or under will have very little or no effect if using a Rotor Q-ring. Though the shape of the ring appears oval its actual shape means that there is virtually no 'loose' or 'tight' spot on the ring - hence it is able to be (and is sold to be) used on a single speed without any chain tensioner. 'This is not the case for the O-symetric ring which does have movement. Can't comment on the Ab-Black oval.

As noted used it on a Rohloff hub which is essentially a single speed setup for the chain, with no problems whatsoever. When on my 2x10 the derailleur didn't move as you turned the crank - so there was no extension or contraction of the RD and hence no wasted energy.

I can't say if this is the case for Q-rings over 36T, and suspect there will be some movement (extension and retraction) of the RD.

You still only have the same number of teeth in contact with the chain, with the same average distance from centre regardless of the angle of the rotation.

Have a close look Froomes derailleur in the TT of any race. 50+ teeth and no rear derailleur cage movement at all.


http://youtu.be/r8thqPDXQ1g

2:40

It's poor quality, so you can't quite see the RD cage, but you can clearly see the bottom of the chain bouncing around as it grows and shrinks.

would be rolling in his grave right about now.

What is the derailleur doing?

When the chain isn't bouncing around because of the rough road, it is doing ... nothing?

For the removal of doubt, I had a look on the Rotor USA site. It says you can use their oval chainrings on both single speed MTBs and track bikes. Track bikes are fixed gear, no chain tensioners.

http://www.rotorbikeusa.com/support.html

If it's any consolation, I wondered about it for ages, thinking it must move the RD around until I watched some road races on the telly and had an "Aha!" moment. Seeing Hans's Q-rings in action while trundling up West Head Road confirmed it. No impact on the RD. Smiling

Bees knees and Ducks feet obscure the view?

Part of the cause of the 'bouncing chain' is that the chain follows the line of the large ring - that is chain moves up and down as the large diameter and small diameter alternate as the crank rotates. It does this on the top and bottom run.

http://www.bing.com/videos/search?q=Q-ring+video...

On this one you can see just a slight movement of the RD when in the big ring - it is slight though and disappears on rings lower than 36T.
http://www.bing.com/videos/search?q=q-ring+derai...

Getting back to the origianl post question - there is little information on the Absolute Black oval ring.

absolute Black has only just become available in Australia www.scvimports.com.au . When you look at the power output in a pedal revolution the majority of us are unable to put out the same amount of power in the up stroke as we are in the down stoke. Most people are quad strong and hami weak. A well designed oval ring will address this and mean that you can overcome the weak spot in your revolution. When climbing a good oval ring can make a huge difference.

Cool SCV seem to keep the RRP sensible, sadly a 32 is useless for a 26" bike, they list a 34 but I'm guessing that will come in the future. If they make a 36T or bigger I'll buy one.

I'm interested to. This PDF suggests it's worth a try, unlike bio pace, which was setup to work in the opposite fashion to the current 'trend'.
http://www.trainsharpcyclecoaching.co.uk/images/...

An update on the Rotor Q-ring on my single speed.
It's been about a month since completing the build and have had no issue with jerky pedaling etc, in fact I can spin up some pretty decent cadence and find no issues with bounce or feeling that I'm pedaling in squares.
It can also be run without a tensioner - with the right chain ring combination of course, as I have vertical dropouts.

Have a noticed a difference?
I cant actually say, as I haven't tried my ss without the Qring.

Does the tension change whilst pedaling?
Yes it does, but it is so ridiculously minimal that you can barely notice it. The tensioner I had fitted did not move when pedaling, if this shows how little the change tension changes.

Do I like it?
Sh!t yeah! because it looks mint.

Unfortunately I don't really have any other feedback to give.

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