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Osymetric Chainring For Campagnolo?

by craig749
Fri, Aug 22, 2014 12:43
4

A friend of mine has been using osymetric chainrings recently which got me thinking about possibly trying them out. The difference is that he uses Shimano and I'm using Campagnolo Chorus.

After looking around online it doesn't look they exist for Campag? Is this the case or am I missing something?

Thanks

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velotech_cycling | 9 years ago
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Neither Di2 nor EPS will fix this problem and neither Campagnolo nor Shimano (or SRAM for that matter) recommend the use of any form of non-circular chainring.

The problem is that the height of the chain and the distance "back" down the derailleur cage is constantly varying with any non-round chainring, whereas the design of the inside of the FD and the rigidity of the cage of the FD are calculated on the basis of knowing where the chain will be at the time the shift starts and finishes execution - obviously, if the chain is in effect rising or falling relative to the position of the FD cage as the shift is actually happening, that relationship is changed and shifting will be compromised.

The mount of shift force makes little or no difference.

Added to this, not as bad with Rotor as with Osymetric, is that on downshift, the chain is hitting the outside plate of the FD further back (with Osymetric, much further back) than the designed parameter for the outer plate and so the rear end of the FD is in effect imeded from moving towards the frame as it should - the chainring then "hangs onto" the outer ring for a fraction and in doing so stresses not only the FD, but also the FD mount more than it should.

This is an additional element in the poor downshift and also in the far higher failure rates of FDs used with non-round chainrings.

We see problems with FD mount rigidity from time to time - the rigidity of the FD mounting has a material effect on the quality of the front change, whatever chainset / FD arrangement is used - a more flexible FD mount will compromise FD performance & if the FD performance already has a problem due to the use of non-round chainrings, then a "soft" FD mount will only make matters worse.

Whilst on the subject of FD mounts, they rely on being at a certain distance in front of / behind the axis of the chain set to position the FD correctly for shifting - this is related to the radius of the FD cage and that of the chainrings. Since non-round chainrings effectively change the radius of the chainring constantly, twice per revolution (that is, after all, how there are designed to work) this fore-aft positioning of the FD is also compromised.

Some non circular rings are an additional problem with a braze-on mount because the available height adjustment in the mount may not be enough to allow setting the FD high enough to cope with the major diameter of the chainring when the chain is on the largest sprocket at the back.

HTH
Graeme
Head tech
Campagnolo Main UK SC

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craig749 | 9 years ago
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Thanks glynr36. I thought that Rotor Q Rings would be the best bet. Have you ever tried them or know anyone who has? I've read a few reviews with lots of people saying they are a pain to fit if you have a braze-on mech?

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giobox replied to craig749 | 9 years ago
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craig749 wrote:

Thanks glynr36. I thought that Rotor Q Rings would be the best bet. Have you ever tried them or know anyone who has? I've read a few reviews with lots of people saying they are a pain to fit if you have a braze-on mech?

I run Q-rings with a braze-on front mech. I can't see how the mech attaches to the frame could make any difference to installation difficulty, its pretty much the same job braze-on or band-on.

The big down side is shifting performance simply isn't as good, at least compared to the really quick and smooth shifts you'll get on the top end Shimano/SRAM/Campag stuff. The chain also has an annoying habit of 'skating' if you shift from big to small while cross chained. Sure, you shouldn't cross chain, but we all do it occasionally. I've seen this behaviour on several friend's Q-ring equipped bikes too.

Personally I don't think this is worth it for a benefit that may or may not actually exist. For what its worth, Rotor's own marketing numbers put the increase in lactate threshold at only 5 percent, and I'm guessing this is the best case. I'm fairly sure the whole thing is a gimmick, but Rotor cranks are the only thing that natively fits the BB on my Cervelo. Assuming I don't buy a completely new bike before I wear the rings out (never a safe assumption...), I will definitely be changing to a no-Q or Praxis Work set.

If you run Di2 or EPS this probably won't matter. The torque in the electric front mechs is so strong they will shift instantly on pretty much anything at any speed. The much gentler tug of a mechanical group's cable just doesn't engage all that well on them.

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glynr36 | 9 years ago
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They don't make Osymetrics in Campag BCDs (they're not the same as everyone elses)
Closet you could get are Rotor Q Rings, which are different though.

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