Jim’s Tech Talk
Ride total: 8,835
Q&A: Can Paired Chainrings be Mixed?
An interesting question came in about modern “paired” chainrings from RoadBikeRider reader, Daniel Ramirez. You might have the same idea he had so I’m sharing our email exchange. It has kind of a surprise ending.
“On my road bike I have Campagnolo Super Record EPS components with 52/36 chainrings and an 11/23 cassette. Can I change the 36 chainring to a 39 chainring without any tech problems? I do not want to go to their 53/39 setup.”
I wrote back,
I haven’t tried what you’re proposing (switching one chainring on a Campy SR crankset), so I have no firsthand knowledge/experience whether it will cause problems shifting or not. The reason it might is because chainring sets today from Campagnolo, Shimano, Sram and all other companies making modern chainrings, are engineered as a working pair of 2 chainrings designed to be compatible with each other, not necessarily compatible with the rings from the other sets.
So, your Super Record crankset accepts three different paired sets of chainrings, which is an awesome feature. On some cranksets you can only use one set of chainrings. You have to buy a new entire crankset if you want to change your gearing. Your Super Record crank, though, accepts your 36/52 and also a 39/53 or 34/50.
These paired sets of chainrings have features designed to “time” shifts so that they happen quickly, smoothly and predictably at the optimal position during the pedal stroke. Examples of these features include specially shaped teeth (you might have noticed that the tooth shapes vary), protruding pins on the rings that catch and pick up/guide the chain during shifts, “gates” that create a gap for the chain to pass through and “ramps” that help the chain climb and drop between the rings. I pointed out some of these features in the photo, which is of a Praxis chainring (I don’t have a Campy).
Since the engineers want to provide the best possible shifting between the two chainrings of the set, each pair of rings have specific features for that set. Which means that if you substitute a ring from a different set, you might be completely messing up the paired shifting features since the two rings you’re trying to put together aren’t designed to shift together.
Having explained all that – from the crankset manufacturers’ and engineers’ point of view – I would add that there’s no reason you can’t try swapping out the 36 for a 39 and seeing if it works. If you don’t want to buy a chainring to do the experiment, you might ask riding friends if they’ve got one on their bike you can use for an experiment. I know Super Record EPS components are pretty rare out there, but it’s worth asking if you belong to a cycling club or riding group.
Alternately, you could buy the chainring, try it out and if it doesn’t work, you could surely sell it used online- or even better – maybe your local bike shop stocks Campagnolo spare parts and would work with you. If you do this, when you test the shifting with the 39 ring installed, keep in mind that you’re now using two rings not made to work perfectly with each other.
To give them the best chance to cooperate, you should go easy on pedaling pressure and choose when you shift so that it’s an “easy” shift for the derailleur to make. That will give the rings the best chance of working together and it might work well enough that you can live with it.
“Thanks for the detailed reply. It was very helpful and confirms most of my intuition. We decided to go head and try the 39 and we put it on this afternoon. And so far it appears to shift perfectly! I will ride it more and will let you know the results.”
My final thoughts
We’ll have to see if Dan has any issues down the road and lets us know. For now, I’d say it was a good move for him to try it for himself and see if the chainring swap works even if it’s not supposed to work. It would be interesting to compare the shifting features on the 36- and 39-tooth Campagnolo chainrings. It’s possible they’re not that different with only a 3-tooth difference between them. If so, that might be why the shifting didn’t get worse.
The moral of the story is that if you’re not happy with your gearing, it’s probably worth it to try what you wish you had. Just know going in that with some combinations you might compromise shifting.