Technical FAQ: Options for increasing rear derailleur capacity

Have a question for Lennard? Please email him at veloqna@comcast.net to be included in Technical FAQ.

Dear Lennard,
I hope you can give me advice on Campy Super Record 11spd gearing. I have a 34/50 crank and a 29t cluster. Can I make this work with a 34t cluster? I assume a long cage from a lesser group might be needed. And I’m not sure what to search for an 11spd compatible cluster that has a 34t cog? Or, can I replace some Campy cogs to my cluster to widen the range? I seem to recall seeing a hanger that lowers the derailleur below the standard mount to allow wider range, but not sure if that is the answer or part of the answer? Anyway, getting old seems to go along with lower gears…

And I also had an ablation a few years ago and am doing pretty well.
— Robert

Also read:

• Technical FAQ: Zdeněk Štybar’s cardiac ablation and timeline for return to cycling
• Technical FAQ: Questions about blood flow reduction post-ablation and SVT

Dear Robert,
There is no factory option for shifting a cassette with a 34-tooth large cog with Campagnolo 11-speed derailleurs. In 2018, the company introduced a medium-cage 11-speed derailleur in Chorus, Record, and Super Record that had a maximum sprocket capacity of 32 teeth. The medium cage doesn’t reposition the upper pulley to clear for larger sprockets; it just takes up extra slack of the longer chain required by the larger cog. It won’t provide enough clearance for a 34-tooth cog.

Buddy Spafford, North America Technical Service director says, “Any of the Chorus, Record, or Super Record derailleurs from 2015 or later can be updated with the medium cage from 2018 and should work with our 32t cassettes. The original versions of 11-speed from 2009-2014 are not officially compatible even with the medium cage since they were not designed to handle such a large-capacity change.”

While there may be some slight differences between derailleur hangers that may offer a bit more capacity on one bike than another, chances are you won’t be able to use a 34-tooth cog with a stock medium-cage setup. As you mentioned, to keep your 11-speed drivetrain and run that big of a cassette, you would have to experiment with lengthening your derailleur hanger; it will indeed be part of the answer. One option is the Wolf Tooth RoadLink. It will provide the clearance from the large cog that the derailleur needs, but it won’t work like a derailleur designed for that cassette. It may shift fine; you won’t know until you try it.

Glad your heart’s doing well.
― Lennard

Dear Lennard,
My Di2 2X11 gravel bike does not have low enough gearing. Do you have any suggestions? Do I scrap the whole drivetrain?
— Mark

Also read: Technical FAQ: Shimano GRX chainrings, tubeless-ready road tires with tubes, rivnuts

Dear Mark,
You haven’t said if you have GRX Di2, Dura-Ace Di2, or Ultegra Di2, so I’ll answer generally. First off, it probably goes without saying that to run a bigger cassette, you’ll need to get a longer chain, so that piece of the drivetrain will need to be replaced.

For a minimum of expense and hassle, you can always switch out your derailleur’s direct-mount (DM) link with a Wolf Tooth RoadLink DM, assuming your derailleur is a direct-mount (i.e., recent) type; the RoadLink DM fits GRX 810 (RX810), R7000 105, R8000 and RX800 Ultegra and R9100 Dura-Ace rear derailleurs.

If you instead have an older-style derailleur, where the upper knuckle of the derailleur bolts directly to the derailleur hanger rather than to a direct-mount (DM) link arm that sets the derailleur back from the derailleur hanger, then you would use the standard RoadLink, which just lengthens the derailleur hanger, rather than increases the offset of the derailleur to the rear the way the RoadLink DM does.

If you have a rear derailleur with the short (SS) cage, you can certainly buy a new rear derailleur with the longer, GS cage. And if your current derailleur is non-DM, you can replace it with a DM Di2 RD, and your shifters will send commands to it just fine.

You can also switch out the jockey-wheel cage alone. If you have a DM SS rear derailleur you can interchange cages with a DM GS rear derailleur. If, on the other hand, you have a non-DM SS rear derailleur, you can interchange cages with a non-DM GS rear derailleur.

As you can see, those links for the medium cages are to non-Di2 rear derailleurs. That’s because the cage is the same, and you can save money by switching the cage from a non-Di2 rear derailleur onto your Di2 rear derailleur. You can also switch across model platforms; if you have a Dura-Ace rear derailleur, you can use the cage from an Ultegra rear derailleur of the same generation (both DM or both non-DM RDs). You may have success buying the cage alone, though I have found it hard to find small replacement parts these days.
― Lennard

Dear Lennard,
My gravel bike is equipped with a mechanical SRAM Force 1. I did some research on the Internet, but it is still unclear to me what exactly I need to change in order to migrate to an AXS “mullet” build. I hope you can help me identify what needs to be changed. Can I only change the rear derailleur, shifters, cassette, and chain? Or, do I also need to change brake calipers, crankset, and chainring?
— Andre

Dear Andre,
You do need to change the parts you list, and you also need to change the chainring to one that is compatible with the Flattop 12-speed chain. You can use the same brake calipers and crankset.
― Lennard

Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder (www.zinncycles.com) and purveyor of non-custom huge bikes (bikeclydesdale.com), a former U.S. national team rider, co-author of “The Haywire Heart,” and author of many bicycle books including “Zinn and the Art of Road Bike Maintenance,” “DVD, as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.” He holds a bachelor’s in physics from Colorado College.

Follow @lennardzinn on Twitter.