by Lars Hundley
Looks like SRAM is going in a different direction with 12 speed than Campagnolo. Where Campy aimed for and achieved a cluster of gears with few gaps in between to allow riders exactly the right gear choice in the back, SRAM appears to be expanding the ability to use a smaller minimum cassette cog over to their road groups, as they have already done with their single chainring mountain bike and gravel groups.
The new eTap prototype spotted recently on a Katusha-Alpecin pro team bike at a Japanese criterium not only had 12 gears in back, but was also using the XD style of hub that allows a smaller 10 tooth cog instead of 11 with a standard road cassette. Cogs on the cassette make a bigger difference in gear inches than chainrings, which means that you could use a smaller front chainring and still get the same top gear. As an example, a 48 x 10 is the equivalent of a 53 x 11.
Right now, the only prototype cassette we’ve seen in action has been a 10-28. But if SRAM also offered a larger maximum cog in the rear, a 48/35 chainring set up in front could give cyclists lower available gearing for steep and long hills, and still also include the highest gearing that is left out of a traditional compact or mid compact chainring setup that only has an 11 tooth cassette. With the current 28 tooth SRAM cassette we’ve seen so far, Campy’s 12 speed with a 32 tooth cassette option still has an upper hand, with a larger overall gear range.
Rumor has it that Shimano is also about to announce its own 12 speed group soon too, which means that Shimano, SRAM and Campy will all have 12 speed options. I wonder which direction they will take 12 speed, and whether it will be closer to Campy’s solution that sticks with a traditional 11 tooth, or something more like SRAM.
Questions remain. What does this mean for our existing wheels as all three manufacturers go to 12 speeds? Will we be able to just convert the freehub and still use them, or will the spacing change, requiring us to buy all new wheels again? Will 12 speed spacing be cross-compatible between all three brands? How long will a 10 tooth cog last compared to an 11 tooth? Is there enough chain wrap with 10 teeth for the most powerful pro roadies to prevent skipping at maximum efforts, like during sprints?
The 10 tooth issue has already hit me personally, with the recent purchase of a Giant Revolt 1X all-road / gravel bicycle that uses the new SRAM XD hub. My original intention was to upgrade the relatively low-end wheels that came with the bike to a set of DT Swiss wheels I already owned that are lighter and faster. I thought I would finally be able to consolidate down to one standard of road disc wheels that would be compatible with all of my 700c bikes.
But I quickly found that the SRAM XD hub on the Revolt means that if I use the DT Swiss rear wheel, I’ll miss out on the 10 tooth gear. And since the Revolt only has one chainring, that really reduces my highest gear if I don’t have the 10 tooth in the back. Back to the drawing board. Could a SRAM XD hub and cassette with 10 teeth in the back work with my Ultegra Di2…?
Learn more and see photos at Cycling Weekly and Cycling Tips.
Special thanks to Jim Langley for spotting the SRAM 12 speed news, and for checking my work for technical errors before publication.
Richard Henley says
In addition to the points made in Mr, Hundley’s interesting article, my experience suggests that a 10-tooth sprocket will wear rapidly. Additionally, such a small sprocket would likely result in a small amount of accelerated chain wear. A 10 tooth sprocket may fill a niche for specific needs,and it would be nice to have this size as an option, however, from my perspective, it will not replace the 11-tooth sprocket.
Now here is some real heresy. I think there may be merit in the industry standardizing on a cassette’s “normal” small sprocket, at 13-teeth , and sizing up the chain-rings to maintain the overall gear ratios.