Modern drive systems for road bikes are slowly evolving towards just one front chainring. Who would have thought that the double chainring setup was in jeopardy of disappearing? It wasn’t that long ago that triple chainring setups were not uncommon in general and quite common for touring bicycles. They’ve been shown the door by wide-range double chainring drive trains made possible by ten-, eleven-, and twelve-cog cassettes, which allow a wider spread of gear ratios with tolerable jumps between gears. Although wide-range doubles are possible even with just seven or eight cogs, these sacrifice tight gear jumps to get that wide range. For some folks those tall jumps are either inconsequential or are tolerated because the lower low gear is a necessity.
Now that same trend is hitting double cranksets. Campagnolo’s thirteen-cog Ekar drivetrain was the writing on the wall: there is no double chainring option—it’s just one front chainring, period. Although Campagnolo markets Ekar for so-called “gravel” bikes, this is just because it’s the market that is ripest for one-by. In this year’s Tour de France the eventual winner Jonas Vingegaard used a single chainring set up for a few stages in this year’s race as well as in the Criterium du Dauphiné, which he also won. (These were presumably twelve cog setups unless SRAM was secretly trialing a thirteen cog drivetrain.)
It’s hardly a deluge of one-by’s but it’s a start and an ominous one as the hype of one-by is relentlessly propagandized online by the cognoscenti. The advantage of one-by is ad nauseum repeated like a holy liturgy: (1) eliminating the front derailleur and second chainring means a lighter bike; (2) it’s more aero with all that drivetrain furniture gone; (3) it’s easier because you’re too inept to shift a front derailleur; and (4) double chainrings have a lot of duplication of gear ratios so it’s not really useful. Realistically do any of these arguments apply to the real world? Aero and light weight are awesome for going fast but the difference these specific changes make is irrelevant except perhaps at the highest racing levels. And how many of us are racers let alone World Tour racers?
Shifting a front derailleur does require some skill. Indeed shifting gears must require some skill since I see a lot of people riding in their highest gear while struggling up steep hills so scared are they to touch their shift levers despite all the progress road bike drivetrains have undergone to make shifting easier. Today’s electronic shifting systems have essentially completely de-skilled the entire process and made shifting bicycle gears analogous to shifting a car that has an automated manual transmission: you just select a gear and the system does the rest. In the days when all shift levers were ‘analog’, ie. friction shifters, there definitely was a learning curve to shifting gears accurately and quietly akin to learning to drive a car with a manual stick shift: there was a whole lot of grinding going on until you got the timing of your shifts down! Even indexed mechanical shift systems, which we’ve been living with since the late ’80s, require some skill since you could still move the derailleurs partway just be pressing lightly on the shift levers and you can still mistime a shift and grind your gears away. Not so with electronic shifting!
The horror of duplicate gears is mostly baloney. Unless you’re an acolyte of half-step plus granny shifting—if you even know what that means—those duplicate gears also function to keep you shifting just the rear derailleur until you absolutely need to shift the front derailleur when you’ve come to either end of your cassette. No one needs 20, 22, or 24 completely different gears but what you probably do want is to be able to move up and down the cassette comfortably while minimizing shifting the front chainrings, i.e. avoiding double shifts as much as possible.
Now a company called Classified has come up with another take on one-by allowing you to have your cake and eat it too. Classified’s system is one-by but with a clever rear hub with a planetary gear that allows you to shift to a lower ratio with just one front chainring. And it’s done electronically and wirelessly! If you grew up with Sturmey-Archer three-speed rear hubs, then you’re already familiar with this idea since it too was a planetary gear hub that had two additional gear ratios. Shimano, Rohloff, and Sram also make planetary gear rear hubs so this isn’t a new idea at all. But in those systems the planetary rear hubs are designed to eliminate the rear cassette whereas Classified’s system preserves the cassette and eliminates a front chainring. Classified’s genius is in making such a system electronic, wireless, and relatively light. With just one front chainring you get the same number of gears you’d get in a double chainring setup. Classified claims that there isn’t a weight penalty with that rear hub but I’m not convinced that’s entirely true; it probably depends on which specific drivetrain you’re running. By pressing their shift button you can instantly lower the effective gear ratio by 68.6% while still in the same chainring. For example, if you’re using a 50-tooth chainring, then Classified’s second gear makes that equivalent to a 34-tooth chainring. The real tradeoff is in dollars: that Classified system costs about $3,000 including a wheelset. Classified’s system generally has gotten positive reviews online although it’s too early to assess the longevity and long term durability. Nonetheless I’m intrigued by this ‘solution’…
My interest however is not in eliminating the double chainring but in getting lower gears that replicate a triple by adding this system to a double. It’s almost impossible to get a high quality triple crankset plus the accompanying derailleurs anymore. And if you like indexed shifting as I do you’re going to have to go down pretty far on Shimano’s groupset hierarchy to the Tiagra level to find a triple crankset or else look on EBay for used or NOS parts. (Sram has never made a triple and Campagnolo has completely stopped producing them.) But what about a Classified system with a double chainring? If you add it to a 50/34crankset, you then get a 23-tooth granny equivalent. If you pair this with a tight 11-25 eleven speed cassette, you get a very nice spread of gears going from 123 to a low 25 gear-inches; if you instead use a 11-28 cassette, you get an ultra low gear of just 22 gear-inches. This is mountain bike territory! What makes this gearing extra delicious is that the gear jumps are just one tooth from 11 to 17 and then two teeth to 25, giving you not just a wide range but small jumps so that you can find exactly the right cadence. The icing on the cake is that you don’t have to do a lot of shifting gymnastics—you can stay in one front chainring (or virtual chainring) most of the time.
If you look at the gear ratio chart below you can see that my hypothetical Classified double set up compares well to a triple. The gear jumps up and down the cassette are almost all reasonably tight. Compare either the triple of the faux triple Classified to a compact double with approximately the same range and you’ll see that the latter has bigger jumps because to get that spread you need more two-, three-, and even four-tooth jumps. To find a gear with a comfortable cadence you’re doing to have to do more front chainring shifting whereas the triples obviate most of that.
But there’s always a catch, isn’t there? The wireless system is built into the the Classified rear hub’s thru axle, so quick release skewers are out. That leaves out all older bikes. If you have a modern road bike built for disc brakes, you’re probably fine as they are almost entirely made for thru axles. But retrofitting the Classified system to a bike built for quick release levers is going to involve a lot of messy work, ie. replacing the rear dropouts and possibly having to spread the rear triangle to accommodate a wider hub. For old school steel frames this is doable but unless that frame is your soul mate you’re probably better off getting a newer frame that accommodates a thru axle.
Of course the point of all this is irrelevant if you’re the kind of cyclist who is not sensitive to cadence, in which case having big gear jumps doesn’t bother you.
The Chain Letter 