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Technical FAQ: Junior gear options

Lennard Zinn explains how junior racers can make the most of modern components to get good gear ranges that don't break the rules.

Dear Lennard,
I’m a junior coach who is super frustrated about the component manufacturers not offering cassettes for junior gearing. It was terrible with 10-speed hubs, but now it’s impossible with 11-speed. I can’t find a single 11-speed cassette that has a small cog of 14 teeth. In my years of coaching Minnesota Juniors, I have talked to people from SRAM, Shimano, and Campagnolo about this, and nothing has changed. These kids are our future, and if they don’t supply the parts they need, how are we supposed to keep juniors racing on the road?
— Dag

Dear Dag,
You have talked to me for years about this, and I think I have found a couple of really good solutions. I think the key to this is to forget about the cassettes — they are very expensive parts to produce (making aftermarket solutions hard to come by), and there are lots of other bike consumers already out there hammering the component companies for their own favorite gearing choices. Instead, the key is to do something with the chainrings.

For those unfamiliar with the issue, juniors are restricted to a maximum gear ratio on the road, and, even more stringently, on the track. Bicycles of competitors in these events must pass a “rollout” at every race, where the official turns the crank one turn and measures how far the bicycle rolls in that one crank rotation. To pass the test, competitors are not allowed to “block” the rear derailleur (tighten the high-gear limit screw) from reaching the smallest couple of cogs; the highest gear on the bike is the one tested. There is no junior gear restriction for cyclocross or mountain bike racing.

Maximum road junior gear rollout for ages 6-18 is 26 feet (7.93 meters), which is closely approximated by a 52×14 (52-tooth chainring, 14-tooth smallest cog) and a 700 X 23C rear tire. If you look at a gear chart, you won’t find a number anywhere near as big as 26 feet, because you have to multiply numbers on gear charts by π (3.1459, or 22/7) to get the distance the bike rolls in one rotation. A 52×14 is a 98-inch gear on a gear chart based on a 67cm-diameter tire (close to most 700 X 23C tires). Changing the chainring rather than the cassette can help.

A 41×11 is the same size gear as a 52×14. A 44×12 and a 48×13 are just slightly smaller gears (97 inches). The vast majority of 11-speed cassettes start with an 11-tooth cog, but Shimano and Campagnolo offer 11-speed cassettes that start with a 12-tooth cog, and Shimano and Miche offer 11-speed cassettes that start with either 13-tooth or 14-tooth cog. So options are opening up for juniors.

Enter Wick Werks with a great solution: small chainrings for compact (110BCD) chainrings and an adaptor for the front derailleur to work with them. Wick Werks not only offers great sizes for exactly the problem of a cassette with an 11T small cog, namely a 110BCD 41-33T chainring pair, but it also does it with its full “Bridge Technology” shift-ramp machining on the 41T ring.

Of course, if the kid’s bike has a front-derailleur braze-on (integrated mount on the seat tube), you won’t be able to slide the front derailleur down far enough to shift such small chainrings. Wick Werks also has the solution for that, namely a machined adaptor that bolts to the braze-on and the front derailleur and moves it down to the right height to shift well on the 41-33 rings.

The kid will have plenty of low gears, since a 33×32 is a 27-inch gear, a 33×29 is a 30-inch gear, and a 33×28 is a 31-inch gear.

The other great option is a road 1X11 drivetrain. SRAM Force 1 or, more junior-priced Rival 1 would be a great solution for a kid getting a new bike. To not drop the chain, it depends on SRAM’s X-Horizon rear derailleur with a clutch designed to prevent chain slap, and the X-Sync chainring, which has tall teeth that are fat-thin-fat to fit into the wide-narrow-wide spaces in the chain between pairs of outer-inner-outer link plates.

With an existing SRAM-equipped bike, you need only substitute the chainring and rear derailleur to make a SRAM road “one-by” system work, whether it is 10-speed or 11-speed. In other words, you could run a Rival 1 or Force 1 X-Horizon rear derailleur and X-Sync chainring with a 10-speed cassette (and 10-speed or 11-speed chain), if you have SRAM 10-speed shifters.

Unfortunately, if you’re running 11 speeds, SRAM road X-Sync wide-narrow chainrings don’t come in 41T; you would have to use a 40T, which is a two-inch smaller gear (rolls out half a foot shorter). But if you are running 10 speeds, there are lots of cassettes available that start with a 12T, and you can get a 44T X-Sync wide-narrow chainring and only have an inch smaller gear than a 52×14 or 41×11.

If you want to use a four-arm Shimano crank with SRAM one-by, Wolf Tooth Components makes X-Sync-style chainrings with tall, wide-narrow teeth, but again, there’s no 41T.

Upgrading wheels to 11-speed freehubs may be prohibitively expensive for some juniors, since an 11-speed SRAM or Shimano cassette requires an 11-speed freehub body, which is 2mm wider than 10-speed. In many cases, this requires a new 11-speed wheel, since not all 10-speed freehubs are interchangeable with 11-speed. In an instance where Campy saves money for a junior, switching from a 9-speed or 10-speed Campagnolo cassette to 11-speed requires no change in freehub bodies. And a wonderful compatibility exists for this, since the spacing between cogs (cog pitch) is the same for all 11-speed cassettes; you can use a Campagnolo 11-speed cassette with a SRAM 11-speed drivetrain, just as you can do that with a Shimano 11-speed cassette.

As for getting enough gear range for a small kid, you can get an 11-36 cassette, which should give plenty of low gear with a 40T chainring on the front. SRAM offers a full range of sizes between 11-25 and 11-32 as well, and Shimano offers 11-23 to 11-32 cassettes, which, of course, fit on the same 11-speed hubs and work fine with SRAM drivetrains. For kids with wheels with Campagnolo freehub bodies, 29T is the largest rear cog Campy offers. A 40×32 is a 33-inch gear, a 40×36 is a 29-inch gear, and a 40×29 is a 36-inch gear.

For those who are wondering, yes, with an XD driver, you can even use an 10-42 cassette, but the rollout with that would require a 37T chainring, and 38T is the smallest available from SRAM or Wolf Tooth for a road 110BCD crank.

Rather than being a time where juniors are totally screwed, having to use old bikes with 6-speed cassettes or something to meet the gear rollout, I think these options open it up more for junior road racers than it has been for a long time.
— Lennard