Many enthusiastic kids arrive at their first race only to be told that they have to "roll out" their bikes to see if they are "legal". This can be confusing and frustrating, especially if the shop they bought their brand new race bike told them it was race-ready. The international and US national cycling bodies have established standard gearing restrictions for all junior racers participating in road and track races. These rules help level the playing field for all kids, teach kids good pedaling techniques and can reduce the risk of injury.
Why Restrict Junior Gearing?
According to USA Cycling, "The main purpose of junior gear restrictions is to help the young rider develop a good pedal cadence and to avoid injury. Junior gear restrictions also level the playing field for developing juniors who may be at a disadvantage against rivals who possess physical advantages such as height and power." These restrictions reduce the likelihood that races be dominated by the early bloomers , who are physiologically years older than other kids. They won't be able to pull off monster breakaways in a huge gear that less well-developed kids can't push. Last, it helps keep junior packs together, allowing the riders to learn and refine their pack riding skills and strategies.
The one potential downside for advanced juniors is that they must ride restricted gearing, regardless of the race category in which they compete. So a 17-year-old girl competing in the Cat 1/2 field is at a disadvantage to the rest of the women she's racing. Strong racers, like Peanut Butter & Co/TWENTY 12's Coryn Rivera, can overcome this disadvantage through strong legs and technique.
What Are The Restrictions?
The test to see if a race bike is legal is called the "rollout method" or "junior rollout," which is the distance a bike travels backward in a straight line through one full pedal revolution when the bicycle is in its largest gear. The junior gear restriction for road events is 26 feet (7.93 meters).
The official checks a junior's bicycle's gears not by counting the number of teeth on the largest chain ring and smallest cassette cog, but by rolling the bicycle backward in a straight line for 26 feet. If the bicycle travels 26 feet or less when rolled backward one full pedal revolution, the bicycle is legal. If the bicycle rolls past 26 feet, the rider is disqualified for not complying with the junior gear restriction.
Race officials will usually provide a courtesy gear check prior to the start of a junior race but ultimately it is the gear check immediately after the junior race that determines whether a junior's bicycle is legal or not. It's important to keep this in mind when preparing extra equipment. If a junior racer suffers a puncture and replaces his or her wheel with one carrying a different cassette than the courtesy-checked wheel, the bike may no longer pass the post-race check. That would lead to disqualification.
To calculate how far a bike will travel relative to its gears, USAC suggests gear ratios with respect to race age and discipline. The gear limit for a rider is determined by the age of the rider and the discipline, and applies in all events in that discipline.
There is no restriction for cyclo-cross. For road and track the limits are:
Note that the gear ratios listed are merely suggestions – the distance rolled out is the governing standard.
How Do I Meet The Restrictions?
There are two methods for ensuring that a bike meets the junior gearing restrictions: using specific chainrings and cassettes/cogs that meet the criteria and "blocking" gears on standard equipment. Blocking gears on a road bike is accomplished by adjusting the rear derailleur, restricting the travel beyond the acceptable cogs. For junior track racers, blocking is obviously not an option. Blocking gears is a more affordable option for beginning racers, but is not allowed at national championship or UCI sanctioned events.
To begin, make sure the drive train is clean, freshly oiled, and shifting properly. Put the chain onto the appropriate rear cog so that the expected rollout will be met. Locate the 3 adjusting screws on the back of the rear derailleur. The upper screw is called the B-screw and it generally does not require adjusting. The lowest screw adjusts the possible range of the derailleur when it is on the largest rear cogs. Stay away from this one as turning it the wrong way can lead to the spokes playing expensive games with the derailleur.
The middle screw is the high range adjuster. Turning it in (clockwise) will limit the range of the derailleur and hence, tend to prevent the chain from engaging smaller gears. Turning it out (CCW) allows more range and will therefore allow engagement of smaller gears. To make the adjustment, start screwing the high range adjuster in (CW) until you just feel it start to tighten up. From this point, you’ll probably want to turn it another ½ turn. Now, downshift the gear lever so that it would normally allow engagement of the 13T cog and turn the crank. If it drops down to the 13T, you haven’t turned it in far enough. Make your adjustments in ½ turn increments until you just keep it in the 14T. Turn it too far and you’ll notice that the chain either jumps into the 15T or tend to skip upwards towards it. If this happens, turn the screw back out a little.
It's important to keep in mind that a 15T cog is the smallest cog that will meet the restriction with a 53T chainring. The above description assumes a 52T chainring.