gears are a fundamental part of a bicycle they allow you to take on steep climbs and keep the pedals turning on the flats all at the same time but how do they actually work the gears on a bike can be broken down into three areas of componentry the chain rings including the front derailleur the cassette including the rear derailleur and pulley wheels and the shifters the chain rings are attached to the cranks and most road bikes have two of them chain rings are defined by the number of teeth on the inner and outer rings and these day setups of road bikes can be grouped into three categories standard semi compact and compact a standard chain set has 53 teeth on the big ring and 39 teeth on the inner a semi compact has 52 teeth on the outer ring and 36 on the inner ring and a compact has 50 teeth on the big ring and 34 on the inner ring a standard change that has the hardest gears of the three setups while the compact has the easiest the group of cogs attached to the rear wheel is the cassette most road bikes will have between nine and twelve cogs ranging from 11 T from the smallest cog up to 32 teeth on the biggest the number of cogs determines the so called speed of the bike nine cogs means a nine-speed bike and so on the derailleurs are operated by the shifters on the handlebars the derailleur shift the chain between the inner and outer ring on the front and the cogs on the cassette on the back the front derailleur is operated by the left shifter and the rear derailleur by the right so that's a bike's gears in a nutshell but what about gear ratios a gear ratio is expressed simply as the number of teeth on the chain ring this is the number of teeth on the COG of the cassette the chain is currently sitting in this then determines the number of rotations your rear wheel will make for one complete pedal stroke for example if you are in the big ring on the front let's say it's a 52 and the smallest cog on the back let's say at 12 then the ratio is 52 to 12 then you just divide the big ring number by the small ring so 52 divided by 12 to give you the number of rotations in our example 4.3 so one turn of the pedals will result in 4.3 rotations of the wheel that would be our biggest gear of course with each pedal stroke resulting in the greatest distance traveled the reverse is true in relation to the smallest gear with a chain in the small ring a 36 for example on the front and the biggest cog on the back said 28 the result would be 36 divided by 28 giving us just 1.2 rotations of the wheel for one pedal stroke this gives us the least distance but is ideal for climbing to help keep the cadence as high as possible the moral of the story is obviously to you're gearing right next time you're in the market for a new bike if you love climbing then a compact or semi compact setup will be best while for racism rulers standard might be more appropriate it's a question of your preferred cadence as well locai dense riders will prefer more traditional setups while high cadence riders generally prefer more modern compacts having said that Lance Armstrong was known as a high cadence rider he generally like to ride above 90 RPM and he used a 22 teeth cassette on his standard setup for the hill climb on stage at 11 at the 2001 tour he had used a 23 on the previous day's climb up outdoors and rumor has it he felt that was too low Mazen mat up a 13 kilometer climb with an average gradient of 8% chapeau