Cycling Tips 12
Let’s face it, many of us do not ride just on flat roads, so in order to sustain your cadence and power over a diverse terrain, the decision you make in regards to your gearing, will make a profound difference when getting your bike dialed in.The two main areas on the bike to look at are the Crankset and rear cassette.
Normally, your crankset will have these three different setup options:
- The standard 2 chain ring setup usually has a large chain ring containing 53 teeth and small ring containing 39 teeth.
- The triple or 3 ring setup normally has a large chain ring containing 52 teeth, middle ring containing 39 teeth and a small chain ring containing 30 teeth.
- The compact 2 chain ring setup normally has a large chain ring containing 50 teeth and a small chain ring containing 34 teeth.
What’s gear ratio?
Gear ratio refers to the ratio of teeth between a chainring in the front and the rear wheel’s cogs in the back. Gear ratios serve to convert between the revolutions the wheel travels and the revolutions the cranks turn. “Gear inches” is how far you travel with one complete turn of the pedals.
Another situation is if your installing a new gear combination and want to limit overlap between your gears.
Your highest and lowest gear ratio will be determined by the crank set and the number of teeth on the smallest and largest cogs. To figure out your highest and lowest gear ratios, complete the following:
Take the number of teeth on your large chain ring and divide it by the number of teeth on your smallest cog. The resulting number indicates your highest gear ratio and gives you the number of times your wheel will turn with one turn of the crank.
Next, take the number of teeth on your small chain ring and divide that by the number of teeth on your largest cog. This will be the lowest gear ratio you can achieve with your current gearing setup and will indicate how hard or easy it will feel to climb.
Here is the formula to figure out gear inches. WxF/B, where W is the tire’s diameter, F is the tooth count in the front (chainring), and B is the count in the back (cog). Or, 27x(42/25) = 45.4 gear-inches.
The charts above are the gear ratios with different combinations.
You also should note that the gear ratio is the same for the 53 x 15 and the 39 x 11. However, if your wanting to use this gear ratio, you should take note that being in your 39 x 11 gearing will create a severe cross over with the chain, creating more friction and wear.
Knowing what an optimal gear ratio’s for you will take some miles and a little trial and error. It all depends on your riding style and experience.
Most riders do not run out of gears on the flats but can just about always use another gear when climbing. The rule of thumb is, if you can’t maintain a cadence of 80 on a long hill of around 6 to 7 percent grade, then you should think about utilizing a bigger cog on the back.