Understanding Gear Ratios:

7 Aug

Understanding Gear Ratios:

Cycling Tips 12

cycling tipsSelecting  the best gears for your bike will obviously create a more pleasing, less tiring and faster cycling experience.

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 incycling tips 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.

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Normally, your crankset will have these three different setup options:

  • cycling tipsThe standard 2 chain ring setup usually has a large chain ring containing 53 teeth and small ring containing  39 teeth.

  • cycling tipsThe 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.
  • cycling tipsThe compact 2 chain ring setup normally has a large chain ring containing 50 teeth and a small chain ring containing 34 teeth.

Most of the rear cassettes in use today are usually 9, 10 or 11 speeds.  This number indicates the number of cogs on the cassette.   This also represents the number of gear options available to you.cycling tips

 

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.

cycling tipsSo, the higher the gear inches number, the harder it is to turn the pedals (high gear).  Conversely, the lower the gear inches number, the easier it is cycling tipsto turn the pedals (low gear).

 

This information can be useful in many ways.  One such situation is if you’re a junior and just starting to enter races.  As a junior, you can only race with certain gearing or a limit on the high end.cycling tips

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:

cycling tipsTake 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.

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The charts above are the gear ratios with different combinations.

cycling tipsYou 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.

cycling tipsMost 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.

Get the gearing down on your ride and get faster with less pain.cycling tips

 

 

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