Mountain bike technology has come a long way since its invention in the late 1980s. Most importantly, the mountain bike gear system has seen significant advancement over the recent years and has influenced the way people ride bikes and the type of bikes being introduced in the market. Conventionally, the human muscles can sustain a cadence (speed of pedaling) of 60 to 110 crank RPM (revolutions per minute). So, changing gears allows you to maintain appropriate speeds in different terrains. Here is a quick guide on the recommended descending and ascending gear ratios for bikes.
Gear Ratios Explained
The gear system comprises several parts, namely, cassette, derailleurs, chain, chainset, and shifters. Gear ratio refers to the ratio of the number of chainring teeth to the number of teeth of the cog on the cassette. Your choice of the chainring and the sprocket determines the gear ratio. Assuming that you are riding at your largest chainring of 50T (teeth) and smallest 12t cog, the gear ratio at the moment is 50: 12. This ratio (50: 12 = 4.2: 1) means that the gear multiplies every turn of your pedal to make the wheel of your bike rotate at approximately four times. A larger gear is hard to push but provides you with greater distance for every rotation of your pedal.
On the contrary, you will be required to select a small ring at the front and a large cog at the back to obtain a low gear ratio, and consequently, more comfortable gear. The reason for the combination is that the rings are the closest similar, so you obtain a low gear ratio. Typically, this would be 34 teeth at the front and 32 teeth at the back to provide a ratio of 1.06: 1.
Climbing Gear Ratio
You certainly don’t want to deplete your energy when climbing steep terrain. Accordingly, you should choose a lower gear ratio that will make it easier for you to pedal up the hill. Otherwise, if you are endowed with more healthy muscles and massive energy, you may opt for a higher gear ratio that will require you to work harder than someone using a low gear ratio. Nevertheless, make the work easier by selecting a lower ratio. For instance, considering the previous example of low gear ratio, 1.06: 1, it means that you are moving the back wheel through one revolution with every turn of the crankset. Moreover, the gear ratio allows you to spin your wheels quickly and easily up the hill.
Descending Gear Ratio
The recommended gear ration for descending a hill is entirely opposite of gear ratio choice for ascending a hilly terrain. When riding downhill, opt for a high gear ratio which allows for a greater number of revolutions per pedal cycle. This translates to a combination of a large chainring and a small cog. Additionally, a high gear ratio is also suitable when biking on a flat surface whereby although you require much effort to get the bike moving, you move quickly.
Your choice of gear ratios for your mountain bike when ascending or descending a hill determines the ease and speed of your ride. Therefore, when riding downhill, opt for a larger chainring and smaller sprocket to obtain a higher gear that will enable you to descend a hill quickly. On the contrary, select a low gear ratio for an easier climb.