Friday, 25 July 2014

Complete guide to bike gearing

Understanding how gears work is crucial for any road cyclist who wants to ride efficiently — and quickly!

The gear system on a modern road bicycle is made up of nine component parts: two integrated levers; two gear cables; two derailleurs; a cassette of different sized sprockets at the rear wheel; a crankset or chainset of different-sized chainrings connected to the pedals; and the chain.

It’s actually a very simple set-up. The left lever operates the front derailleur, the right lever operates the rear derailleur, and these move the chain between sprockets or chainrings. The different sized sprockets and chainrings offer different achievable speeds, however, they also offer different options in terms of pedalling ease. So a rider cycling down a slight incline won’t have a problem going quickly pedalling the biggest gear ratio available, but going up hill they will want an easier gear, with the compromise being they’ll have to go slower.

On the cassette at the rear wheel it’s possible to have anything up to 11 sprockets. The bigger the sprocket, the easier it is to pedal, but the slower the rider will travel. The smaller the sprocket, the harder it is to pedal, but the quicker the rider will go. Modern road bike cassettes range from smallest sprockets of 11 teeth to biggest sprockets of 32 teeth.

At the chainset it’s possible to have anything up to three chainrings (this set-up is called a ‘triple’ chainset). However most current road bikes use what is known as a ‘compact’ chainset, which has two chainrings, a the smaller inner ring with 34 teeth and a wider outer ring with 50 teeth. When it comes to ease of pedalling and achievable speed, the situation with chainrings is the opposite of cassettes — small chainrings are easier to pedal but slower, big chainrings are harder but faster.


How to use your gears

What’s the point of bike gears and how should you use them? Really, every cyclist’s aim should be to maintain a steady cadence, or constant rhythm of their pedal stroke. The quicker a cyclist can spin their pedals consistently, the easier it is on their legs and the more work their heart and lungs do. The slower and harder they push, the more their leg muscles take the strain. But leg muscles tire a long time before heart and lungs.

Assuming you would rather be aerobically fit with healthy heart and lungs, rather than anaerobically fit with bulging leg muscles, a reasonably high cadence is important. It’ll also mean you’ll all be able to cycle further without getting tired. For most leisure riders a cadence of something like 80rpm is good, while professional road cyclists can pedal at cadences of 100rpm or more.

In theory you can use any combination of rear sprocket and front chainring to maintain this steady cadence. If a bike has 10 sprockets at the back and two chainrings at the front, that would offer a total of 20 different gear ratios.

However, there are some caveats. For example, you should avoid putting the chain through extreme angles. Try not to use the smallest sprocket at the back and the smallest chainring at the front at the same time — simply push the chain onto a biggest chainring at the front if you want to go quicker. Likewise don’t use the biggest sprocket and biggest chainring at the same time, simply drop the chain down to a smaller chainring if you need an easier gear.

In these extreme settings you may hear the chain rubbing against the front derailleur cage — that’s not an efficient sound for a cyclist. Remember: using gears is all about producing the most efficient result from your pedalling.

One final tip: inexperienced cyclists have a tendency to attack challenges in the biggest gear possible and only change down when they are in dire straits. This is not efficient cycling and can lead to accidents — changing gear while the system is under load, such as while you’re struggling up a climb, is more likely to result in a derailleur failing.

So when you come to the bottom of a big hill, select a gear ratio you can maintain and keep a nice steady tempo all the way up. It’s the most sensible way to cycle and it won’t mark you out as a rider with all the gears, but none of the ideas!