There’s an art to choosing the right gear called “riding a straight chain”. It reduces the risk of throwing your chain off the sprockets when you change gears and it looks after your hip pocket because there’s less wear and tear on your components.
Riding a straight chain is literally about choosing the right gear to keep your chain straight. Isn’t it always straight? Take a look at what it does as you move up and down your gears. You’ll see the angle changes. Most mountain and hybrid bikes have three chain rings and between five and nine sprockets on the freewheel at the back. Sight down your chain and you’ll see the big chain ring (at the front) lines up with the small sprockets (at the back), the small chain ring with the big sprockets.
A simple rule of thumb keeps things straight. When you’re in the small chain ring avoid using the last three small sprockets. When you’re in the middle chain ring, keep away from both the largest and smallest sprockets. And when you’re in the big chain ring leave the three large sprockets free.
That’s all very well, but if what if I need that gear? Gears are all about the ratio between the front chain ring and the rear sprocket. That ratio determines how far you travel with each revolution of the pedals. Mountain and hybrid bikes can have up to 27 gears using three chain rings and nine sprocket combinations. But some of these gears have ratios that are very similar, so each turn of the pedals propels you the same distance.
|11 (smallest and bottom)||28 (smallest)||1:2.55||68.7|
|15 (mid range)||38 (middle)||1:2.53||68.4|
|20 (couple from the top)||48 (largest)||1:2.4||64.8|
Three combinations of sprockets and chain rings give you basically the same “gear”
So why would you choose one over the others? Remember your straight chain? In this case, the middle option gives you the straightest chain. It also gives you more options for shifting up and down as your speed increases or decreases. And that’s what you want to achieve.
Knowing when to change the front rings is the key. These give you a sudden, large change in ratio, which can make pedalling too hard or too easy and you loose momentum quickly. Keeping your chain straight keeps you in closer touch with similar ratios and helps avoid those difficulties. Experiment and you’ll soon get the feel of it.
See you on the road soon, God willing. Eddie Barkla
First published in the Bendigo Weekly Friday 29 September 2006