Getting into Gear

bikes parked in Cambridge

(2 min read)

Often, one of the most confusing things about riding a bike is the range of different gears bikes can have.

However, understanding gears doesn’t have to be difficult or stop you enjoying the fresh air and benefits of getting on your bike!


The cluster of sprockets on your rear wheel is known as a cassette. Depending on the type and age of your bike, it will probably have between 9 and 12 sprockets and will be referred to as 8-speed or 12-speed respectively. On a typical road bike, the smallest sprocket will typically have 11(11t) or 12 (12t) teeth and the largest 25 (25t) to 32 (32t) teeth.

Gear Ratios

If you are in your larger 50t chainring and your smallest 12t sprocket, what does this mean? This 50:12 gear ratio means that every turn of your pedals is multiplied by the gear to make your wheel rotate just over four times (50÷12=4.2). This gear is your “biggest gear”, it is the hardest to push but for each pedal rotation it will give you the greatest distance.

When you hit a hill, you will need to shift down to a lower or easier gear. On really steep slopes or if your legs are really tired, you might be in your lowest gear. This would be the smaller 34t chainring and the largest 28t sprocket. This 34:28 ratio would give you just over one rotation of your wheel for every pedal stroke (34÷28=1.2) and will hopefully get you up that tough hill.

Rear Mech

Your rear mech, also called a rear derailleur, shifts your chain between the sprockets on your cassette and is operated by your right-hand shifter.

front derailleur

Front Mech

Your front mech or front derailleur, shifts your chain between your chainring and is operated by your left-hand shifter. 

front derailleur


Attached to your cranks (the bits the pedals are on) are your chainrings. Most road bikes will have a double chainring set-up. Chainring sizes vary but a standard road set-up will typically have 53 teeth (53t) on the outer large chainring and 39 teeth (39t) on the smaller inner one. Compact gearing, with 50t on the outer and 34t on the inner, has become very popular for tackling hilly sportives and has largely replaced triple (three) chainring cranksets. Bikes with only one chainring on the front have fewer available gears, so will be more difficult on hills!

Cross Chaining

If you have your chain on the smaller chainring and smallest sprocket or larger chainring and largest sprocket, the angle of the chain will be fairly extreme. This is both inefficient and can result in premature component wear. With modern groupsets it is not such an issue as it used to be but should still be avoided where possible. 

Illustration by WickWerks
Illustration by WickWerks

Obviously, it is not vital to understand everything about the gears on your bike to have a good ride, but knowing the way gears work can help when choosing a bike and when you are clicking through the gears on a hill!


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 #cycling #gears #BikeWeek2019 


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