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How To Choose The Right Cog For Your Bike

The cog choice for your bike will be depending on several factors, such as the way you intend to use the bike, the cassette size and a good development, depending on how many teeth your chainring has.

What’s a bike cog, and how does it work?


Bicycle cogs are installed onto the rear wheel hub or axle.

The cog on the bike is responsible for transmitting the energy applied to the pedals to the rear wheels. In short, they let the wheel turn and advance when you pedal.

Smaller sprockets are distinguished by a longer and faster cadence, while larger ones have mean a slower, shorter cadence. The latter are especially useful for climbing ramps or sloping roads.

Choosing a bike cog is a crucial task for the bike to work properly. When selecting it you must consider the number of teeth it has.

Difference between a fixed sprocket and a freewheel


  • Fixed

The main feature of a fixed sprocket is that you must never stop pedalling. If you don't, the bike stops. To brake properly you must slow down or keep the pedals in a fixed position, even skidding.

Power transmission is direct and for this reason it is the type of gear used in track cycling. It is widely used in the city, as it does not usually break down due to its simple operation.

  • Freewheel

Freewheels on the other hand are different. When you stop pedalling, the wheel continues to turn without transmitting the energy or inertia of the pedalling movement. You can have a single sprocket (singlespeed), or multiple gears, by means of a cassette.

It is possible to switch from a fixed-gear to a freewheel bike. Changing a bike from freewheel to fixed gear is a simple process. You just have to remove the wheel and mount it again on the other side if it has a flip-flop hub.

Differences between a cassette, a freewheel and a singlespeed cog


A cassette is a piece that can include several chainrings or sprockets, held together by rivets or screws. WIth a singlespeed cog, however, only one piece will be attached to the hub.

The cassette acts as an axle, and its sprockets work “inside” its hub. Cogs are attached to the exterior of it.

The number of teeth that can be found on a cassette will vary depending on the smallest and biggest sprocket sizes. The more teeth a cog has, the easier it is to make the wheel spin.

The cog works together with the chainring, the chain and a tensioning cable that pressures and helps move the chain so that you can change gears.

A freewheel, on the other hand, works differently. Athough it is formed by different cogs and chainrings as well, each of them with a different number of teeth, it is screwed to the wheel axle thanks to a set of matching indentations.

Cog types


Regarding cog typology, the following can be found:

  • Coaster brake

Coaster-brake-hub cogs come with different speeds and with a varying number of teeth.

Coaster brakes are made up by a hub on the bike’s rear wheel and spins freely. Manufacturers such as Sturmey Archer and WG stand out.

  • Fixed

Fixed sprockets should be used by cyclists with previous experience, as they require a little more effort and ability to be used. This is because the bike can never be neutral if such a hub is equipped on it

They are more efficient, as they transmit pedalling energy directly to the wheel. They are very common on track bikes. Those by Ridea and WG are amongst the most sold ones.

  • Freewheel (singlespeed)

Freewheel, singlespeed bikes let the wheel axle to spin in a direction while the chainring may be spinning in reverse. With them, you can stop pedaling and the wheel won’t stop moving or get blocked.

Freewheel cogs are used on virtually any kind of bike, and amongst the most standing ones are those by Dnp Inc and WG.

  • Freewheel

Freewheel performance will vary depending on the teeth on each cog. It can be used to change the transmission development of the bike. Brands such as Epoch and Sunrace are some of the most renowned ones.

  • Cassettes

A cassette is a set of cogs put together, and must be screwed to the rear wheel hub. Epoch and Shimano are amongst the best-known brands.

The kind of cassette to use will depend on how the bike is used. For instance, current road bikes normally have a cassette with 9, 10 or 11 cogs (and speeds).

  • Lockring

A lockring is a component that ensures that the fixed-gear cog is tightly attached to the hub, and it prevents its thread to be stropped. It’s placed on the bike wheel’s axle and tends to be made of stainless steel. BLB and Menjoin are good brand choices.

Number of teeth


Cogs can also be classified according to the number of teeth they have, ranging from 12 up to 22.

Keep in mind that the more cogs and/or teeth, the more versatile the bike gears will be, and it will be easier to find the right cadence for many different grounds.

Tools for cog maintenance


To ensure your bike is always on point and working properly, it’s advisable to take care of its cogs, and to do so it’s good to have several tools at hand, that will let you install an uninstall cogs with ease in case it’s time to change them.

Using a key to extract the cog, degreasers to clean and lubricants to grease up this part of the bike are the essentials.

Only if cogs are clean, lubricated and in a perfect condition will they ease a good functioning of the bike’s transmission, and energy won’t be lost while pedaling. Riding will be nicer, and keeping them in good shape is a key to enjoying your bike to the fullest.