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Chainring count - the number of chainrings on the chainset. Fixed gear track bikes, single-speeds and some geared bikes use a single chainring, road bikes commonly use a double (two rings) and most touring bikes and mountain bikes will use a triple chainset (three rings).

Tooth count - the number of teeth on the chainring(s), the higher the number the harder the gear.

Chain width - this is only relevant for chainsets with a single chainring - if this is ⅛” then you must use a ⅛” chain. All double and triple (and some single) ring chainsets will use a standard 3/32” chain.

BCD - stands for Bolt Circle Diameter (sometimes referred to as PCD - Pitch Circle Diameter) and is only really needed when changing chainrings. To calculate the BCD, measure the distance in millimeters from the centre of any chainring bolt to the centre of an adjacent one and multiply it by 1.709 (you’ll likely need to round the resulting number up or down a little to get your BCD measurement).

*Intended speed - the number of cogs at the back the chainset was designed to be used with. We refer to it as ‘intended’ speed as most double and triple chainsets will actually work with different speeds than originally intended, but the further away you get from the intended speed the more likely you are to experience minor setup issues. The exception being some chainsets intended for 10 speed use or higher, with these it’s better to stick to the intended speed.

Crank length - this is measured from the absolute centre of the bottom bracket hole to the centre of the hole for the pedal.

Pedal threads - the pattern of the thread that your pedals screw into, this is usually stamped on the pedals themselves and most bikes use a standard thread of 9/16” x 20 tpi. The exceptions being older French bikes, bikes with cheaper one-piece type chainsets and Shimano’s Dyna Drive system (easily identifiable as the pedal holes are about an inch wide!).

Bottom bracket type - ‘square taper’, as the name suggests have a square shaped axle that slots into the chainset and ‘cottered’ axles are round and secured by pins - pretty much every bike up until the 1990s would use one of these, cottered being the much earlier system. Since then, different manufacturers have introduced their own systems that are not interchangeable so you must use a chainset that matches.

Chainring count - the number of chainrings on the chainset. Fixed gear track bikes, single-speeds and some geared bikes use a single chainring, road bikes commonly use a double (two rings) and most touring bikes and mountain bikes will use a triple chainset (three rings).

Tooth count - the number of teeth on the chainring(s), the higher the number the harder the gear.

Chain width - this is only relevant for chainsets with a single chainring - if this is ⅛” then you must use a ⅛” chain. All double and triple (and some single) ring chainsets will use a standard 3/32” chain.

BCD - stands for Bolt Circle Diameter (sometimes referred to as PCD - Pitch Circle Diameter) and is only really needed when changing chainrings. To calculate the BCD, measure the distance in millimeters from the centre of any chainring bolt to the centre of an adjacent one and multiply it by 1.709 (you’ll likely need to round the resulting number up or down a little to get your BCD measurement).

*Intended speed - the number of cogs at the back the chainset was designed to be used with. We refer to it as ‘intended’ speed as most double and triple chainsets will actually work with different speeds than originally intended, but the further away you get from the intended speed the more likely you are to experience minor setup issues. The exception being some chainsets intended for 10 speed use or higher, with these it’s better to stick to the intended speed.

Crank length - this is measured from the absolute centre of the bottom bracket hole to the centre of the hole for the pedal.

Pedal threads - the pattern of the thread that your pedals screw into, this is usually stamped on the pedals themselves and most bikes use a standard thread of 9/16” x 20 tpi. The exceptions being older French bikes, bikes with cheaper one-piece type chainsets and Shimano’s Dyna Drive system (easily identifiable as the pedal holes are about an inch wide!).

Bottom bracket type - ‘square taper’, as the name suggests have a square shaped axle that slots into the chainset and ‘cottered’ axles are round and secured by pins - pretty much every bike up until the 1990s would use one of these, cottered being the much earlier system. Since then, different manufacturers have introduced their own systems that are not interchangeable so you must use a chainset that matches.