Which chainring do i need

Measuring procedure will be explained in chapters below. The dimension that we need is from centre to centre. However, I find it hard to measure that accurately, so I measure from end to end, using vernier calipers, as shown in picture 2 it gives the same dimension, just using a different method. It takes measuring the distance of two adjacent bolts, then multiplying it by 1.

Table 1 gives a list of standard sizes of 5 bolt mounted chainring BCD-s. All the sizes are given in millimetres divide with Both methods are shown in picture 4.

Table 2 gives a list of standard sizes of 4 bolt mounted chainring BCD-s. Newer chainsets are 4 bolt while everything else is 5 bolt. BCD is different between compact and standard chainrings.

Compacts use a smaller BCD — usually mm — which allows them to use rings with fewer teeth. Standard cranks have a larger BCD — usually mm — which limits the smaller chainring that fits on them to a 38 tooth. It also means you can go up to 55 teeth on the outer. Shimano recently made the BCD the same on their newest compact and standard cranks. This allows more sizes of chainrings to be used, making it handy for swapping to lower gears if needed.

Handily, BCD is usually cleared displayed on chainrings. So have a look at your existing chainring if you need clarification. As well as getting the correct spider and BCD, you need to check which brand the chainring is compatible with ie. Shimano, Campagnolo or Sram. They are all a bit different. Single ring cranks must use a dedicated single ring. Single chainrings are available in sizes from 38T upwards.

Standard double cranks — the most common combination is 39 tooth inner and 53 tooth outer. A good quality chainring allows you to be energy efficient when cycling. The materials used in the construction of the chainring are important, as they need to withstand the stresses that result from repeated pedalling. Aluminium and steel are the most popular choices due to the good ratio of strength, weight and cost of the materials.

Carbon and titanium are two more unusual materials that can also be used in the production of chainrings. Many chainrings feature shifting ramps or pins. They are usually featured on the middle and outer chainrings on triple chainsets. It's time to replace chainrings when the teeth become hooked in appearance and the gear shifting is not as crisp as it should be.