Small or Big Chainring

Small or Big Chainring

When cycling with a double or triple chainring, it's always useful to ask yourself which chainring to choose.

Indeed, riding between 25 and 30 km/h on flat terrain can be done with different gear ratios. Here's an example with a 34, 39, and 50 teeth chainring (thus covering the use of a compact chainset):

On the road, it's indeed the same whether you use one gear ratio or another, except that one chainring is more suitable than the others. Assuming that it's very important to pedal at the same speed and that changing gear ratios too often is tiring, let's adapt our way of using gear ratios. The solution lies on the cassette side.

Spacing of the cassette

Nowadays, bike cassettes come with 8 to 10 gears, and sometimes even 11. How are these gears spaced to go from 13 teeth to 25 teeth?

Take a look at your bike, there's a good chance that the smaller gears are spaced by 1 tooth (13, 14, 15, 16, 17) and then by 2 teeth (19, 21, 23, 25) like in this Shimano 9-speed cassette from 13 to 25 teeth.
So what's the best chainring for flat terrain?

Best chainring for flat terrain

The best chainring for flat terrain is the one that allows us to stay within the range of gears that are spaced by 1 tooth. With the 50-tooth chainring, going from 21 to 23 results in a difference in speed of more than 2.5 km/h.

From 15 to 17 with the 39-tooth chainring, we have 3 gears spaced by 1 tooth with just a 2 km/h difference for each tooth.

With this chainring on gears spaced by 1 tooth, the pedaling rhythm can be maintained without too much change, which is better for the cyclist.