Everything you need to know about gear ratios

What are gear ratios?

Gear ratios affect how the bike will accelerate and what top speed you can achieve.
Put in its simplest form there are three types of gear ratio: 1) hard, 2) medium and 3) soft.

Hard - Slow acceleration but high to speed.

Medium - Inbetween/average acceleration and top speed.

Soft - Fast acceleration but slow top speed.

How do we measure gear ratios?

Simply divide the number of teeth on your front cog (sprocket) by the number of teeth on your rear cog.

What gear ratio is best for me?

Well it really depends on your style of riding.  If you are an out and out street rider that likes to hit everything at full pelt then a harder gear rattio is your best choice, however if you are more of a tech rider or prefer slower variations of moves then a easier gear ratio is your best choice.

Gear ratio chart

The convental and most popular gear ratio is 2.75 for BMX and this is the sort of area you should ideally be aiming for but as stated above you may want to have a harder or softer gear ratio than this dependiong on your style and type of riding.

Gear Ratio Chart

23

24/29:9

28:10

30:11

33/34:12

36:13

38/39:14

41/42:15

44:16

46/47:17

49/50:18

NB: This chart is based upon 2.75 being the gear ratio, for personal preference add or take away one tooth at a time from either side to work out gear ratios best suited for other styles and types of riding.

NB: There are many other gear ratios other than the ones above, this is purely an example and it is not writen law that the 2.75 gear ratio must be standard, in BMX anything goes and dont let others tell you otherwise.

Is there anything else other than the cogs sizzes that affect gear ratios?

Yes there are. The length on the cranks you use will create different leverage ratios.  For example two riders use the same size cogs, 25 on the front and 9 on the rear but rider a has 165mm cranks and rider b has 175mm cranks.  Rider a will have a harder gear ratio than rider b because longer crank arms create a higher leverage ratio than shorter crank arms..  There are factors that affect gear ratios like wheel size and tyre size but they do not have a very significant effect on the gear ratio.