At a basic level, a sprocket is a toothed wheel whose teeth interlock with the chain drive to transfer power from the engine to the rear wheel via a chain.

So far, everything seems simple. But sprockets come in all sizes – some are bigger than others, which begs the question: “Does size matter?” 

And the short answer is, “yes, it does.” 

In this blog post, you’ll discover more about motorcycle sprocket sizes, such as:

  • What determines the size of a sprocket
  • How to calculate your “sprocket ratio”
  • How performance is affected – just by switching to a smaller or bigger sized sprocket

Motorcycle Sprocket Sizes Explained

image of motorcycle sprocket

The key thing to remember about sprocket sizes is that the size is NOT determined by its diameter – instead, the size is determined by the number of teeth it has.

The more teeth, the bigger the sprocket. 

And the good news is that if you want to, you can change the front or rear sprocket with something bigger. 

There’s even a term for it – and fittingly, that term is “sprocketing.”

What about sprocket ratios?

Much like gear ratios, “sprocket ratio” refers to the difference in size between the two sprockets.

And the sprocket ratio formula is simple –  divide the number of teeth on the front sprocket by the number of teeth on the rear sprocket.

Let’s say that we have a bike with a front sprocket with a total of 20 teeth and a rear sprocket with 60 teeth.

In that case, the sprocket ratio equals 1:3 since 20/60 = 0.3.

“But where do I find the front sprocket?”

Good question – although the rear sprocket is clearly out in the open on bikes with chain drive, the front sprocket isn’t as easy to find.

But you can find and indeed replace it. It’s usually found on the output shaft of the transmission housing.  

To get to it,  you need to remove the cover for your transmission or your front sprocket. In some cases, you might have to loosen your rear wheel.

There you go – there’s your front sprocket!

What Does a Bigger Sprocket Do On a Motorcycle?

It depends on several things – the primary factor is whether the bigger sprocket is at the front or rear.

Is the bigger sprocket at the front? 

Then you can expect an increased top speed at the expense of worsened acceleration.

On the flip side, if the bigger sprocket is at the rear, you’ll have faster acceleration, although your top speed (not to mention your fuel efficiency) will suffer.

One final thing – replacing a smaller sprocket for a bigger one is NOT the be-all-end-all – there are other factors to consider, such as chain size and chain pitch.