BMX Specs: Crank Length

Recently I was shopping for cranks, and I saw a few different sizes. I could buy anywhere from a 160mm to a 180mm. Does 20mm really make a difference? Let's look into what the different crank sizes do to your riding.

bmx crank length explained

The main thing with crank length is the distance from one end to another. Some riders like really short cranks and some like the feeling of longer cranks. There isn't really a huge difference, but there is enough to make a difference.

Brant Moore does a good job explaining this in the video above.

Different Size Options

Here are the main crank arm sizes that I have seen:

  • 160mm
  • 170mm
  • 175mm
  • 180mm

160 mm

160mm cranks are usually the shortest cranks available for a 20" bike. They do not make it easier to pedal since there is less leverage. People ride 160mm cranks so pedals are closer to center and therefore are easier to catch when whipping.


This is a more popular size. 170mm cranks provide a good balance between leverage and control.


Just a small step up from 170mm. If you are not too picky. This is a good size for you.


Definitely the longest crank arm that I have seen. Usually, trail riders love this size so that they can get extra leverage and pedal easier.

what crank arm length is best for you?

Does it really matter?

I don't think that the length really matters that much, to be honest. When I was 15 or so, at Woodward. I cracked a crank arm and Jake Kinney had an extra one that he let me use. It was a 180mm and I had a 170. However, I just put the crank on and eventually, I got used to it.


If you hit your foot on your tires or pegs when you pedal get shorter cranks. This will move your pedal close to the center of the bike.

If you have a hard time pedaling, and want to go faster.. Get longer cranks.

Crank Splines

I'm going to add a quick edit in here since I forgot to mention the difference in crank splines. Most low-level bikes come with 8 spline cranks, while aftermarket cranks are 48 spline. 48 spline is a lot more expensive but also stronger. Upgrading to 48 spline was the best thing I've done.

48 spline

These are the strongest spline option available. With 48 splines, the cranks act like they are almost connected, which makes them so much stronger. By using this method, they are also able to hollow out the spindle making the cranks lighter.

8 spline

8 spline cranks are most commonly noticed by the pinch bolt that keeps the cranks from falling off or feeling loose. 8 spline cranks are heavier and weaker for a number of reasons. But mostly due to the fact that they are made to a lower standard with weaker materials.

Favorite Cranks

Still confused?

Reach out on Instagram, and I'll help you find the perfect crank arms.

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