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.
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.
170mm
This is a more popular size. 170mm cranks provide a good balance between leverage and control.
175mm
Just a small step up from 170mm. If you are not too picky. This is a good size for you.
180mm
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.
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.
Tips
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.
Check Out My e-book
Kindle Version
PDF Version
Writing this book was a huge goal for me. I spent a lot of time creating these 60 pages of goodness. In this book, I talk about how specs can influence your riding. For example…
Did you know how a short chain stay can make spins easier? Or how the reach of a stem can make bars or whips harder?. Check out the book to brush up on your bmx knowledge.
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.
