If you remove a pair of square taper cranks from a unicycle, you will see that the interface between the cranks and the bottom bracket axle is square in cross section. This is where the name comes from, though they are also called cotterless cranks. 

The corners of the square engage the bottom bracket axle (spindle) and transfer leverage that way, so when you rotate the crank arms, the wheel spins. It’s simply enough.

They’re not just found on unicycles. You can find them on bikes as well, but as far as unicycles are concerned, they’re fairly common on affordable and especially beginner models. 

The reason for this has primarily to do with the economy of the setup. It’s relatively cost-effective to produce square taper cranks, but on top of that, square taper bottom brackets also tend to be fairly durable and can even have bigger bearings. 

But, while they are common on beginner unicycles and do just fine for most riders, assuming they are installed correctly and properly tightened, there is one very important note about making sure that the crankset bolts are properly fastened.

What Happens If You Install Them Improperly or Ride with Them Loose?

In contrast to square taper cranks, splined cranks, which have more surface area contact between the bottom bracket and the crank taper, are much more robust overall. 

As a result, if you install square taper cranks and they’re loose in the bottom bracket, when you go to turn the crankset, the corners of the crankset can round off in the bottom bracket, or get otherwise deformed. 

When this happens, the crankset will no longer be able to properly engage the bottom bracket. The end result is that you can no longer crank the wheel using the pedals. 

It also indicates irreversible damage to the crankset that will require them to be replaced, and in some instances, the damage might be even more severe than that. 

Fortunately, the fix is prevention, and it’s easy prevention at that. Simply make sure that your square taper cranks are properly installed in the bottom bracket before riding, and more importantly make sure that the crank arms are properly fastened and that there is no play in them.

If your unicycle (or bike) has square taper cranks, make sure you check the crank arms before you ride, every time. An ounce of prevention is better than a pound of treatment. 

Need a New Pair of Square Taper Cranks?

Sometimes, if the crankset gets damaged, all you need to do is replace the crank arms. If that’s the case, you just need a place where you can get a new pair. 

Check out Unicycle.com first. They carry a wide range of unicycle parts, tools and accessories, including crank arms and pedals, among other essentials. And, for what it’s worth, and despite the name, they carry a lot of bike parts and tools as well. 

Visit their website and get in touch with them directly if you need assistance before you buy anything.

For more information about Clown Circus Bike and Knee Elbow and Wrist Pads Please visit: Unicycle.com.