Why Do So Many Unicycles Use Square Taper Cranks?

You may have read, experienced, or even heard from a seasoned rider that ISIS cranks (or splined cranks in general) offer a superior fit than square taper cranks. If that’s the case, then, all else being equal, why do so many unicycles have square taper cranks?

There is some truth to the previous statement about the quality, durability, and dependability of ISIS cranks, but that doesn’t mean square taper cranksets are “bad.” To illustrate this, let’s take a step back.

Square taper cranksets, which are also known as cotterless cranks, are a fairly common type of crankset paired with modern unicycles, specifically beginner and affordable unicycles.

Hub axles that accept cotterless cranks are tapered inward and square in cross-section. The ends of the crank arms are tapered and also square in section; the user must force these into the hub axle where they will provide a friction fit that is secured via the aid of a nut or crank bolt.

They may seem basic and straightforward, but affixing them can be intuitive and when secured properly, they deliver a perfectly serviceable interface between the crank arms and hub axle.

Affordability and Production
Now let’s offer a word on why square taper (cotterless) cranks remain so popular when it would seem like superior alternatives are available. It largely comes down to two main factors. Ease of production and affordability.

The manufacturing process for producing cotterless cranks is much simpler than that for producing splined cranks like ISIS cranks. As a result, it is more affordable to produce square taper cranksets and they can be produced more efficiently as well.

Considering the fact that some riders - such as beginner and casual riders - simply don’t have the need for the durability of splined cranks, cotterless cranks are perfectly reasonable.

Naturally, the fact that it costs less for manufacturers to produce these types of cranksets also helps to keep the overall price of a finished unicycle down. The lower the overall cost of input, the lower the cost of the finished machine - and that holds true for unicycles. Many affordable unicycles are made with square taper cranks for that very reason.

It ultimately comes down to ease of production and affordability, which makes unicycles with these types of cranksets not only popular among beginners, but also appropriate.

Why You Should Never Ride with Loose Square Taper Cranks
Now that it’s clear that so many manufacturers choose to use square taper cranks for their affordability and ease of production, there is one caveat we should offer. You should never, under any conditions, attempt to ride a unicycle with cotterless cranks unless they are properly affixed and secured. Doing so could permanently damage the unicycle. What’s worse, if you ever ride with loose cotterless cranks, you could damage not only the crankset, but also the hub axle.

Here’s what you need to know. Square taper cranksets fit into a hub axle that is also square in cross-section. All the bolt that secures them does is ensure there is no play between the crankset and the hub axle.

Because it is square in cross-section, the cranks are not able to rotate in the hub axle; instead, angular rotation causes the hub axle and thus the wheel to rotate. This results in an enormous amount of force transferred between the crank arms and the hub axle - particularly concentrated at the corners of the “square” that forms the joint between them.

If you ever ride a unicycle that has cotterless cranks and the cranksets are not properly secured or tightened within the hub axle, the force generated by pedaling can and will likely deform the interface, either rounding out the crankset or distorting the hub axle. If this happens, it will make it impossible for the cranksets ever to be properly fitted and tightened again - causing permanent damage.

This can be prevented, however, by riding only when the cranksets are properly tightened. Check them before you ride and tighten them if need be.

Are There Better Alternatives to Square Taper Cranks?
With all of that said, there are other types of cranksets - namely splined cranksets like ISIS cranks, that provide a more secure fit and greater durability than cotterless cranks.

As opposed to the square cross section of cotterless cranks, ISIS cranks are “splined” which means they have additional “teeth” that slip into a hub axle that is approximately star shaped in cross section. Because friction is a product of surface area and there is a greater surface area interface between the crankset and hub axle, splined cranks like ISIS cranks provide a better fit than cotterless cranks and are much more durable.

Because they provide such a secure fit, ISIS cranks are preferred by some riders, especially street, trials and mountain unicycle riders. These cranksets are better able to transfer power and stand up better to hard use, impact and the higher torque needed to control and maneuver unicycles when performing tricks, clearing obstacles or negotiating unpredictable terrain.

One thing you should be aware of when swapping out or maintaining ISIS cranks: while they are not susceptible to the exact same drawbacks of cotterless cranks, you must make sure you always install them on the proper side. Riding a unicycle with ISIS cranks switched (that is, with the left crankset installed on the right hub axle and vice versa) could permanently damage them.

Contact Us to Learn More!
Looking for more information on changing out cranksets, or which unicycle you should choose to pursue a given discipline? We can help with both, and in addition to our square taper cranks, we also carry replacement cranksets, pedals, and necessary tools like torque wrenches, pedal wrenches and crank pullers for removing and installing cranks. Check out our Unicycle FAQs for more information on crank arm length, the different types of unicycles, and more. If you need additional help, just get in touch with us directly.

You can reach us via the live chat at the bottom of this screen, but if you need immediate help, you can give us a call at 678-494-4962.