Square Taper Cranks (A.K.A. Cotterless) vs. ISIS Cranks

Square Taper Cranks (A.K.A. Cotterless) vs. ISIS Cranks


A unicycle’s cranks attach to the hub axle and provide an attachment point for the pedals. Thereby, the crank arms serve as the interface between the rider and the unicycle.

Crank arms are made in different lengths, from different materials, and in different formats. For instance, there are square taper cranks (also known as cotterless cranks) as well as splined cranks, and a special type of splined crank known as an ISIS crank.

Although you can change your unicycle’s cranks to make them longer or shorter or to take advantage of a lighter or stronger crank material, you’ll still have to replace them with a set of crank arms that matches the hub configuration.

Here’s what you need to know about the differences between cotterless and ISIS cranks, as well as why you’d want to change them in the first place.

Why Change Your Cranks?

Besides aesthetics, there are a few practical reasons you might want to swap out your unicycle’s crank arms.

The length of the cranks will have a significant impact on how easily you can control the unicycle’s wheel and manage rotational momentum. It will also impact comfort.

For instance, the leverage of longer crankset arms is increased when compared to shorter cranks. Longer cranks will make it easier to start, stop or turn the unicycle, even though you will have to cover a greater total distance of rotation.

It’s harder to control a unicycle the shorter the crank arms are, but if you have sufficient strength, the shorter total circumference will make it easier for you to get up to speed more quickly. If you’re strong enough, the shorter total revolution might also result in a more agile unicycle.

Also, there is the matter of comfort. Even though a unicycle might technically be properly sized for a rider of a given height, longer cranksets might be difficult to reach at the bottom of rotation while making a rider feel bunched up at the top of the revolution. Similarly, for a taller rider, shorter cranks might feel unwieldy.

Ultimately, control and comfort are the two biggest reasons you’d want to change out your cranks.

What Are Square Taper Cranks?

                                   Square taper cranks

These are the simplest type of unicycle cranks on the market today and are common on beginner unicycles as well as on many affordable unicycles.

Square taper cranks can be recognized by their square opening that accepts the hub axle of the wheel. If you look at some of the cranks on our website, the ones that have a square hole are square taper cranks - ergo the name. You can also see this square interface when you take off the bolt securing the crank - if it’s a square, you have cotterless cranks.

Square taper cranks are pushed onto the square taper of the hub axle, which produces a tight friction fit, and then secured in place with a nut or bolt. They are affordable and relatively easy to produce, which makes them popular on some models of unicycles.

If your unicycle has square taper cranks, be aware that many models require a crank puller to remove and install them, so get one of these with a new set of cranks if you are uncertain or call us for more information.

Also, if you ever notice that your crank arms seem loose, never ride the unicycle. Either fix the fit, tighten the bolt that secures them or replace the crank arms entirely. Riding a unicycle that has loose cotterless cranks can round off the points of the hub axle’s square taper spindle, allowing the crank arm to rotate around the hub axle instead of turning it, permanently the unicycle.

What Are ISIS Cranks?

                                       Square taper cranks

In addition to square taper cranks, we also have a special type of splined cranks called ISIS cranks. Whereas cotterless cranks are square in cross-section, splined cranks have raised ridges or teeth, called “splines” that correspond to a splined hub axle on certain models. You can see these raised ridges when you remove the crank bolt or nut that secures the crank arms.

ISIS cranks are splined cranks that have sloped, rounded splines (if you look at them in cross-section, the raised edges that create the “peaks”of the splines are curved and concave. These types of cranks are common on higher-end unicycles, as well as mountain unicycles and other models that are intended to be ridden over rough terrain or see a bit of abuse.

Because there is more total surface area in contact between the crank and the hub axle, ISIS cranks (and other splined cranks) are significantly stronger than square taper cranks. However, like square taper cranks, if you’re planning on removing your ISIS cranks and installing a different size, you’ll need a crank extractor or you run the risk of damaging the axle threads.

One thing to note is that it is very important that you only ever install ISIS cranks on the appropriate side of the unicycle. Riding a unicycle with ISIS cranks installed on the wrong side (for instance, accidentally switching the right and left cranks) will permanently damage them.

Additionally, it is also important to routinely check the crank nuts that secure ISIS cranks and splined cranks as they can work loose over time. Always check them regularly as, just like with square taper cranks, you never want to ride a unicycle if the crank arms are not properly installed and tightly secured to the hub axle.

Additional Information and What You Need to Replace Your Cranks

In addition to ensuring that you’re buying the right type of cranks for your unicycle, you’ll also need to make sure that you’re getting a model with compatible threads. You can see that marked in each product listing, but if you’re unsure, refer to your unicycle’s manual or contact us directly.

                 Square taper cranks

You’ll also want a crank puller like our 2-in-1 Crank Puller that has ends for both square taper cranks and ISIS cranks and is perfect for loosening and removing tight crank arms. A torque wrench like our Pedal Wrench Socket Combo Tool is also ideal for removing axle bolts and removing and installing pedals. You can find both in our collection of unicycle tools.

                                                         Square taper cranks

Contact Us for More Information!

Need help determining what type of cranks your unicycle has, or more information on how to remove your current cranks and replace them with new ones? Get in touch with us at 678-494-4962 and let us know what you need.