Ever heard of square taper cranks, AKA cotterless cranks? They are one of the more common types of cranks on the market, especially on beginner and budget cycles (including unicycles).
Basically, in the cotterless configuration, the bottom bracket has a cross-section that is a tapered square (hence the name). They are intuitive to install, allow more room for the bearing, and are very cost-effective to produce.
But there is one huge issue that plagues square taper cranks, and it’s the issue of rounding off, which can cripple the cranks and the whole machine. The damage is irreversible, but it is also relatively easy to avoid.
Here’s how to identify this issue of crank deformation and prevent it from happening to you again in the future.
Understanding and Preventing the Problem
The main issue here with rounded square taper cranks is actually one of loose bolts. If you do not install and torque the bolt to the tightness recommended by the manufacturer, eventually, the crank arms will work loose.
Even if you can’t feel it through the pedals, then the square taper cranks work loose, and there is play in them, they will get deformed. Specifically, what happens is that the sharp edges of the square cross-section round off, and what you end up with is a deformed-looking square.
Once this happens, even if you re-install the crank arms and then tighten down the bolt that secures them adequately, it’s only a matter of time before they work loose again. Then the cranks will continue to deform before you can’t use them at all.
When this happens, your only legitimate recourse is to replace the crankset entirely.
But if you do, remember, the only way to prevent this from happening is to make sure that your crank arms are installed properly and appropriately tightened before you ride. If they come loose while riding (as a result of loose bolts) they will get deformed.
One thing to keep in mind here is that rounded square taper cranks, though they can be caused by a variety of different things, are nearly always caused by insufficient torque being applied when installing. Rectifying this issue should prevent you from experiencing crankset deformation in the future.
Need a New Set of Square Taper Cranks for Your Ride?
If you’re looking for a new set of square taper cranks, you can get it online at Unicycle.com. They carry a wide range of crank arms, crank removal tools, and pedals, many of which are compatible with bikes as well as unicycles.
Another note: square taper cranks, though they are relatively easy to install and cost-effective, are widely considered inferior to ISIS cranks (also known as splined cranks). If you’re having a problem with your square taper crank unicycle, consider getting one that accepts splined cranks. They are more durable and can handle more torquing power without sustaining damage, making them better for more rigorous riding, such as Muni riding.
