what are splinned hubs? (And cranks)

Hi, I never started a thred before, but I have a question so here it goes.
I have an old shwinn 24 inch that I had for a long time since I was a teenager, and I just started to ride it again after not riding it for a few years.
I’m thinking about getting a new unicycle and I keep hearing about these splinned cranks and hubs.
I know that they are supposed to be stronger, but how much stronger are they? Does it make a big difference?
Also, does any one know how thay are constructed?
Thank you.
It’s nice to see all the unicyclists out there on the internet.:slight_smile:

the search function is your friend. and on the profile and onza websites i think they discuss this.

But type “splined” not “splinned”.

Klaas Bil

The difference between “splined” and “tapered” is to do with how the crank is attached to the hub.

On a normal square tapered hub, the ends of the axle (spindle) have square prejections which poke into square sockets cast in the ends of the cranks. The crank is then held in place with a nut (or, in some cases, a bolt). The advantages: it’s cheap, easy, and does the job. The disadvantages: they can work loose. The force fo the pedaling is concentrated on the edges of the square taper, and this can result in wear and tear.

On a splined hub, the end of the axle (spindle) is shaped like a cog, with lots of teeth (or “splines”). The crank is shaped to fit these splines. This is more expensive, harder to make, abut spreads the load better, making for a stronger and more durable set up.


Yo Homie it’s like this. There be 3 major types of crank to axle interfaces: Cottered, Square Taper, and splizined.


I’ll let my man Sheldon Brown Handle this one:

The axles and crank holes are round. The axles have a groove in them. A wedge, called a cotter, slips in there to keep the crank still.

The cotters are thin little pieces of metal that taper. They wear out and have to be replaced. Sometimes they shear in half and bad times. Don’t get those.

Square Taper:



This was the standard in the bike industry for many years and is still the standard in the unicycle industry. Many bikes still use this as well. The axle is a square peice of metal that tapers (thinner on the outside). This allows you to press a crank (which has the same taper on the inside) on to the axle by using a bolt. This system is reasonably strong. Problems exist in the maintenance. The cranks cannot be removed very often, since each installation removes material from the axle. This will eventually wear down your axle. On bikes it screws up your chainline. Also, if someone rides on a loose crank, the axle and crank turn into round useless things never to be useful again. If installed properly the first time, this is a good system.




A more recent development in the bike industry and even moreso in unicycles, splined axles are totally the way of the future dude. They’re like mega awesome. The axle has grooves on it. The inside of the crank has a matching pattern (although different companies make different patterns, because unicyclists are dumb and don’t use ISIS yet) and they slide together all nice like. It’s great, thats all you need to know. Buy some. And then bitch that they aren’t ISIS.

That was a great description from Obie! But it leaves one question for me now… what’s ISIS, and what separates it from other types?

Cotterless is still the standard for the majority of the bicycle industry, and all it needs. But bikes don’t put as much wear & tear on the crank/axle interface, so they don’t need an improvement. Splined parts are used on bikes that get more punishment, such as high-end BMX, Trials and mountain bikes. Those take a lot more pounding, though it might be argued that our constant back-and-forth torque puts even more strain on unicycle axles.

Thanks. I got a new idea a while back. We see the same questions every week or two, so why not answer them once fairly well and then just copy everything the next time we see the question?

ISIS is the new standard in bicycle splined bottom brackets. All ISIS components are interchangeable, since all ISIS bb’s are the same diameter and flute pattern. Same with cranks. So if you’ve got a bike, you can use a truvative bb and raceface cranks etc.

This would be great for unicycles, since right now each hub has about 3 crank lengths. Also, this would allow use of many many different cranks already available to the bike industry. One potential problem is that ISIS spindles have a much larger diameter than is used on unicycles. However, this also means extra strength.

Right. Unicycles put a ton more stress on axles, since whenever we do anything we are basically putting stress downward on both cranks, which makes the axle want to twist. This causes a lot of sheared and deformed axles. On bikes, the axle floats freely in bearings, so the stresses aren’t nearly as bad. My mod has a square taper axle, and many do for weight considerations, since they hold up as long as the cranks are installed properly and you don’t switch them out very much.

I created a new forum for this purpose. Feel free to add your “repost” in there as an article.

Perfect. Good job, I’ll clean it up a little and add some stuff, then put it there. One potential problem is that the article section is going to be used for quite some time, so IMG tags could become broken, which means everything in there should probably be attachments.