Crank Connection Question

Hello Everyone,

I have a 24" Red Torker in Arizona that has 150 cranks. I want to change the cranks to 125s, but the connection on the red uni with the 150s looks different than all of my other unis, which are all cotterless and almost all Torkers.

The red Torker with the 150 cranks look like cotterless, but the connection seems to look more like ISIS (I don’t have any ISIS unicycles, so I really don’t what they look like up close).

The picture on the right is the connection on the 150 cranks that I want to replace with 125s.
The picture on the left is the type of crank connection on all of my other Torkers, etc.

I am traveling via train to Arizona from Louisiana for a week hoping to switch the cranks to 125s when I get there. I was going to do that the last time I went, but decided against it when I discovered the strange connection. I don’t want to attempt to change the cranks and then discover I don’t have the right tools or equipment, etc. I would much prefer to ride on 125s, but I would rather ride 150s than nothing.

Thanks in advance for your suggestions and advice.

Thanks Everyone! :slight_smile:

you need an 8mm allen key for the isis bolt (M8) on the right. The good news is that you can pull out that bolt and put it back in without any worry that you’re going to hurt anything.

Pulling ISIS cranks using a crank puller requires you to have an ISIS specific crank puller (it has an additional attachment that doesn’t ruin the threads on the inside of the hub) see: it has an additional (and removable) foot on the end. If you don’t have access to an ISIS crank puller, you can also use a coin and a standard crank puller if you’re careful. when you get the crank off, just drop a coin over the hole that the bolt went in before using the crank puller, so it will push against the coin instead of falling in the ISIS bolt hole.

If you don’t own a crank puller, you can also pull out the M8 bolt, and wiggle the cranks (carefully) until they start to loosen. This isn’t recommended, but it will do in a pinch if you’re careful about it and the cranks aren’t too too tight.

Installing the crank arms back is very easy. Get your left and right correct, slip them on, and tighten up the M8 ISIS bolt.

Not all square-taper hubs use external nuts to secure the cranks. Some are internally threaded and use the same bolts as ISIS hubs. You’ll need to remove the bolt to see which kind it is.

If you have the right type of cranks but not the tools, you could take it to a bike shop to have them change the cranks. That’s what I did on a trip to San Diego. I think they charged $5. We also rented a bike so he might have given me a deal on the crank installation.

Most ST cranks on bikes use bolts which look like those on the right to secure the cranks. That looks like a ST crank to me, but you don’t need to take that bolt off to see - just look at the back side of the crank where it attaches to the axle, there should be an obvious square or splined section (you might need to drop the wheel out to see, but that’s a simple operation).

That’s right in the case of square tapers. For ISIS cranks, though, the splines are often (most of the time?) covered by crank spacers, so it’s not obvious. That’s how it is on mine, anyway.

The only point I was trying to make in the earlier post was that I have owned square-taper hubs that were internally-threaded for crank bolts, just like the ISIS hubs, so you can’t always tell what kind of hub it is just by looking at the bolt. (Although an external nut means square taper every time.)

Hello again Everyone!

I had no doubt you would provide excellent help! I have lots of tools, but no ISIS crank puller. I will order one just in case, and I will review all of this info again before packing my tools and cranks.

Thanks so much Everyone!!!

If it is square tapered and has an 8mm crank bolt, I’m assuming you still have to use an ISIS-style crank puller (or a coin over the hole), correct?

I haven’t seen square tapered with the M8 bolt before. I just assumed it was ISIS. Interesting. Sorry if anything I said above was misleading.

Nope. Square taper with bolts was standard practice on better bikes (with Campagnolo, decent Shimano, etc., parts) for decades, the canonical arrangement that the pullers were designed for. I use a small flat washer, for 1/4" screws IIRC, when pulling ISIS cranks btw.

I’ve had more with screws than nuts but maybe that’s a function of the sample I’ve happened to see. My commuter bike (converted rigid steel mountain bike) has nuts while my other tandem unicycles all use screws–although hex head more often than Allen. Nuts seem more common on down-market gear.

On the thrift-shop Sun unicycle that had the floppy crank arms when I got it, the connection had failed by stretching at the base of the threaded stubs, and that looks to be in intrinsic weak spot of the arrangement. I guess it must be some fraction of a cent cheaper making them that way.

As LargeEddie said in response to juggleaddict below, you don’t need an ISIS crank puller.
I’ve tried removing a square taper crank once using an ISIS puller …realized I was using the wrong puller as I was torquing down super hard on the wrench but it wouldn’t loosen…

Ah, good point. I hadn’t really thought properly about ISIS hubs - though in a way the point stands, if you can see a square section at the back it’s ST, if there is just a spacer behind the hub then it’s ISIS. The difference should also be obvious from the spindle diameter.

Personally I don’t own an ISIS puller, just standard ones - I have a special insert for use with ISIS, but have also used coins. As mentioned above an ISIS puller will likely get jammed in the ST interface if used with a ST hub which takes bolts rather than nuts. I’ve had lots of ST axles on bikes, and the only one I’ve ever seen which took nuts was on my cheap beginner uni - checking UDC, the ones they sell all take bolts.

Thanks everyone!
It was much easier than I was expecting!
In fact, it was lots easier than changing a regular cotterless crank.
Why don’t they make them all like that?!
Thanks again everyone…including Alucard.

:smiley: :smiley: :smiley: :smiley: :smiley: :smiley:

Went looking for pictures but couldn’t find any… :stuck_out_tongue:

Out of interest, what sort of hub did it have?


Hey there James.
I posted comparison pictures in the question at the top.
Can you see those?