Square Tapered Crank Removal

Square tapered cranks have existed for a long time, and the vast majority of bikes used to use them. Many still do, and I can show you how to remove them in case you need to service the bottom bracket or replace a chainring or whatever. First you need a crank puller, you really can't remove a crank without one (well technically you can, but you won't be able to reuse it..). You will also need a tool to remove the crank bolts, and these are usually on pretty tight so you'll want something with leverage. Crank bolts are usually 14mm hex or 8mm Allen bolts, and I've even seen 15mm hex ones too. That's about it as far as tools are concerned. Let's get started:

First pry out or unscrew any dustcaps covering the crank bolt:

Remove the bolt (or nut in this case). I have a pedal wrench with a 14 and 15mm socket attachment on it that I like to use for these, otherwise a ratchet with the correct sized socket works nice. Once you remove the bolt you will see the bottom bracket spindle and the square hole around it:

Now it's time to use the crank puller. First you thread the puller all the way in so that it's engaging as many threads as possible. Start by hand to avoid cross threading it, then use a wrench to turn the puller all the way in. Don't tighten it once it's done, just leave it snug. Next you will turn the puller's handle to force the crank off. There will be lots of resistance at first, but once it gets easy to turn you can slide the crank off.

 

Here is a type of crank puller without a handle. You use it the same way as the Park Tool puller shown above, but you need to put a wrench on the top part. I like these since you can put a ratchet on it and just turn it without worrying about the pedal interfering.

Here is the bare spindle after the crank was pulled off:

I like to clean the flat parts of the spindle and put a very thin layer of grease on them so that the crank slides back on correctly (grease is optional). To reinstall the crank you just shove it onto the spindle, then tighten the crank bolt to push the crank onto the taper. You need to turn the bolt a lot at first, even after you start to feel resistance because the crank has to be pushed back into place by the bolt.

Don't leave the bolt loose. I think the torque spec is at least 25 ft-lbs which is pretty substantial for a bike part. If it's too loose the crank will get rounded out as you pedal, so make sure that bolt is very tight. After all that you're done. You should never retighten crank bolts if they were tightened properly the first time. This tutorial is also useful for splined cranks like Octalink or ISIS, you'll just need a wider attachment for your crank puller.