How to Install or Replace Crank Cotters

Disclaimer: I am not a professional bicycle mechanic. This post describes my experiences only, and should not be used as a definitive guide. You should consult other sources or visit a professional mechanic before attempting anything described here.

Here's the follow-up to my post a few days ago about removing crank cotters. If you're lucky enough to be able to reuse the old cotters (i.e., if you've removed the cranks only to access the bottom bracket), this process is much easier than if you need to replace the pins themselves, as was my situation.

First, some fundamentals about how cottered cranks work. As I mentioned in my post on removing cotters, the crank axle of a bicycle with cottered cranks has a flat notch cut on either side. This flat contacts the angled flat of the cotter pin, and this is what keeps the crank arms 180 degrees apart. You can see in the photo below that with the crank arms removed, the notches on either side of the axle face away from each other.

When you put the crank arms on the axle, you can see more clearly how the pin is supposed to fit.

In the image above, the pedal end of the crank arm is to the left, and is pointing toward the front of the bicycle. On the other side of the bicycle, the crank arm is pointing the opposite direction, toward the rear of the bicycle. Just to be perfectly clear, this is how it should look:

In the picture above, the bike is upside-down, but this is just for ease of photographing. Obviously, removal and installation of cotters is best done when the bike is upright, since the crank arms need to be supported while hammering.

If you can reuse the old cotters, all you need to do now is reverse the process of removing them. When you place the pin in its hole, make sure the flat of the pin contacts the flat of the axle. Then, with the crank arm supported with a block of wood or length of pipe, use a hammer to pound the pin from the smooth (non-threaded) end. Strike it just as hard as you had to when you removed the pin, as you'll be wedging the pin tightly into its spot. Just like removing them, one or two hard whacks should do it.

Once enough of the threaded end has emerged from the other side, put the nut on and tighten it with your fingers. Take another couple of whacks on the smooth side, just to seat the pin a bit more, and see if you can tighten the nut again with just your fingers. Repeat until the pin won't go any farther in, then tighten the nut down tight with a wrench. Repeat the process on the other side, but double-check as you work that the crank arms remain 180 degrees apart.

If you need to replace the crank cotters, all of this is complicated by the fact that the flat side on most new stock replacement cotters will need to be filed down in order to fit correctly against the crank axle. Many new pins are simply cut from a soft metal rod of more-or-less the correct diameter, then the flat is pressed into them, rather than machined to the correct angle. Even if the flat is machined, it is often way off from what it should be. I used a 6" general purpose mill file (single cut bastard), which removes metal more gradually and precisely than a double-cut file.

Ideally, you can use the shape of the old pin as a guide for filing the new one. The idea is to preserve the angle, but file it down so that it will fit your axle. This can be tricky, as you need to keep the file flat against the pin, but apply slightly more pressure to the down side of the angle. Sheldon Brown probably says it better. The photo below shows two new pins, the one on the left has been filed to fit my axle, the one on the right is how the pins arrived. This shows how much you may need to file to get the correct angle.

As you work on the filing, keep trying the pin in the crank so see how it's fitting against the flat of the axle. I found it helpful to support both crank arms with pieces of wood to make sure they were staying 180 degrees apart. That way, all I had to do was drop the pin into the hole to see if I needed to file the flat down any more. This took a lot of time, as I was proceeding cautiously, not wanting to take too much off, or ruin the angle of the pin. Sheldon Brown suggests using a bench-mounted vise to hold the pin in order to ensure that you're filing at the correct angle, but I have neither a vise, nor a bench to mount it on, so I held the pin with a pair of pliers wrapped in electrical tape (so as not to damage the pin with the teeth).

Eventually, I was able to file the angle of the pin down enough so that the threaded end of the pin was just poking out the other side of the crank arm. I lubed the pin with light oil to make it easier to drive, then gave it a couple of good whacks to drive it in. I actually had to do this several times, as the pin simply wouldn't drive far enough to get the nut threaded on. If this happens, it's no big deal. Just flip the crank over, drive the pin back out, do some more filing, and try again.

After a lot of trial and error, I was able to drive the pin far enough through that I could tighten the nut. Again, get it finger-tight, then give it a couple more whacks, tighten the nut again, give it a couple more whacks, etc., just to make sure it's seated as far as it will go, then tighten with a wrench. And again, keep checking as you work that the crank arms are still 180 degrees apart.

If you've filed the first pin correctly, it's easier to judge how much you need to file the second pin, since you'll already have one crank that is now fixed to the axle and not going anywhere. Sheldon Brown recommends replacing pins in pairs to preserve the 180 degree orientation of the cranks, but I was fortunate enough to be able to reuse my one good old pin, since I apparently did such a stellar job of filing the first one (how that happened, I don't know!).

Here's a few helpful things to keep in mind: 1) buy extra replacement cotters in case you mangle one of them trying to get it to fit; 2) the pins should be driven from opposite sides to maintain the 180 degree crank orientation; in other words, when the crank arms are parallel to the ground, the smooth head of the pin should be facing up on one side, and the threaded or nut-side of the pin on the other side should be facing up; 3) clean your file regularly as you work to prevent build-up of metal dust; 4) lube the pins before installation; 5) don't over-tighten the nuts, as this risks stripping the threads. The angled pin, driven tight against the axle is what keeps the crank attached, not the nuts. In other words, the nuts don't keep the pins from falling out, they just keep them from jiggling loose over time; 6) after a few dozen miles, repeat the process of hammering the pin and tightening the nut, as the pins will "settle" with use.

Finally, let me say that this was my first time doing this particular repair, and most of what I've said above comes from my reading of Sheldon Brown's guide. The idea in presenting my experience is not to claim it as definitive, but to 1) show that it can be done, even by a doofus like me; and 2) to try to give a bit more detail from one specific experience to supplement Sheldon's more general admonitions and advice.

PS--Glory of glories, you can now once again buy cotter pin presses, which were discontinued by Park Tools in the late 90s, from BikeSmith Design and Fabrication, which is where I got my replacement cotters. The presses are a little pricey at $55, but I imagine they're worth it, since they eliminate the hammering from this operation. I haven't used one myself, so this is not an endorsement or recommendation, just a heads-up.

How to Remove Crank Cotters

Disclaimer: I am not a professional bicycle mechanic. This account of my experience is intended for entertainment purposes only (woohoo!), and should not be considered the advice of a professional. In other words, I'm not responsible if you bungle the job!

That being said, let me say (as commenters RB and Giuseppe assured me), that this was not hard at all! Guys, you were right, it was probably the easiest thing I've done on this bike.

Sheldon Brown, God bless him, can sometimes make things sound much harder than they are. Based on Sheldon's guide, I was certain that I would mush the cotter pin, ruin my crank, and undo all of my good work on the Runwell. While doing the job correctly is important, it is not as hard as some internet bicycle gurus make it sound. That being said, Sheldon's word on the subject is still the standard, and it helped me a great deal.

You need only three things for this job: 1) a block of wood (I used a scrap of 1" x 8" board) cut to fit under the crank arm to support the arm when you hit the cotter pin; 2) a claw hammer (I padded mine with a small piece of rubber cut from an old tube in case I missed the pin and whacked the frame); and 3) some penetrating oil to lubricate the pin. You can also

use a piece of soft metal pipe (like copper) instead of a piece of wood, placed under the pin, but I doubt if most folks happen to have a piece of pipe in the correct length just laying about--I sure didn't. I also cut a piece of thin cardboard to protect the bottom bracket if I swung wild, but it proved unecessary.

Here's the setup:

I applied the penetrating oil liberally directly onto the pin a few days before I made the attempt, since I was a little apprehensive and wanted to give myself the best chance of success. Remove the nut and washer on the cotter to access the point where the wedge of the pin meets the flat of the crank axle inside the crank arm and apply the oil directly.

Once the oil has had a chance to work, you're ready to begin. Brace the crank arm on the wood block so that the threaded end of the cotter is pointing up, since this is the end you will strike with the hammer to drive the pin out. Needless to say (I hope), the nut and washer should be removed before you go at the pin with the hammer. With the crank arm braced and the washer and nut removed, all that's left is to whack that little bugger. Strike the pin a hard blow squarely with the hammer--imagine you're trying to drive a nail in just one whack. Grip the hammer as far away from the head as possible, like any good carpenter, since this will help deliver a more powerful blow. Here's what happened after just one strike:

I then tapped the pin gently all the way out, using a little screwdriver as a tap. And that's that. The other side was just the same; one strike and the pin was loose enough to just tap out. No damage to the cotters, the axle, the frame, or the bottom bracket in the process. In fact, unless you're some sort of hulking brute, it's unlikely that whacking the pin will do any sort of damage whatsoever. That's easy for me to say now that I've accomplished it, but this had been a point of some concern. Here are the pins after extraction; the one on the right is the damaged one that was causing my clunk (you can see the stripped threads):

Here's a bit about how cottered cranks work. The pin goes through the crank arm and that flat side gets wedged tight against the flat side of the crank axle (see below).

The flat of the pin contacting the flat of the axle is what turns the crank when you pedal, and the nut is just there to keep everything snug.

I'll say more about the mechanics of the whole operation and have some better photos when I install the new cotters in a few days (when they arrive in the mail). Hopefully that will go as smoothly as this did. I sound all confident now, but I was quite nervous when I started. Just goes to show that the things you worry about the most usually end up turning out the best (and the things you didn't think to worry about knock you on your arse).

An Old Bike Project is Never "Finished"

Looks like I spoke too soon. After riding the Runwell around a bit, it has developed a loud clunk in the right crank arm, the result of a mangled crank cotter that I just can't get tight enough anymore. Fortunately, I can order new cotters in the right size from Harris Cyclery, but it puts the bike out of commission for another week, at least, and forces me to confront yet another somewhat-dreaded DIY repair. I'd like to hear from anyone who has extracted/installed their own crank cotters without a cotter pin press. I've heard about bent pins, ruined cranks, etc., but I'd like to hear some happy stories with good endings. Anybody?

Surprise! Reassembly!

I had planned on doing the second clear coat today, and even started on it, but the first piece I coated (the front fender) got all bubbly and cracked and spotty-looking. I think I must have put on a too-heavy coat, but I decided not to push my luck with the other parts. So, instead of doing two coats of clear coat on everything, I'm calling it good with just one. Tomorrow, I'll buff off the botched clear coat on the front fender and then try to reapply it more smoothly. I put a coat of Turtle Wax on everything else, which will also act a protecting layer. Then, I took off the masking tape from the bearing cups and head badge and started putting the whole thing back together. As you can see below, I got the fork and handlebars, the seat, and the crank put back on the frame.

Nothing too technical here. I just put the seat back on so I could flip the bike over later to work on the crank, fenders, chain, etc.

Here's how I put the fork and stem on: 1) pack the bottom bearings of the fork and set on the bottom bearing race; 2) insert the fork into the tube and let the frame rest on the fork; 3) grease the bolt and expansion wedge on the stem and pack the top headset bearings; 4) insert the stem into the tube and tighten the stem bolt.

Tips on the process: 1) don't tighten the bearing races too much, just enough to hold the bearings in the cups. If you tighten the races too hard, they won't turn freely; 2) same goes for the stem bolt; it should be tight, but not so tight that it affects the steering of the bike; 3) try to line up the fork and handlebars with each other and with the frame; you can fine-tune once the bike is ridable, but the straighter everything is now, the easier it will be to make fine adjustments later.

And then, the crank. Pretty straight-forward: pack the bearings and grease the cups, lightly tighten the bearing race on the left (non-chain) side, and put the hardware back on. Again, when you tighten the nut on the outside of the left side, don't make it too tight, as this will push the bearing race into the bearings and affect the turning of the crank. Remember, the nuts and the bearing race on the crank turn counter-clockwise so they won't spin off while you're riding, so they don't have to be made too tight.

So, there you go--clear as mud, right?

Huffy/Raleigh Bottom Bracket

My Park Tools HCW-5 spanner came in over the weekend, and I immediately opened up the bottom bracket and found this waiting inside. What the hell is that stuff? Once again, I've posted a few more photos at my Flickr photostream.

I also found that the left side bearing race on the crank axle is badly pitted, although the bearings themselves and the adjustable cone seem to be fine. This isn't terrible news, since the left side cotter pin notch on the axle was also terribly worn and mangled, and I have an eBay-find replacement axle coming in the mail that should work (watch, now that I've said that, it won't fit!).

On a side note--it's always good to have the right tool for the job. I'd tried loosening the lock ring on the bottom bracket by tapping with a hammer and screwdriver (carefully), but no go. I was expecting a struggle to get the ring off, but I barely had to put any pressure on the spanner at all before it came loose. Just goes to show that a good tool is never a bad investment (minds out of the gutter, people!).

Cleaning Small Parts is Fun

So, I tackled the crank hardware last night and this morning using "Pedro's Bio Cleaner" (my usual all-purpose bike cleaner), a toothbrush, my thumbnail, and some very fine ("0000") steel wool. I used the toothbrush and my thumbnail to get the old dried-on grease off, and the steel wool to polish off the accumulated grime on the crank and crank arms, and to give them a bit of a shine. Compare the second photo with the similar "before" picture from yesterday.

My next goal is to take off the headset/fork. Should get to that in a day or two. At that point, everything will be off the frame and I'll be ready for cleaning, sanding, masking, priming, painting, detailing, and clear coating, all in that order. All done by me.

The Crank

I finally went to the hardware store and bought a big enough wrench to take off the crank. For future reference, I needed the 10" adjustable wrench for the 1 1/8" inch nut.

The photo on top is the "before" picture of the crank assembly. In this photo, the bike is upside down and we're looking at the left side crank.

The second photo shows the "exploded" assembly after I took it apart, with the bearings exposed. The bearings come out, too, but were left in for the picture. One note here: everything I've read on removing the crank says that a spanner wrench is needed to remove the bearing race (a.k.a., adjusting cone), but mine came off just by turning with my fingers. Is this bad? I don't know.

In the third and fourth photos, I've circled the groove in the threads and the little tooth on the crank plate and washer than fits into it. These should be lined up for reassembly.

The fifth photo shows how dirty and grimy the inside of the crank assembly was. Shown here are the bearings for the right side. The old bearing grease has dried up and gotten gummy and dirty, which was probably dramatically affecting the ride of the bicycle. The last photo shows what fell out of the inside of the crank assembly--one very greasy, very dead insect.

Once I clean things up, I'll post some new pictures, just for contrast. I also have some thoughts on painting to post soon.