Wednesday, November 19, 2008

For a while now I've been needing to change my headset. The headset of a bike is the bearing mechanism that allows you to turn the handlebars, thus steering. This was my first bike repair that one of my books says is best left to experts. You could take that as a warning, but I guess I took it as a challenge.

First I took the front brakes off of the fork:

I loosened the stem and pulled it (along with the handlebars) out. There's Seth helping in the background:

Next I loosened the locknut. That's it at the top:

Once I got the locknut, washer and cup and bearings off of the top I was able to pull the fork off through the bottom. Here it is dropped down a little bit. You can see the bearings in their retainer with some very gunky grease (the grease should be a lot cleaner):

Once I got the fork out and wiped the grease out of the cups that are attached to the frame, I flipped the bike upside down so that I could inspect the bottom cup. Here it is, and you can see what the problem with this old headset is. That black stuff is pitting. The ball bearings get caught up in that when I go to make a turn.

Those old cups have to go to make way for my new headset. The cups are pressed into the frame with a tool called a cup-press, which cost around $150 and looks something like this:

And are removed with a tool called a rocket which costs around $30 and looks like this:

After doing some online research, I decided that I could make both of these tools for about $5 apiece. Here is how I made the rocket. I got a foot long, 7/8 inch copper repair coupling at the local hardware store. I used a marker, ruler, adjustable wrench and my table top to mark where I wanted to cut it:

Then I secured it n my bike repair stand (since I don't have a bench vise) and used a hacksaw to cut it. I chose a blade with 32 teeth per inch, since the coupling has pretty thin walls (and you want at least three teeth in contact with the surface you're cutting at a time).

The rocket gets inserted through the head tube:

and pulled up until it snaps into place:

Now you start to hammer on it:

It took a good deal of hammering, but finally the cup came flying out.

Then I flipped the bike over and did it to the other cup.

Next I had to press the new cups in. I made my own press. It was much easier to make than the rocket. I bought a foot long piece of 3/4 inch threaded steal rod, with two nuts and six washers. I also got a piece of suede from a craft store. I cut the suede to match the size and shape of the washers:

Here is the finished press:

First I pressed the bottom cup in:

Then the top cone. The press worked beautifully. I measured their fit with a caliper before pressing them in. They are supposed to be a bout 0.1 to 0.2 mm larger than the headtube that they are being pressed into, but they were about 0.5 mm bigger. I was worried that I might run into trouble (and really I probably should have had the headtube reamed, but I didn't want to bother with that), but it pressing them in went smoothly.

Next I had one more piece to remove: the crown race, which is the bearing cone that sits at the crown of the fork. I couldn't get mine off, so I took it to a bike shop. The guy there managed to get it off and then asked for the new one to put it on. That's where I made my mistake. I didn't measure the crown race and the steerer tube on which it sits. As the guy pounded it on, we realized too late that the steerer tube was too small. The crown race cracked:

So now I will have to get a new crown race. Get someone to take off the cracked one, machine down the steerer tube and put on the new race. Oh bother I hoped to get back on my bike today.

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