Shimano 7 Speed Cassette

I have an old 21 speed hybrid bicycle. I was keeping my daughter company while she was out running at Rood Ridge Park a couple of weeks ago and the chain broke. It was an old bike and it hadn't seen much use lately. My younger son has taken an interest in bicycles lately, so I thought I would show him how to replace the chain.

Whenever you buy a new chain for a bike with a derailleur, you should replace the high speed sprocket (the smallest one) on the rear axle, as it tends to get the most wear (being the smallest). When it gets worn it likes to slip, which is annoying, and it also causes the chain to wear faster. I had a new sprocket and I bought a new chain and we set to work. Got the wheel off. Now to remove the special nut that holds the sprockets on. This requires a special wrench, but the wrench will only go into the recess about one sixteenth of an inch, and it will not hold. Try as I might I cannot get it to hold. Whenever I put pressure on it, it jumps out. Finally conclude that the wrench must be too worn to work, even though it has not been used more than half a dozen times. I am not sure what the deal is here. It has been a while, like five or ten years, since I did any work on my bikes, but I don't remember it being this difficult. Perhaps I didn't work on this one, perhaps it was my other bike and though it also has a seven cog cassette, perhaps it is made differently.

So today I went and bought a new wrench. I was afraid it was going to be $25 or so, but it was only $8. The local Bike 'N Hike had a whole selection of them, and more importantly, a guy who could tell which one I needed. Brought the new wrench home and attacked the sprockets once more. No better. What is going on? It now looks like it is not engaging even a sixteenth of an inch, it looks more like a thirty-second. Do we have to pull the axle out?!?!?! No other option at this point, so out it comes, and naturally the ball bearings start falling out on the floor. What a nuisance. But look! The wrench slides way in now, engaging perhaps a quarter of an inch. No problem now getting the old sprockets off. Check things out, put it back together. Do we have all the balls for the bearings? Pull the tool chest away from the wall to recover one errant one but that is all. Hmmm, we might be missing one. Put it back together anyway. Does not feel like there is one missing. We shall see.

Adjusting the bearing cones is a trick. There is a big rubber seal on one side that is blocking access to the cone. Deal with this by putting the wrench on the cone first and then tightening the lock nut with its' attendant seal. Once the bearing are adjusted and the lock nuts tightened, we can pull the cone wrench out, and seal seals up the hole.

Putting the chain on was a snap, literally. Used to be you needed a pin press to work with chains. This chain has a two piece master link that simply clicks together. The hardest part was threading the chain through the derailleur and then holding the two ends together while I installed the master link. Took it for a test ride and everything seems to be working okay. Except the handlebars, but that is going to have to wait for another time.