Wednesday, December 01, 2010

Chain Tube

When I built my bike I used cheap and available PVC pipe for a chain tube. I wanted something long enough to protect my chain from dirt flying up from the front tire, and rigid enough to alleviate the need for a guide pulley on the lower run of the chain. Since then, I've decided that the PVC tube is too noisy, especially since installing a larger freewheel. The biggest problem with rigid chain tubes is alignment. The tube has to have enough float to keep itself aligned with wherever the chain is going to or coming from while not sliding forward or back.

A trip to the local True Value Hardware store yielded 4 feet of clear vinyl tubing intended for use in RV water systems. At $.69 per foot, I couldn't go wrong. It was pretty curled up, but some hot water made it pliable enough to stretch out. There is still a little curve, but the tubing is soft enough that I don't think it's anything to worry about. As soon as the chain has tension, the tubing straightens out.

For the lower run, I used zip ties to grip (but not squeeze) the tube at the top of the fork. There is some float there, but the tube can't slide back with the chain. I cut this section long enough to pass a couple inches aft of the tire, then placed another pair of zip ties near the back end to hold the tube away from the tire.

For a while, I had a second PVC pipe on the upper run below the seat, to keep the chain from rubbing on the original wide tire I had. When I put the skinnier tire on, I omitted the top tube since it was noisy and (I thought) not needed. Well, things being what they are, I went with putting a piece of this quite and flexible stuff back there to keep the chain cleaner. Since I'm using the bike for commuting, I need all the help I can keeping the chain clean.

I'm pretty happy with the results, just spinning the chain through by hand in the garage. The tubes move around where they need, and the clicking and scraping of the chain running through the rigid tube has been reduced to a very soft "thubbing" noise. I can't wait to take it out for another ride.

The Dia-Compe front brake works much better than the previous versions. The action felt worlds better when I took a 17 mile ride on Sunday. Even in the blasted, cursed, nearly freezing, sent straight from hell, jacket drenching, shiver causing rain, the front brake felt better. Some new pads are in order, though.



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