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TCR gray barrel adjusters(6 posts)

TCR gray barrel adjustersdsweiss
Sep 22, 2002 9:23 AM
I'm putting together a TCR with Dura Ace shifters and my giant frame came with these 11/2 inch corrugated gray barrel adjusters and these two inch dumb bell shaped objects that I believe go over the cable in between the barrel adjuster and the shifters. I am having trouble understanding the principle behind these adjusters and I am not sure if I have the installation correct. Can someone save me a trip to the bike store and answer these 2 questions.
In line cable adjusters.Spoke Wrench
Sep 22, 2002 10:50 AM
I suspect that the dumb bells look like cable housing, right? So the shift cable runs through one of the dumb bells, then through the cable adjuster, then through the longer piece of cable housing and finally to the cable stop in the frame.

Turning the cable adjuster can either push the two pieces of cable housing apart which increases cable tension or allow them to come closer together which decreases cable tension.

Good luck.
In line cable adjusters.dsweiss
Sep 22, 2002 11:48 AM
Cool, thanks for the info on the setup. But I still don't understand how pushing the cable housing apart will increase the tension since the cable itself can move within the housing. In other words, the cable is not moving, so how does its tension increase? I'm just curious.
Technically, you're right.Spoke Wrench
Sep 22, 2002 1:07 PM
The tension doesn't really increase, the cable just pulls on whatever it's connected to.

When you push the two pieces of the cable housing apart, the cable has to go farther. Since one end is anchored on the shifter for example, the other end has to pull on the derailleur. That causes the derailleur to move a bit to make whatever fine adjustment is necessary.
Technically, you're right.dsweiss
Sep 22, 2002 1:56 PM
I see what you are saying. But both ends are anchored, not just the end at the shifter. I was thinking that perhaps, by increasing or decreasing the arc it essentially tugs on the cable, but does not actually pull on the wire directly. I'm still confused somewhat. It seems like that if the cable passes freely through the outer casing all the way from the shifter to the deraullier then changes in the length of the outer casing would not have an effect.
think of it this wayDougSloan
Sep 22, 2002 5:03 PM
Imagine an inner cable 50 inches long. Then, put it inside a cable housing 49 inches long. Now anchor both ends of the cable right at the ends of the housing. At that point, there is no tension on the cable, and no room for it to move, right? Now, without changing anything else, lengthen the housing by 1/2 inch. What happens? You are forcing the inner cable to stretch and putting tension on it, right? That's what's going on.

Doug