Sep 23 2014

Shifty Business: A Simple Fix for a Barrel Adjuster Gone Bad

Bar-end shifters are as versatile as they are convenient. My Shimano BS77 shifters are a case in point: The right-hand shifter — it moves the rear mech (derailleur) — offers you the choice of Indexed or Friction mode. Farwell prefers friction shifting. It’s quieter, for one thing, and it’s forgiving, too, freeing him from the nuisance of having to make fiddly adjustments as cables stretch and housings compress. So you can imagine his dismay when his friction shifters started acting up, “autoshifting” into higher gears on long climbs and fast sprints. He quickly ruled out all the usual suspects, i.e., a loose shifter, a frayed cable, a cracked end cap, or a slack clamp bolt. It was none of these. But the problem persisted. Then he thought to take a close look at the barrel adjuster on the down tube. And sure enough, he found that the right-hand adjuster was rotating under strain.

Once the problem had been isolated, the cause was easy to see: the detents on the plastic barrel had worn away, allowing the adjuster to move easily in response to cable tension. The cure? Replace the adjuster, of course. But Farwell is a stubborn guy, and he doesn’t like to spend money unnecessarily. So he tried a quick fix, instead, wedging a folded piece of paperboard (cut from a bumwad core; waste not, want not) between the adjuster and the down tube:

Cardboard Shim

Would that cure the trouble? It did. And Farwell marked the adjuster with an inked line to verify that it was staying put. But bumwad core, though admirable stuff in its place, isn’t exactly weatherproof, and Farwell started looking around for something better. He found it in our box of superannuated inner tubes. Folded inner-tube material proved to be the perfect shim:

Improved Barrel Adjuster Shim

When stretched, the wodge of rubber thins down, slipping easily into the tiny gap between adjuster and frame. Once the tension is released, however, it rebounds, locking the barrel in place. And rain won’t reduce it to a soggy paste. It works so well, in fact, that Farwell is putting his order for replacement adjusters on hold. If it ain’t broke, he says, why replace it?

Why, indeed?


Further Reading

 

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