Maintenance / Repair Videos

Better Cable Shifting
by Fastolfe
Post on BROL on 7/1/12

Here is some great info on cable routing for better shfting that was posted on Bentrideronline. I thought it was so good that i wanted to post it. This the copy of the post but youcan read the whole thread here BROL CABLE THREADING

I'll let you in on a little secret: all derailleurs / shifters work more or less equally reliably, and need no adjustments once set properly. 99% of the time, the culprit for finicky derailleurs that hesitate, that never quite line up properly with the sprockets each time, or have trouble dropping to the smallest sprockets, or coming back up if you readjust them to reach said sprockets, is either the cable or the housing (most likely both), or the cable's routing.

Here are the recipes for proper, crisp shifting for any derailleur:

- Work hard on your cable routing: determine the route that'll let the cable take as wide and gentle turns as possible. Always choose a longer path with an extra gentle loop that lets the cable enter the shifter, derailleur or frame bosses perpendicularly, rather than a shorter route with a kink at the end of the housing. If you do have a kink and can't work around it, make sure the rest of the cable's route is extra-smooth. And no, your bike's manufacturer may not have chosen the most optimal route for the cables on their own bikes, so don't trust their choice of routing.

- Choose extra-wide shifter housing: Usually the outside diameter of that sort of housing is the same as that of brake housing, and the inside diameter is slightly larger than the recommended norm. It's also stiffer, which will tell you quickly if you're trying to get it to bend too tightly

- Once you've determined the ideal route, cut the ends of the housing with good quality pliers, then (and that's a big, big part of getting derailleurs and shifters to work crisply), gently bend the housing manually until it naturally assumes roughly the shape it'll have on the bike. Then look at the ends of the housing: if you have bends near the ends, you should see individual metal strands stick out more on the inside of the bend. That is, the cut you made with the pliers now looks slanted. That's what causes lack of precision in shifting. To avoid that, grind the ends of the housing very flat and as perpendicular to the cable as possible, with the cable bent to its final shape. Use a grinder or the face of a Dremel cutting wheel, but do it slowly to avoid overheating the housing's outer sleeve and inner teflon guide.

- Use a thumbtack to enlarge the teflon inner at the ends of the housing.

- Install the housing on the bike, without the cable. Use properly fitting metal ferrules. If you have to use zip ties, don't tighten them too hard, to allow the housing to move a bit and to avoid crushing it (yes, it can crush enough to create a friction point).

- Never EVER use black teflon-coated cables: these work great for a while, then they quickly become stickier than regular, good quality uncoated steel cables.

- Uncoil the cable VERY GENTLY so it doesn't get any kink in it. If it does get a kink, even a slight one, and you can't work it away with your fingers, throw the cable away. Yes, really, it's ruined.

- Install the cable slowly. If you did your routing right, the cable end should be able to poke out of the housing and enter a boss or the derailleur without you helping it, or very nearly so.

- Replace your housings and cables as soon as the shifting becomes less than perfect. Don't assume the derailleur or the shifter need readjusting, it's just the cable. On an open bike in clement weather, it should occur every year or so.

Do all that and I can guarantee you perfect shifting with any shifter/mech.

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