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I have a Shimano Alfine 8 hub. I am aware of the need to keep an eye on the shift cable tension, and readjust periodically to ensure that the alignment marks on the hub are lined up.

The strange thing is, over time (on the order of a couple of months or so) the cable tension seems to increase.

On other cable-actuated components (brakes on this bike, brakes, shifters on other bikes I've owned), the cable tension tends to loosen. Cable stretch and, on brakes, pad wear lead to a need to tighten up the cable a bit now and then, before eventually something needs replacing (whether the cable or brake pads or both).

Why on this installation, would I keep finding that the cable tension needs to be loosened periodically?

Is there some other explanation other than that I somehow am accidentally brushing up against the adjustment knob and routinely increasing tension, which then needs to be backed off periodically?

  • Could it be vibration turning the barrel adjusters slowly over time? Is there a chance theres a piece of cable housing no set properly in the frames cable mounts? I had an Alfine 11 for a few months. I remember all the "fun" of trying to get it and keep it dialed in. – l008com Oct 29 '18 at 4:08
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    Speculating a little, but check the tightness and condition of the drive side axle hardware (the cone and locknut and the things between them) and make sure the cassette joint is properly installed. I can see this happening on an Alfine 8 hub if the part of the cassette joint that stops the cable were able to slip clockwise due to the washer-like thing on the hub it engages being damaged or loose, while the other part of the cassette joint stays stationary with the driver, or something like that. – Nathan Knutson Oct 29 '18 at 4:10
  • Check for dirt filling the groove the cable runs in at the hub interface (that shift actuation mech that fits on the hub). As it is an arc, the diameter will get slightly wider, increasing the effective cable tension as dirt fills the groove. – Rider_X Oct 29 '18 at 5:13
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    Could somebody (children?) be playing with the adjusters? Not that I haven't seen this happening. – Carel Oct 29 '18 at 15:47
  • Good suggestions to look at. No children are messing with it. I can't rule out that someone is fiddling with it while the bike's parked at work during the day, but I think it's really unlikely. I'll go over the cable route again, but I think @Nathan's suggestion to check for slippage in the hub itself has the most promise. I guess first step there is to just take a look and see if it looks like the hub components have rotated from their expected position. – Peter Duniho Oct 30 '18 at 3:30
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I'll note even some potential problem causes that might sound stupid, but in my experience, even a quaified mechanic can sometimes make a mistake, and not take something trivial into consideration, so not wanting to insult anyone's intelligence by stating some "stupid", or "I obviously checked that" potential problems, it is what it is: a simple troubleshooting list of the top of my head, based on the previous experience:

Numbers 2) and 5) are what I'd first suspect. But I woul check everything, especially when there is a problem.

1) Is the hub assembled properly, with all the parts in place?

2) Is the wheel fixed properly within the dropouts - no movement? Geared hubs have special washers that prevent the hub from turning even slightly - if these are not seated and tightened properly, a small, one degree hub rotation of the hub (under chain tension when pedalling) could increase the cable tension). That, with most other stuff is nicely explained here: Sheldon Brown's page about geared hub setup and maintenance.

3) Are the bars and the shifter lever fixed properly?

4) Housing used should be for shifters, not brake housing - brake housing changes a bit more in legth as the cable running through it changes tension. (pictures and explanation of the shifter/brake housing differences)

5) If the shifter cable passes beneath the bottom bracket, it should pass through a guide, not along the metal of the frame's bottom - if it doesn't, flexing of the frame can move the cable sideways, changing its tension.

Bottom bracket cable guide

6) Routing the housing should be done properly - making it as short as possible, but without too many total direction change (extreme example is making a full circle, even with a gradual radius - it will create a lot of friction and setting up the cable tension would be difficult, as well as shifter operation).

7) Frayed cable, or dirty/damaged housing might cause the cable to stick.

8) Are you accidentally moving the cable adjuster? :) Some have a locknut, most don't. A simple marker could be a way to see if it's been moved over time. Movement from road vibes is not likely, since the barrels usually have to overcome the barrel spring tension in order to be moved over small "grooves" - most have that sort of mechanism. Even if they don't, bolts tend to loosen through road vibes - moving towards lower tension, which in this case would mean barrel adjuster turning inwards, loosening cable tension over time.

  • Thanks...the above is all very useful, even though I've already checked most of the points you mention. It's not a friction issue (the misalignment is still there even when shifting up, increasing tension), and the setup hasn't changed in the eight years I've had the bike (i.e. part selection, cable routing and the hub washers, both of which I've double-checked already, etc.). I can't honestly say it's answered the question per se, but there are a couple of things above I haven't ruled out yet, so that remains to be seen. – Peter Duniho Nov 1 '18 at 16:13

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