I've been having some bike issues with a 2016 Trek Allant 7.4 . I'm looking for any documentation about this problem, or any known solutions that don't include externally routing the cable.
Long story short is that the gears aren't shifting properly. I've seen it up on the mechanic's stand and within a few minutes he was able to downshift on the shifter and the derailleur didn't budge at all.
When I ride you have to downshift one past the gear you want and then upshift again to reliably get it into gear.
If you downshift a few gears at once, like you might when going up a hill, downshifting one more than you need and then up again doesn't always seem to get you into the gear that's selected on the shifter.
What happens then is that the derailleur changes the gears at some unexpected time to the gear that is actually selected on the shifter. There's a crunch that I'm sure isn't great for the cassette or the chain, and your weight gets thrown off balance.
The mechanic I spoke to said that this was a problem with the design of the Allant 7.4. The shifter cable comes out straight at the same angle from the chain stay. It gets bent upward and sits in contact with the quick release nut. The mechanic told me that the problem was due to the sharpness of the angle that the cable was routed after it exited the chain stay.
The same mechanic told me that this problem was addressed in later models. I've attached a photo of the Allant 7.4 and FX-4 routing and you can see that the FX-4 angles the cable upward at the exit from the chain stay. It looks like the FX-4 routing is along a much more gentle curve as well.
The shop I bought the bike from has replaced every single component involved in the rear gears (possibly not the external sheath at the back? The manager told me this couldn't be the cause of the problem). The cassette, derailleur, chain, shifters, shifter cable core (now using a thinner core) have all been replaced.
The bike has been looked at by 5 mechanics: 3 mechanics from the store that retailed the bike and stock only Trek bicycles, and 2 mechanics who are Trek employees.
This experience has really put me off internally routed cabling and Trek bikes in general to be completely honest.
Does anyone know of any documentation around this issue? Are there any known fixes?