Admittedly, I don’t often work on flatbar setups, so this one has left me somewhat intrigued. A long time client recently dropped off his daughter’s bike, a Trek Marlin, set up with Shimano Altus all round. One of the issues she had been dealing with was chain drops at both ends (inside/outside).
Resolving the issue of the chain dropping on the inside (onto the BB) was easily sorted out with a slight adjustment to the limit screw. It’s the chain dropping on the outside that has gotten me befuddled.
The shifter is specifically, an M315-2L variant, while the FD is an M315-TS, both designed for 2x chainrings. On closer inspection, the shifter is an exact replica of the M315-L 3x variant, without the “3” printed onto the optical display. I’ve found that you could actually shift past the “2” on the M315-2L shifter into what should theoretically be the “3” position. In doing so, the FD actually shifts the chain off the big ring, leading to chain drops. This leads me to the suspicion that that was what my client’s daughter has been doing - overshifting, so that the derailleur moves a little too far outboard, causing the chain to fall off.
Is this normal for the M315 2x setups? I’ve resorted to some degree of finessing the “H” limit screw so that it prevents the FD from moving into the vacant “3” position, but outboard enough so that shifting from the small chainring to the big one is still pretty straightforward.
Keen to hear thoughts/experiences.
Thanks all!
