First of all, I don’t generally have issues getting my shifting set-up correctly, but the front mech on my road bike seems to give me nothing but trouble.
I replaced the sq taper crankset with a Sora compact and it shifted OK, but always feels a bit like it’s only just working.
I bought a 48t chainring recently, fitted it tonight & went for a spin up & down the road to check the shifting. The mech won’t shift from large to small ring, so I’ve tried to sort it but can’t.
If I push the chain onto the inner ring and then shift back to the outer ring it always works. But it won’t drop back down again.
When the shifter is actuated, the mech moves but not enough to shove the chain far enough inwards. The cable is just slack and the limit screw has no more room to allow the mech to move in; it looks like the mech is on the limit of it’s movement and it’s still not enough. Even with the cable bolt loosened and the limit screw wound fully out, the chain won’t shift.
I also noticed that since changing to the 48t ring (from 50t) when the chain is on the smaller ring and I shift to the smaller sprockets on the cassette, the chain rubs the outer ring when any of the smallest 3 sprockets are used. It didn’t do this with the 50t ring.
It is almost like it needs a spacer in the BB on the drive side to push the rings outboard slightly. This would straighten the chainline slightly to stop this weird rubbing and also allow the front mech limit screw to actually be required for setting the inner limit position.
But, I am pretty sure that with a 68mm BB shell, the HTII BBs shouldn’t have any spacers fitted and the available axle length on the NDS does seem to concur with this.
There is a Shimano tech doc that mentions a 3mm spacer on the NDS of some Sora cranks, but this wouldn’t help with altering how far out the rings sit.
Thinking of just taking a 2.5mm spacer off my Inbred BB tomorrow and trying it to see if it helps, but don’t want to end up with not enough axle length on the NDS.
Any ideas much appreciated!