I have an old Sora 3303 with triple configuration in front. I had to replace the middle chainring due to wear, but there are no Shimano parts available, so I bought this:
https://www.chainreactioncycles.com/.../rp-prod175961
I changed the chainring, and everything seemed to fit fine. I can also shift fine from inner to middle chainring.
But the issue is that it is almost impossible to shift from middle to big chainring. The chain kind of "gets stuck" between the gears/chainring and will not shift to the big chainring. It does not seem to be due to the derailleur adjustment itself, there is "enough room" on the H-limit to do the shift. I have also tried to move the derailleur farther/closer to the large chainring - with no difference.
Any ideas?
* Can it be that the chainring has been mounted wrong way? I think I put it the same way as the old one with regards to the small pins. But just to confirm: I guess the helping pins should be facing towards the small chainring?
* Can it be that the outer dimension on the chainring is different than the old one? Even of the number of teeth are the same? If the dimension is different, I guess there can be some issues with the built-in "track" in the derailleur cage that normally helps shifting to the big ring?
* Can it be chainring orientation? There were no markings on the chainring to indicate orientation (e.g. on Shimano original, there are markings that aligns with the crank arm). I tried to position it similar to the old chainring wrt. the helping pin. But since this is related to the ramps/pins, I guess this should not affect shifting to the large chainring?
Any other ideas? I find this really strange - it seemd to fit so nicely, and the shifting from inner to middle is "flawless". Chain is new.