steinrr

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.

CliffordK

I had issues several years ago with an Alivio derailleur that the shape of the inner plate on the front derailleur would tend to trap the chain when upshifting.

It is possible the chain was worn allowing it to twist some too, so a new chain might help.

My solution at the time was to raise the front derailleur 1/4" or so. Enough that the derailleur wasn't shifting with the overhanging part of the inner side of the derailleur.

steinrr

Thanks - will check how the chain position is related to this "track" in the cage.

(The chain is completely new - I've added that now as info in my initial post).

BCDrums

I have three TA chainrings on my old Shimano crank. I would ask if it is mounted the correct way, with the TA logo and lettering facing away from the frame, and/or the recesses/countersinks for the crank bolts facing toward the frame.

I have never seen an Alize ring in person, but the above is how you mount a Zephyr (110bcd) ring.

Good luck.

Leisesturm

If the shift TO the middle ring is going well then it has probably been mounted correctly. If the problem shift is TO the big ring, then the middle ring is not responsible for making that happen. The height of the derailleur should not be changed because the big ring has not been changed. Were there any spacers used between the middle and big ring? There should be some and they are usually sized to provide the correct spacing between the rings.
Edit: just took a look at the linked replacement ring. The o.p. mentioned orienting it with the helping pins facing inward. I see no pins or ramps whatsoever on the ring shown on the website.
Edit2: "the chain is (also) completely new ..." Hmmm. How was the new chain sized? A too short chain would give the problems being experienced.

dsaul

After looking at the original chainrings in this listing https://www.ebay.com/itm/12471785848...wAAOSwWCtgmPvC It is clear that the original has an offset mounting hole location. The replacement that you purchased is flat and that makes the spacing between the rings incorrect. You may need to use some chainring spacers to get the spacing correct.