Front derailleur not shifting to 3rd and back

[SigDas]

QUESTION: Does replacing chain and/or rear cassette impacts how bike shifts from 2nd to 3rd and back? What if I replace those and the bike still doesn't shift? Maybe I missed some important detail?

Info:
* Drivetrain is 3x8
* Front derailleur low and high limit screws are set up properly
* Cables and housing were replaced and lubricated slightly (moves smoothly)
* Shifting level works smoothly
* I cleaned the drivetrain very well with white spirit and acetone and waxed the chain with silca wax.
* Front derailleur is clean and slightly lubricated
* Bike used to shift properly with current front/back derailleurs and shifting levers so they are compatible
* Front derailleur height and angle are adjusted properly
* Bike had index shifters

Possible problem areas:
* Bike has new 8 speed e bike chain even though it is regular bike
* Bike has badly worn out rear cassette to the point that it skips the chain on some rings (owner of the bike currently can't afford new cassette but want's smooth gears)

PROBLEM: Problem is that the front derailleur doesn't shift smoothly (delay from 5-15 sec very bad) from 2nd to 3rd and back from 3rd to 2nd chainrings. It works perfectly from 1st to 2nd and back. Now I tried adjusting the cable tension, however if I tighten it, then the chain doesn't shift from 3rd to 2nd at all. On the other hand if I loosen cable then it only shifts from 3rd to 2nd and doesn't shift up to 3rd again.

 

[BikeGremlin]

QUESTION: Does replacing chain and/or rear cassette impacts how bike shifts from 2nd to 3rd and back? What if I replace those and the bike still doesn't shift? Maybe I missed some important detail?

Info:
* Drivetrain is 3x8
* Front derailleur low and high limit screws are set up properly
* Cables and housing were replaced and lubricated slightly (moves smoothly)
* Shifting level works smoothly
* I cleaned the drivetrain very well with white spirit and acetone and waxed the chain with silca wax.
* Front derailleur is clean and slightly lubricated
* Bike used to shift properly with current front/back derailleurs and shifting levers so they are compatible
* Front derailleur height and angle are adjusted properly
* Bike had index shifters

Possible problem areas:
* Bike has new 8 speed e bike chain even though it is regular bike
* Bike has badly worn out rear cassette to the point that it skips the chain on some rings (owner of the bike currently can't afford new cassette but want's smooth gears)

PROBLEM: Problem is that the front derailleur doesn't shift smoothly (delay from 5-15 sec very bad) from 2nd to 3rd and back from 3rd to 2nd chainrings. It works perfectly from 1st to 2nd and back. Now I tried adjusting the cable tension, however if I tighten it, then the chain doesn't shift from 3rd to 2nd at all. On the other hand if I loosen cable then it only shifts from 3rd to 2nd and doesn't shift up to 3rd again.

Hi,

That's an interesting problem.

A short answer​

Noting this just in case:
It is common with many shifters and derailleurs that you must keep the shift lever pushed while you are shifting to a larger front chainring, until the shift is done (not just get it to click and let go). That gives it just that little bit of extra needed push to make a quick shift. This can especially be the case if the housing can compress (high-quality shifter housing has longitudinally aligned steel wires to reduce compression - see brake vs shifter housing for details).

That aside (if it doesn't help):
I would try unscrewing the front derailleur's "High" limit screw by a full turn and see how it performs, for a start.

A longer answer with explanation​

I've made two videos to help with shifter and derailleur tuning:

• Bicycle derailleur tuning academy
  (I know, a pretentious sounding title )
• Problems preventing you from EVER tuning your derailleurs properly
  (if the first video doesn't help)

It is generally easier to figure out a problem if you can see and adjust the bicycle first hand, so those videos might be more helpful than my reply. Still, these are my thoughts on the problem:

• A new chain will flex less laterally compared to a worn chain. That makes it act more responsivelly to derailleur movement. For example, where a worn chain is reluctant to "hop" onto a larger sprocket/chainring, the new chain might shift more eagerly, for the same derailleur movement/setup.
• Likewise, a new chain may experience the (more or very little pronounced) chain suck effect on worn chainrings, and generally not mesh nicely with the worn teeth.
• Finally, a new chain might be just a 0.1 mm wider or narrower compared to the old chain (while still being within the standard chain width specs), and that could cause it to shift differently.

Those are the few things that could affect shifting. Apart from those, if nothing else was changed on the bike, the new chain should be fine, even though it's rated as an e-bike chain.

If everything is properly tuned and aligned, as I wrote at the start, I would try unscrewing the front derailleur's "High" limit screw by a full turn. Just to see if that helps the chain shift to the largest chainring (if it causes it to overshift and drop, I would try to fine-tune and double check, of course).

Another thing to consider (double check) is the point where the cable is attached to the front derailleur (if cables were changed). There is often an exact groove and angle at which the cable should enter before it is clambed by the pinch bolt. Sometimes with a small pin to keep the cable's entry line at just the correct radius from the derailleur's pivot. If a cable was not attached properly or slipped past the "protrusion thingy" (not sure what the correct English tech. term is), that could cause shifting and tuning problems.

Cassette change effect​

A new cassette can affect front shifting if it has different sized sprockets, for example. That can change how tight the chain is in different gear combinations, and its height and angle when it comes off the cassette's top section towards the front derailleur. The shorter the chainstays, and the more different the cassette sprocket size, the greater the effect. Still, the effect is generally very minor, if noticeable at all (unless the shifting was "just, barely working" before the cassette swap).

Hope this helps.