Bicycle Mechanics - another shifting problem question

I have a roadbike with a 7 cogset which shifts fairly well except when shifting DOWN from the 2nd to the 3rd (I'm assuming that the largest is the 1st). It seems to always get stuck in 2nd when trying to shift down and it only happens on this gear. I have tried many times to adjust the "adjusting barrel" clockwise to loosen the cable but that affects shifting upwards. Could this be a sign of a bad derailer or do I just need to keep on tweaking?

Try cleaning and lubricating your derailure

Indexed or friction shifting?

Typically, it is indexed if the shifter goes "click, click" when you shift, and it is friction otherwise (or if your bike is more than 15-20 years old).

If you have downtube shifters or barend shifters with a choice between indexed or friction, choose the "friction" setting and try to shift to see if it now works correctly.

When you are at home, lift the rear wheel. One way to diagnose the problem would be to set your shifter in "5", and pull your cable by hand, somewhere along the downtube. By pulling the cable by hand, you should be able to bring the chain to 1st, 2nd, 3rd, 4th and 5th gear, and the change should be gradual. You might need a bit of practice to get it right, but after 3 or 4 trials, you will get it easily.

It things shift smoothly by hand but not by the shifter, the problem is near or in the shifter. If things don't shift smoothly by hand, the problem should be further down.

Possible problems to watch :
- lubrication of derailleur and cables (especially if you go in mud, snow or sleet);
- a frayed cable.

A frayed derailleur cable may jam where a broken strand interferes with a cable ferrule, the shifter barrel, or the point at the bottom bracket where the cable turns. This would made unreliable upshifts (2 to 3, for example), because it's only the derailleur spring that moves the chain to the rightmost cogs.

Regards,

A point made by mgagnonlv might be worth checking first before adjusting anything. It was the cause of the same problem on my bike.
If your cables run under the bottom bracket shell in guides then the guides may well be rusty or gunged up causing friction on the cables.
If this is the case you will probably need to replace the cable inners if they are rusty.

:)

From your post, I assume the 1->2, 3->4, etc. upshifts are OK. Does the selection of chainring affect your 2->3 upshift? How is the clearance between your derailleur cage and your cogs? The other respondents make valid suggestions, as well. Please let us know what works for you.

Thanks for all the suggestions.

My shifter, located on the down tube, is indexed.

The problem is consistent with both chainrings.

As soon as I got home, I lubed the derailer. I know the derailer is clean because I had just painted the frame - while everything was off, I cleaned everything. Lubricating didn't fix the problem, but it eliminated some squeaks.

I tried pulling the cable by hand and the problem persisted, which led me to believe that the problem is in the derailer.

Anyway, I tried loosening the angle adjustment "B-tension" and that seemed to have done the trick.

Thanks for all your help! :

If the problem reappears, try the following:

- Either remove the chain or remove the wheel, so the derailleur is able to move freely left and right.

- Try to upshift and downshift, and see if there is any obstruction in the derailleur parallelogram. There might be some debris there.

Regards,