Changing up - Its happening Again

[CharlesF]

I have a Claud Butler with a 7 speed cassette and Shimano Acera rear derailleur, and I have had this problem before so have followed the expert advice but this time its still not working; to recap....

I have a problem changing up (from a lower to high gear), if I am in bottom (biggest gear) and want to change up 1 to 2, nothing happens. If I change again 2 to 3 the derailleur will then change to gear 2 while the control shows 3.

This happens all the way up so that when the control says 7 the gears are in 6, after a couple of rotations the chain will move to 7. However changing down 7 to 6 to 5 etc works perfectly.

Things I have done:
Cleaned and re-oiled the chain
Cleaned and lightly oiled the derailleur
Cleaned the cassette
Replaced the inner and outer cables.

 

[RedBike]

Either the gear cable isn't moving freely or there's not enough tension.

Change gear and then twag the cable near the shifter and near the rear mech. Is it tight like a guitar string in both locations?

 

[fossyant]

New gear cables - both the inners and outers. If they are a few years old, they will need changing.

 

[betty swollocks]

appears to be a simple question of getting the cable tension right.
First, put your shifter in gear 2 and the chain on the corresponding sprocket at the back.
Next, change the shifter to gear 3 and rotate the pedals, observing what the chain is trying to do. If it skips up too far, your cable tension is too tight and if it doesn't move or stutters up, it's too loose.
To increase cable tension, wind out the barrel adjuster (anti-clockwise) and to loosen screw it in. Continue to make adjustments this way until the chain happily moves up and down. Move the barrel adjuster in small increments, say a half a turn, each time.
video here

 

[Gary D]

Changing gear in the direction you describe is done by releasing the tension in the cable and then the spring pressure in the rear mech moves the pantograph over to the next smallest cog (or bigger gear ).
If the cable is sticking, then the spring pressure will not be great enough to move the mech - hence no shifting or even a "delayed" shifting.

As Fossyant says, it might mean new cables. However, first of all, remove the inner cable from the outer and clean it all down. Wipe the inner cable with a very light smear of thin oil when you assemble it again. A particularly problematic area is the short loop of outer cable just before the rear mech. I had exactly the same problem, ironically on my CB Hybrid, and water had got in to the outer cable and it had started to rust and jam the inner cable. A good clean sorted it though .

Hope this helps,
Gary.

 

[CharlesF]

Hi Guys

Thanks for all the help. It definitely wasn't the cables as I had replaced them. I think it is or was, the cable tension - I will know after a test ride. I was being too aggressive in adjusting the tension, instead of turning the barrel adjustor a quarter turn, I had been winding it in or out a number of turns.

I re-started riding three years ago and this is my first problem with the bike; I might sound like an old fogey, but 35 years ago my bike was a much simpler machine so I have some catching up to do.

Again, thanks for all the help.