Chain shifts past the middle ring?

[summerdays]

More problems for me now... and I've tried looking it up in the book and thinking (that's a hard bit for me).

When cycling and wanting to change down from the largest ring to the middle ring, sometimes but not everytime, my chain is now jumping from the largest ring into the the smallest and then my feet go round like mad. I suddenly almost grid to a halt. I did pass my LBS yesterday but for some reason the shutters were down.


As I understand it ... tension moves it to the biggest ring and the spring moves it to the smallest one. Is that right?

What determines that middle ring position? Less tension?

(There are probably times when it doesn't change up, but I probably blame that on not pushing the trigger hard enough. And it doesn't feel as unsafe as the other way).

 

[jayce]

might have an inconsistant shifter

 

[02GF74]

you have 3 rings on the front? so will have a 3 speed shifter.

pulling the cable will move the chain onto successive bigger rings, the springs does the opposite, as you have ascertained.

the gear shifter has 2 small screws - these set the limits of gear shifter travel i.e. this prevent the chain from going past both the largest and smallest rings.

which brings us to what holds the chain on the middle ring - your question.

inside the shifter is a rathet that when engaged, pulls the cable so the gear shifter is in a position to hold the chain on the middle ring, there is a adjuster on the shifter that allows find tuning. It sounds like in your case, the chain going past the middle onto the small ring, that you require more tension in the cable - you achieve this by unscrewing the adjuster.

you find the adjsuer - a small knob - where the cable leaves the shifter.

check your gear cable at the gear shifter - they tend to break strands where they are held by the bolt to the gear shifter - fewer strands = weaker cable resulting in the symptoms you are seeing.

 

[gwhite]

The only time I've known this to happen is when the "H" screw is slightly too tight. This will just allow the shift from middle to large ring but places the cable under too much tension albeit still holding the chain on the large ring by the cog on the changer. However when the lever is moved to change from large ring to middle, the excess tension causes the FD to spring back too far and the chain is carried to the smallest ring rather than the middle. So, try unscrewing the "H" screw aquarter of a turn and see what happens.