What do these bits do on my shifters ?

[cyberknight]

My shifters are shimano 2300`s.

They have a "noodle" where the shifter cables come out of the STI lever that twists ....

Does it actually alter the tension on the cables or is it just for protection?

Nothing shown on the tech docs , i have posted an image (not my bike ) and you can see them .

 

[Ravenbait]

Hard to tell from the pic but they look like barrel adjusters.

Sam

 

[Herzog]

I would also guess they are barrel adjusters for the front and rear mechs

 

[zacklaws]

Yes they are barrel adjusters, same as what I have on my Madone, it took me a while to get the knack of using them. If you tighten them, turn clockwise, you will see an insert move out from inside the housing, and doing this will tighten the cable.

I found the best way to tighten them on the move to make an adjustment was to have all the tension off the cable, the front mech you need to be on the smaller chain ring, the rear mech, the smallest sprocket and it becomes easier. I found that if their is a lot of tension on the cable, the whole adjuster turns and I think that it was because of this twisting the cable caused my rear cable to snap one day. Greasing them made it easier if there is tension in the cable, but it also made it easier for the adjuster to come loose, so on a long ride I usually have to make a few adjustments as I go along now, but its simple enough, just turn the adjuster till it starts to go tight and then you know all slack has been taken up.

If you need to use them on the move, just watch for that insert move in or out depending on what you are doing and then you will know your not just twisting the cable.