double chain-wheel with triple shifter

[pembo6]

Hi. I have re-posted this one. Was previously on the wrong forum. Hope that's OK.

I have a set-up with double front chain-wheel, but with a 3 speed/triple shifter. It seems to work fine if the inner/outer limit screws are adjusted accordingly.

My question is:

Is it best to have the shifting set so that the "missing" chain-wheel is the inner, or the outer chain-wheel? Eg, Set up as per normal, but then the third position shift throws the chain off the outside (adjust outer limit screw to stop this).
Or.......
Set up so the inside derailleur position is over the missing/ghost chain-wheel. Then adjust inner limit screw so derailleur cant throw chain on the inside.

It's easier for me to setup so the missing chain-wheel is the outer wheel. But risk throwing the chain off the outside if outer limit screw isn't set perfect. Is there a general standard on which way is best? And why?

Any advice would be greatly appreciated. Thanks

[JustJames]

Better to risk the chain falling off on the outside. If it falls on the inside it could damage the frame, or at least the paint, and may get jammed. If it falls off on the inside, just change gear back.

Letting the chain fall off on the inside is only preferable if you instal a chain catching device of some sort.

[twizzle]

The correct answer is to set it up using middle/outer. If you set up inner/middle there is a trim position just above middle that can get selected if you try too hard to shift, and once you get there, the cable tension jams the shifter and you have to undo the limit screw to allow the dump lever to work. A stack of people broke their shifters trying to force the dump lever. As long as you set the low limit properly, dumping too far just means you do an extra shift to get to the big ring.


Sent from my iThingy...

[bychosis]

Had mine set up and working well for ages.

Use chainring mid and big. Use shifter position low and mid. Can't undershift, cable doesn't go slack, can't over shift, limit screw prevents chain dropping off on the outside.

Edit: can over shift, but you have to try hard and pull the cable through the derailleur. From twizzle's method you would be able to put your shifter in low and not have the derailleur drop to low due to the limit screw leaving you with slack cable. I decided to use the method I did so there was no shifting position that was redundant.

[m@]

Had mine set up and working well for ages.

Use chainring mid and big. Use shifter position low and mid. Can't undershift, cable doesn't go slack, can't over shift, limit screw prevents chain dropping off on the outside.

Edit: can over shift, but you have to try hard and pull the cable through the derailleur. From twizzle's method you would be able to put your shifter in low and not have the derailleur drop to low due to the limit screw leaving you with slack cable. I decided to use the method I did so there was no shifting position that was redundant.

A quick google for 'broken shimano 105 shifter' might help change your mind

Though mine are still going strong after 4.5 years (but now setup using the mid-high positions as per Twizzle's post).

[bosvit]

The correct answer is to set it up using middle/outer. If you set up inner/middle there is a trim position just above middle that can get selected if you try too hard to shift, and once you get there, the cable tension jams the shifter and you have to undo the limit screw to allow the dump lever to work. A stack of people broke their shifters trying to force the dump lever. As long as you set the low limit properly, dumping too far just means you do an extra shift to get to the big ring.


Sent from my iThingy...

+1

As soon as I saw the headline I was hoping someone had mentioned the strain you put on shifters if you need to push hard against the outer limit screw to select the gear. Slack cable is not going to hurt anything if you accidentally shift down too far if you have it set up for Large, medium and small redundant