Front mech problem

[Dave Davenport]

So, I've been giving my old Kinesis Racelite T a bit of a rebuild after being given some 10 speed Shimano parts, didn't have a front mech but as I'm running bar end shifters which are friction on the front I thought the old 9 speed front mech would work ok (34/50 chainset).
Anyway, I've been tinkering with it for ages and just can't get it shifting properly, as soon as it's set just far enough over to shift onto the big ring it's pushing the chain over and off, I've tried moving it across the full range up & down with no improvement.
I've compared it to a 10 speed front mech on another bike and it's 3 or 4mm wider so I'm assuming that's why I'm having problems?

 

[si_c]

You need to adjust the derailleur limit screws if it's pushing the chain over the top of the chainset as the new chainset probably sits a little inboard compared to your old one.

 

[Dave Davenport]

You need to adjust the derailleur limit screws if it's pushing the chain over the top of the chainset as the new chainset probably sits a little inboard compared to your old one.

Done that.

 

[Ajax Bay]

The position of the H limit screw must allow enough movement to actually make the shift, otherwise: what's the point? But that change relies on the inner cage plate pushing the chain across. And if the cage really is 3mm wider then of course that allows the cage's outer plate to be far enough out to let the slightly narrower 10sp chain to escape outwards.
Surprised the cage width is that much different.
A temporary mitigation is to drop the height of the FD to an absolute minimum (cage only 1mm above the large chainring as opposed to the recommended 2-3mm.
And given you're using friction shifters, a steady, incremental movement of the lever when changing up, and then returning slightly, has merit.

 

[Dave Davenport]

Yep, I've tried moving the mech so it just clears the chains ring by a whisker. I was also surprised at the difference in width but I measured it with a near enough gauge (aka a Vernier) and it's definitely a good 3mm wider internally. I've set the limit at just enough to shift up which is ok when the chains in the top half of the block but it's dropping over the big ring when in the lower part. Think I'll just shell out the 20 quid for a 10 speed specific one, not spending much money on anything else at the moment anyway.

 

[Dave Davenport]

So before ordering a new mech I tried taping a 2mm shim on the inside of the outer plate, works fine! Have ordered a 105 one from Chain reaction for 17 quid.