Front Derailleur Issues

[pfm401]

Hello

I've been upgrading Shimano Revoshift to Tourney Thumbshift (SL-TX50) on my son's bike (Python Rock). Rear derailleur was really easy and no problem (and much improved shifting!) but front one is causing me a headache …

The main issue I have is that the shifter "maxes out" half way round and is really tight. If you imagine the shifter moving from "twenty to" to "twenty past" (which it does when it's not connected) I'd expect the small / middle / large chainrings to be engaged at "twenty to", "o'clock" and "twenty past" respectively. However they engage at "twenty to", "ten to" and "o'clock", and the shifting is really stiff. This suggests to me that the derailleur is trying to move too much for the shifting provided. I have the H screw all the way out so surely it can't be to do with limits (or the shift from low to middle would happen at the right place on the shifter)??

The derailleur is a Shimano FD-TZ31, which the vendor of the shifters has advised is suitable, so I'm a bit stuck! I suppose he could be wrong and I could try replacing the derailleur but want to make sure nothing else is going on first (like me being stupid!)

Any advice much appreciated!

Thanks, Paul.

 

[fossyant]

Do you have new cables ? It's one of the main issues.

Front mech's are really simple, unless it's a bargain bucket version. I ended up binning a brand new front mech on my daughter's bike for a decent level SRAM one.

 

[raleighnut]

Have you got the cable too tight?

 

[pfm401]

Have you got the cable too tight?

I wondered that. If I deliberately put the cable in slack, all it does is move the point at which it starts moving the derailleur ..

Maybe I should have mentioned it's a type of friction shifter (not indexed)?

 

[Racing roadkill]

Try winding the L screw clockwise.

 

[Milkfloat]

Are you sure you have your cable routing correct?

 

[C R]

I wondered that. If I deliberately put the cable in slack, all it does is move the point at which it starts moving the derailleur ..

Maybe I should have mentioned it's a type of friction shifter (not indexed)?

I think I run that combination of shifter and derailleur at some point, and worked fine. What you need to do is put the shifter in the lowest position, and pull the cable through to the derailleur. Set the L adjustment screw so that the derailleur is in such a position that with the chain the smallest ring does not rub on the cage, and clamp the cable taught, then use the barrel adjuster to increase the tension so that the derailleur moves as soon as you start turning the shifter lever. I think the problem is that you are leaving the cable too slack, so the shifter travels some distance before doing anything.

Hope this helps.

Edited to clarify how to set cable tension.

 

[pfm401]

I took it to the bike shop and ...
- Front derailleur is stiff with age (I replaced shifters but not derailleur) - to be cleaned
- Low shifting movement due to being a kid's bike so chainrings closer to frame. He showed me a brand new Revoshifter and set up friction shifter which stopped at "2" when on largest chainring.

Thanks for the help, looks like a bit if elbow grease on the front mech and accepting the limitations of the setup. Doesn't sound like the derailleur is fundamentally wrong for the shifters which is what I'd thought

 

[C R]

I took it to the bike shop and ...
- Front derailleur is stiff with age (I replaced shifters but not derailleur) - to be cleaned
- Low shifting movement due to being a kid's bike so chainrings closer to frame. He showed me a brand new Revoshifter and set up friction shifter which stopped at "2" when on largest chainring.

Thanks for the help, looks like a bit if elbow grease on the front mech and accepting the limitations of the setup. Doesn't sound like the derailleur is fundamentally wrong for the shifters which is what I'd thought

It is strange that the derailleur doesn't have enough throw, were both limit screws fully out when the mechanic showed you where the shifter stopped?