Cable pull ratio on left hand downtube shift levers

[reohn2]

Brucey
I have that exact same mech on one of my Vayas running with Kelly's and it's in the same position when in the inner ring against the limit stop.There's no problems or excessive strain on lever or cable when changing up,its the same on two other bikes so I think you're mistaken.

[Brucey]

the front mech could be 1mm further over (which you wouldn't easily see BTW) and the cable tension force required could change by several kg. That is why this fault is so insidious; you literally don't see it coming. Things that make this more likely include

- short chainstays
- high front mech
- narrow chainline

I can't say for sure but the OP looks to have two out of three perhaps.

In fairness there is an easy test; if the middle to big shift is also hard work, there is probably something else going on, and it isn't just that.

For example I also note that the frameset is a vintage one that originally had different cable routing for the rear mech. It might be that the (original or revised) cable routing for the front mech is sub-optimal, and is simply binding badly or something.

One thing is certain; if an arm extension is made, the load required to move the front mech will be reduced; it is simply a question of whether that will be enough or if there is another problem as well.

cheers

[reohn2]

I'll reserve judgement until the OP has checked out the cable routing/lubrication,etc,whilst I agree an extension arm would provide better leverage all things being equal and as they should be,the cable strain and gear change should work well.

[Brucey]

a photo from the rear would help to identify if the cable really has much mechanical advantage over the mech or not. From the picture we do have it is impossible to be certain, of course, but that mech looks to me to me to be about as far over to the left as it can be. For example the pivots appear to have gone past the normal setting you might see; the upper pivots appear to be to the right of the lower pivots.

Most of these mechs get to be hard work (harder than normal) when they are that far over; IIRC the normal range of settings is such that the pivots might get to the point that one set is directly over the other on the small chainring, but not past that.

cheers

[reohn2]

Brucey
Look where the cable is in relation to the lower pivot.
Mine looks to be exactly the same on the same Tiagra front mech on a Stronglight Impact triple chainset with 24/34/46 rings on a 115mm UN54 BB in a 68mm shell.
With the mech on the inner ring limit stop and the gear wire taught the distance between lower pivot centre and gear wire is 5mm approx.
My other Vaya has a Sora triple front mech same rings same BB length but the distance between lower pivot and taught wire,mech against the limit stop in the inner ring position is 4.5mm approx.
Both bikes have 45mm chainline measured from centre of d/tube to middle ring centre.

Both operate perfectly,and I've no reason to think the OP's or any other similar set up regardless of type of gear lever would be any different which leads me to conclude it's a cable or lever related problem,or if it's a mech problem it's because it's stiff in operation due to corrosion in the spring or pivots or mech is damaged in some way,and not because the mech is too far over to the left causing a pivot disadvantage problem.

[peterh11]

Thanks all. Lots of ideas! I'm going to disassemble and rebuild this weekend with new cable (inner and outer) and without the Shift Mate, also testing whether the existing cable has resistance when disconnected from the derailleur, whether the derailleur is stiff and whether the lever is stiff when disconnected (ie test each part of the system separately). I'll check and clean out the connecting elbow for the Take-Off and the pivots on the derailleur as well

I'll check the leverage/position question too and post another photo if I suspect that is the problem, for others to give their assessment. I haven't noticed it being harder work going from inner to middle than from middle to outer, FWIW. When the Shift Mate is in the right position all is great, but it doesn't stay that way for long, and I don't think a clamp or grub screw will work, having studied it a bit. So I am focussed on trying to get all working without it.

Peter H

[peterh11]

Looking promising. Thank you all for your interest and helpful comments.

I checked each part of the system. No obvious problems except the lever being rather stiff, so I followed Reohn2's suggestion to put some oil into it, which has made a difference, thanks. I also sprayed the joints in the derailleur with WD40 as it seemed quite dirty, and that made it move more freely too (not sure if I should put some PTFE lube into it or just leave it - opinions on the Net vary - if someone has some experience with trying different options would be nice to hear about that).

Dismantled and rebuilt without the Shift Mate: used new Fibrax lined outer and PTFE coated inner, squirted GT85 into the curved noodle joint on the Take-Off and let it dry. Still seemed hard work though all running very smoothly.

However, ref Gregoryoftours' comment about wrapping the cable round the tab on the on the mount clamp: this model of derailleur doesn't have a tab, just a channel on the inboard side of the mounting bolt where the cable runs. However, this and Brucey's suggestion about making an extension arm got me thinking ... I found an old mech in the shed which does have a tab, swapped that on and ran the cable over it which not surprisingly makes a significant difference, because the contact point between the mount and the cable is now maybe 25% further from where the mount arm pivots as well as being further inboard. See photo (in this picture the chain is on the middle ring BTW). I also set the lever further round as another poster suggested, so that I have better leverage on that.

I'll try this out and if I want still more leverage I will try and make or find a clamp with a bigger/thicker tab or perhaps attach a block to the cable to push it still further from the pivot joint.

Peter H

[Brucey]

that does sound all rather encouraging. Some thoughts

- if the liner in the noodle near the gear lever is bad, that might cause additional friction. Usually you can pull the liner out of the noodle and then refit it turned 180 degrees , so that an unworn part of the liner is on the inside of the bend.

- re the front mech; if you just spray it with GT85 every now and then (especially whenever it gets wet), it ought to stay good for years and years.

- a longer extension arm will make life even easier. It isn't difficult to make something if you need to. Also, Campag used to make a little adaptor that converted the shift ratio of some of their front mechs; IIRC some folk have used this on shimano mechs.

cheers

[reohn2]

Brucey
There's no nylon sleeves in Kelly noodles they're just a short bent pipe,the they work very well if kept lubes.

peterh11
I've had Teflon coated cables gum up with the Teflon coming away from the cable,I much prefer stainless steel inner cables they're much slicker.
I'd also recommend using a Teflon grease such as Weldtite red grease for lubing cables,good stuff and stays put.I tend to get a bit on my finger and thumb and pull the cable through it,and fill the Kelly noodles up with it
GT85 is a bit thin for that job IMO.
I do lube mech pivots and springs with GT85 though as it cleans out the crud when you spray them.
If you get the lever in the right position with everything as slick as a slick thing gearchanges should be as easy and fast as STI's from any position on the handlebars

[Brucey]

for some reason I thought they were like standard V noodles, i.e. with a liner; I wonder if there is room inside them for a liner anyway? In some cases I have added a liner to fittings that never had one to start with.

cheers

[reohn2]

for some reason I thought they were like standard V noodles, i.e. with a liner; I wonder if there is room inside them for a liner anyway? In some cases I have added a liner to fittings that never had one to start with.

cheers

I don't think there is room but a standard V noodle could be substituted though the end that goes into the V arm needs reducing in diameter slightly.

[peterh11]

Brucey
There's no nylon sleeves in Kelly noodles they're just a short bent pipe,the they work very well if kept lubes.

peterh11
I've had Teflon coated cables gum up with the Teflon coming away from the cable,I much prefer stainless steel inner cables they're much slicker.
I'd also recommend using a Teflon grease such as Weldtite red grease for lubing cables,good stuff and stays put.I tend to get a bit on my finger and thumb and pull the cable through it,and fill the Kelly noodles up with it
GT85 is a bit thin for that job IMO.
I do lube mech pivots and springs with GT85 though as it cleans out the crud when you spray them.
If you get the lever in the right position with everything as slick as a slick thing gearchanges should be as easy and fast as STI's from any position on the handlebars

Thanks will keep this in mind. Thought I would experiment with the teflon coated cable - if it starts to play up I will go back to tried and trusted stainless steel and teflon grease. I think the big things here were the lever and the cable pull ratio on the mech. I have a couple of designs in mind for an extension to increase the cable pull still further if needed.

Taking the bike out for a couple of hours tomorrow morning so we'll how that goes!

Peter H