Indexing problem - front gears

[lulubel]

I've been battling with this problem for a while, but haven't managed to fix it, so I hope someone else has some ideas.

I have a triple chainset on my new bike, Tiagra 9-sp triple shifters, Sora 50/39/30 crankset and Sora triple front mech. Ever since I fitted it, I've had the same problem. I can either have all the low gears OR all the high gears, but not both.

If I set the cable tension so that I can use all the gears on the big ring, the chain won't drop onto the granny ring. If I set it so that the chain will drop onto the granny ring, the chain rubs on the cage when on the big ring and using the 4 outer sprockets. This is with both limit screws right out, so they're not affecting it. I've also tweaked the height and angle of the cage, and what I've got now is the best I'm going to get there.

I've got a mega range cassette on it, so I've been using it like a standard double while I try to figure this out, but I've finally had to admit defeat and ask for help.

It seems to me that the indexed shifters aren't pulling the cable through far enough to access the full range of gears, but the only thing I've found that may be relevant to this is on Sheldon's site:

Some newer front derailers are designed with a choice of two cable attachment options. If the cable is run on the outside of the anchor bolt, away from the parallelogram pivots, the cage moves less far for a given cable movement, providing a lighter action, and easier fine trimming.

If the cable is run on the inside of the anchor bolt, toward the parallelogram pivots, the cage moves farther for a given cable movement. This is often necessary to provide correct functioning with indexed shifters.

I can't see that there's a choice of cable attachment options, but I think I could put the cable through on the other side of the bolt. This would put it closer to the pivot, so I think it would make the cage move further for the same amount of cable pull. From what I can see, this would be a "bodge", though (and none of our other triples are set up this way), and I'd rather get it working properly without having to set it up in a way it isn't meant to be set up!

Any suggestions?

 

[Crackle]

Sounds like you've covered the basics of which the Shimano technical documents are very good at telling you how to set up dérailleurs.

Height of the front cage over the large sprocket is critical, worth saying that even though you mention it's something you checked. Another thing to check is that the cable is properly engaged in the shifter slot, if it's not, it won't work properly, I know because I've done this. Is the cable running properly in the BB guides?

Is it not working when you're riding or is this static testing, there shouldn't be a difference but I've often found there is.

You mention a large rear cassette, is the rear dérailleur capable of this range and is the chain length correct for all of this. This should not directly affect the front dérailleur but can have a cumulative affect.

Beyond there not being anything obvious wrong, triples can be a right ar$e to set up and if at first it doesn't work, abandon the guidelines and experiment with dérailleur height and angle.

 

[lulubel]

Height of the front cage over the large sprocket is critical, worth saying that even though you mention it's something you checked. Another thing to check is that the cable is properly engaged in the shifter slot, if it's not, it won't work properly, I know because I've done this. Is the cable running properly in the BB guides?

I'll play around with the height again. I think I've covered everything, but you never know. I haven't checked either of the other things, so that's something else for me to look at.

Is it not working when you're riding or is this static testing, there shouldn't be a difference but I've often found there is.

Both. I did my indexing on the trainer (which is convenient) and it didn't improve or get worse out on the road.

You mention a large rear cassette, is the rear dérailleur capable of this range and is the chain length correct for all of this. This should not directly affect the front dérailleur but can have a cumulative affect.

Yes, I've got all the right bits. Long cage and 11-34 cassette, and that shifts like a dream. I kind of wish I'd done away with the road components and just used Deore XT throughout. It would only have cost me 2 teeth off the outer chainring, and the bike would be geared for loaded touring as well as general road use. You live and learn!

Beyond there not being anything obvious wrong, triples can be a right ar$e to set up and if at first it doesn't work, abandon the guidelines and experiment with dérailleur height and angle.

Yes, I'm learning that. I did the rear first, it took 5 minutes, and I was really pleased with myself. Then I started on the front.

My OH has just snapped a cable today, and I'm so glad it's the rear, or I think I'd be sending her to the lbs to get it replaced!

 

[gwhite]

The triple road set-ups can be a pig to get right but the Park method usually works fine. The tension of the front cable is critical and that is set with the chain on the middle ring and just missing the inside surface of the front cage when on the largest rear sprocket. Better to start from the beginning and work through. Properly set up , you should be able to get all of your gears.

 

[lulubel]

The tension of the front cable is critical and that is set with the chain on the middle ring and just missing the inside surface of the front cage when on the largest rear sprocket.

Weird. I've fiddled with it again this afternoon, and I currently have it set so the chain just rubs the inside surface of the cage in that ring/sprocket combination (I've sacrificed my 39x34 gear), and it now just misses the outside surface of the cage on all but the outer 2 sprockets on the big ring. It works fine on the granny ring. If I adjust the tension as you (and Park) say, I'll lose at least one sprocket on the big ring again.

I'm beginning to wonder if there are compatability issues between my 5 year old Tiagra shifters and my new Sora mech.

 

[RecordAceFromNew]

I can't see that there's a choice of cable attachment options, but I think I could put the cable through on the other side of the bolt. This would put it closer to the pivot, so I think it would make the cage move further for the same amount of cable pull. From what I can see, this would be a "bodge", though (and none of our other triples are set up this way), and I'd rather get it working properly without having to set it up in a way it isn't meant to be set up!

Any suggestions?

Am not too sure what you meant by putting the cable on the other side of the bolt, or why it would put it closer to which pivot, but since it appears the FD3403 sora mech has a ledge next to the bolt, if not already it is critical to get the cable over rather than under it before the bolt (pic. in 2. here), or else it would behave like insufficient cable has been pulled.

 

[lulubel]

Am not too sure what you meant by putting the cable on the other side of the bolt, or why it would put it closer to which pivot, but since it appears the FD3403 sora mech has a ledge next to the bolt, if not already it is critical to get the cable over rather than under it before the bolt (pic. in 2. here), or else it would behave like insufficient cable has been pulled.

Well, the bolt has 2 sides to it. One side is closer to the frame. The other side is closer to the pivot. It's quite obvious that you're supposed to put the cable on the frame side because there's a little groove for it to sit in, and I already had it on the correct side of the ledge because I thought it would be a bit weird to thread it all the way round it when every other cable on the bike (including brakes) is secured by just trapping it between a bolt/washer combination and a metal plate.

But the paragraphs I quoted from Sheldon's article make it clear that some mechs are designed so that the cable could alternatively run on the other side of the bolt, away from the frame and closer to the pivot point on the mech. Running it on that side of the bolt would mean the cage (which is on the side of the pivot opposite the bolt) would move further for the same amount of cable travel. It makes sense to me.

Out of frustation, I did try it earlier, and it did make the cage travel further. A lot further. One click of the shifters moved the cage from the granny ring to the big ring. So, I figured I was right in the first place, and my mech isn't designed to work like that, and put the cable back where it's supposed to be.

It still isn't working properly, though.

 

[lulubel]

(pic. in 2. here)

Having examined the instructions you linked for me more carefully - no, I didn't look at the instructions before fitting the mech because it seemed pretty self-explanatory - has anyone tried operating a front mech without removing the Pro-Set alignment block before?

It was rather noisy when I first got the cable connected, and I did think something flew across the room (but could never find anything, so I thought I'd imagined it). There's certainly no sign of anything there now that probably should have been removed.

Does this mean I get to be an honorary man?

 

[PpPete]

With some triples you can expect to "lose" two sprockets on each chain ring...but only because of chain rub on the FD cage makes those combinations too noisy, can't say I've ever come across not being able to achieve all 3 rings.
I'm guessing this cable attachment thing is sort of like a FD analogue of the "hubbub" mod on the rear derailleur cable routing (which changes the cable pull slightly to accomodate the slightly differences between Campag & Shimano).. Still a bit of a bodge though.

 

[MacB]

I've not set up a Sora triple FD but have set up a double and a Tiagra Triple, to be honest I didn't follow the instructions either and removed the block things without thinking about it. Didn't seem to matter though I still found it relatively straightforward. My method if it helps:-

1 - set the height in relation to the big ring, I found I could do this just by pulling the mech out by hand and a bit of trial and error

2 - tighten enough to hold height but still allow rotational movement for alignment purposes

3 - use the lower limit screw to avoid rubbing in big/big

4 - attach cable pulling it tight by hand, front shifter should be fully released at this point

5 - shift through rings and sort the upper limit screw

6 - fine tune alignment and limits to eliminate as much rub as possible then fully tighten FD clamp - can be some trial and error here as if you've left it too loose then the action of tightening can throw alignment slightly.

Oh and worth double checking chainline against the spec for the FD you're using just in case. An FD is a really simple item and what can be adjusted is very limited. My first install effort took ages and many errors but the last one took just a few minutes.

 

[RecordAceFromNew]

Yes, I've got all the right bits. Long cage and 11-34 cassette, and that shifts like a dream. I kind of wish I'd done away with the road components and just used Deore XT throughout. It would only have cost me 2 teeth off the outer chainring, and the bike would be geared for loaded touring as well as general road use. You live and learn!

Mmmm assuming you have a drop bar bike I am not sure full XTs would have worked the way you thought it would. Not only would an XT chainset have slightly wrong chainline for your sora mech, if you get an XT mech then your Tiagra shifter would definitely pull the wrong amount of cable for it.

Does the shifter happen to pull roughly 13.5mm of cable all the way across? and is the chainline 45mm?

 

[Scilly Suffolk]

I'm probably way off the mark, not being familiar with either triples or STi, but some of what you have written reminds me of what you would expect if the bottom, bracket was too long for the crankset.

 

[lulubel]

Mmmm assuming you have a drop bar bike I am not sure full XTs would have worked the way you thought it would. Not only would an XT chainset have slightly wrong chainline for your sora mech, if you get an XT mech then your Tiagra shifter would definitely pull the wrong amount of cable for it.

The reason I figured that would work better is because my XT rear mech is working perfectly with my Tiagra shifters. It was as simple as connecting the cable, and turning the barrel adjusted a quarter turn to adjust the tension. I've never had a rear mech/cassette combination run without even the tiniest rattle, but this is a delight to use.

Does the shifter happen to pull roughly 13.5mm of cable all the way across? and is the chainline 45mm?

I've got no idea. I don't know how to measure the chainline, but I can look it up.

After what I discovered last night, I think I figured out the problem, anyway. I suspect part of the Pro-Set alignment block is broken off and still jammed in the mech, which is preventing it moving through its full range of travel. I'll take it off and have a good look and see if I can find anything. If I can't, I'll just use the mech off my old bike for now. That's in perfectly good working order. The only reason I decided not to use it was because I was buying a new crankset anyway, and a new front mech was so cheap.

I'm probably way off the mark, not being familiar with either triples or STi, but some of what you have written reminds me of what you would expect if the bottom, bracket was too long for the crankset.

It's an integrated BB with cups, so it can't be the wrong. I did wonder if I should have had a spacer to put on the drive side, but that would have only pushed the chainrings over further and made it easier to drop the chain onto the granny ring. It wouldn't have solved the problem of bad chain rub on the big ring - in fact, it would have made it worse - so I figured that couldn't be the problem.

With some triples you can expect to "lose" two sprockets on each chain ring...but only because of chain rub on the FD cage makes those combinations too noisy, can't say I've ever come across not being able to achieve all 3 rings

That's why I'm beginning to suspect there's something still in there restricting its movement.

I've not set up a Sora triple FD but have set up a double and a Tiagra Triple, to be honest I didn't follow the instructions either and removed the block things without thinking about it.

I definitely didn't remove the block. My first thought when I connected up the cable and moved the mech with the shifters was that it seemed to take a lot of effort, and it moved over with a bit of a clang. I moved it up and down a couple more times - didn't have the chain on at that point - and it made a louder clang and a ping, and I thought I saw something fly across the room out of the corner of my eye, but couldn't find anything when I looked, and after that it changed up and down a lot more smoothly.

I think the thing that flew across the room was probably the broken off piece of the block (which snapped when it couldn't take the stresses it was under any longer) and the reason the travel on the mech is so limited is that there's still a bit stuck in there. It won't even move far enough when I move it with my hand, so it isn't to do with the cable.

Hopefully, I haven't broken it, but if I have, it's only about £12 for another one. It isn't as bad as my first attempt at building a computer, when I screwed the motherboard straight to the case without any spacers, and fried a £70 motherboard when I turned it on!

 

[Alun]

I have a triple chainset on my new bike, Tiagra 9-sp triple shifters, Sora 50/39/30 crankset and Sora triple front mech. Ever since I fitted it, I've had the same problem. I can either have all the low gears OR all the high gears, but not both.

Have you built this bike up from scratch? Or what set up was it previously?
I have recently fitted a Tiagra triple chainset in place of a compact set up and it came with a black plastic spacer which sits on the axle on the drive side, this is to give the correct chainline for the triple and to ensure that the granny ring doesn't catch the frame. Is your Sora chainset the same? Did you fit the spacer?

 

[MacB]

Lulubel, sorry assumptions made and terminology gets chucked about:-

chainline - this is the centre of the chainset measured from the centre of the bike, so how far out it is. Easy to measure with a rule and your FD instructions will give a recommended chainline, ie 45mm for a road one or 50mm for a MTB one. So a road FD sits closer to the frame, and doesn't travel as far out, as a MTB FD.

cable pull - for FDs road shifters pull less cable than MTB ones so the two aren't compatible, or very tricky to set up. Your combination should be fine.

Limit screws - these are to limit the range of FD movement and guards against overshifting so that you don't drop the chain either side. If you're not getting full FD range of movement required then, as well as checking for stuck bits, check that these screws aren't the issue.

Apart from that an FD only has two fitting aspects, height on seat tube and orientation/angle compared to imaginary bike centreline. If the chainline of your chainset is the same as the chainline indicated by your FD documentation, then it should work.