Front derailleur problems

[RecordAceFromNew]

Rick we are all delighted to be able to help others, but I am afraid we are doing it remotely here so guesses have to be made, and potentially omissions and mistakes can be made by all of us.

IMHO going for a tiagra front mech is not itself the obvious answer. It is because it is a road mech, and you have mtb shifters. A mtb shifter does not deliver the same cable pull a road front mech expects for each "gear", and the difference is quite significant (your front shifter moves 44% more cable per "gear" a tiagra expects). Alas like many things in this business mixing in a road front mech might work just fine for some in some circumstances, but if I were you, I would look for a solution elsewhere first.

The problem you have, is that you have mtb shifters, a mtb front mech, but a road chainset.

Solution 1

The silver lining, is that road and mtb chainrings have the same pitch (i.e. distance between rings). So if we park the 12T/10T problem for the moment, essentially the problem you have is that your road chainset is approximately 5mm too close to the frame.

If I understand it correctly you said you are using a 110mm long / 68mm shell bb. If so by my estimation if you change it to a 118mm long one, your chainline should be practically if not exactly 50mm. Such a bb can be bought for peanuts or, more preferably, £15 including p&p.

However since there is this 12T/10T difference issue outstanding, if you are comfortable doing it, before swapping bb what I would suggest is to do a cost free experiment first: I would remove the drive side chainset, and wrap a layer or two of oven tin foil evenly and tidily on the tapered bit of the square taper, and reinstall the chainset as normal. The objective is to utilise the tin foil as a shim to move the chainset out by roughly 5mm. It shouldn't take many layers, but it has to be done by trial and error.

Once you have your approximately 50mm chainline, you can try setting the front mech up following this. Chance is you should be able to hit all the gears without undue rubbing, including being able to use the large front ring, by setting the front mech height by avoiding clash with the middle, not large ring.

Solution 2

A more costly but technically more correct alternative is to swap the road chainset for a mtb one, but be aware it also needs a matching bb, which is probably not the same as above. I have provided a link to a compatibility chart earlier. You are the only one who can decide whether this is preferable compared to Solution 1 (with or without swapping the middle chainring).

Solution 3

If you wish you can swap the front mech for a road one, but you may well have to swap shifter(s) too.




I hope whichever solution option you choose works well for you. If not please do come back.

 

[MacB]

Some of the confusion could be down to a reply I gave Rick by PM, which I'm now not so sure on. I thought the original setup on my flat bar hybrid, Giant CRS Alliance 2008, was Tiagra front and rear mechs, with Deore shifter pods, all 9 speed. I've just had a look at the archive specs and they show Tiagra rear, Shimano 440 9 speed FD and trigger pods, ie flat barred road, to work with the 30/42/52 road chainset. Problem is that I'm not sure exactly what it came with now as I've made so many changes, having just had a look the current configuration is:-

Original FD, just says Shimano 9 speed on it - but does look like images of the 440 FD's on the Shimano website
RD is now an XT shadow rapid rise
Shifters are Dura Ace bar end, indexed on right and friction on left.

Looking at my spares box I can't remember what the original shifters were but I have a set of dual control Deore 9 speeds(combined trigger pods and brake levers) in there which I have run on the bike, with this FD, and it worked fine. These were put on by my LBS and they dialled in the shifting for me, never mentioned any problem re FD.

But I hadn't considered the chainline issue and agree with RecordAce here, trying to match chainlines would make sense.

 

[ricksavery]

I seem to have been a complete dunce about the incomatibility of road and MTB mechs / shifters, as well as the chainline issue.
At the risk of sounding ungrateful for your advice RecodAce (which I'm not at all), I really want to keep the chainset I've got, so I can either change the bottom bracket or the front mech. I think the experiment you suggest to adjust the chainline is very elegant and learnt loads thinking about how this works, and, although it is the cheaper option (annoyingly recently bought a new BB) I would prefer to change the front mech. My reasons, i suppose, are not particularly logical, it's just that I would rather have a bike that I know has the 'right' components than one which has the 'wrong' components but have been made to work, however effectively and elegantly.
This probably seems odd, but building this bike has been a bit of a labour of love, and there is a certain aesthetic pleasure in standing back and looking at a bike that is 'right'. Does that make sense, or should I see a shrink ? (I suspect the answer is 'yes' and 'yes')
So I think I am back to changing the front mech for a road one. Chain Reaction have a LH only R440 shifter for £9 (which I have ordered) which is the flat-barred road shifter. Although it says it is specifically for the R443 front mech, as it is essentially a road shifter, is it reasonable to assume it would work with the Tiagra ?
Thanks MacB for clearing that up - again, because of my ignorance of the whole road/MTB difference, I didn't know enough to be confused :-) (actually that sounded really sarcastic - not meant to)
Hopefully you will think my choice a sensible one, and let me say again how much I appreciate the time and advice given.
I've learnt an awful lot more about my bike, and bikes in general during the course of this thread. Thankyou

 

[RecordAceFromNew]

A couple of comments:

1. Although Chain Reaction tells you that the left / front shifter you said you have bought is a R440, it is not. It is actually a R441 (or more accurately a SL-R441). IMHO you should not have bought it (reason to follow). The associated right hand / back shifter you didn't buy is the R440.

2. The above label distinction is important because otherwise you can't look up a compatibility chart and make sense from it. The chart on the second page here is the applicable one for your new shifter.

3. As you can see it can work with 3 front mechs, but since FD-R440 is for a double chainset and is no good to you, the remaining choice is FD-R443 or FD-R453. These are "tiagra level" shifters but are not tiagra per se (and without the tiagra label on it, and reason to follow).

4. Both the FD-R443 and FD-R453 assume 45mm chainline, which I understand is what your chainset delivers. Their principal difference is that the 443 is designed to accommodate a 52T large ring profile and minimum large/medium tooth difference of 10T, while the 453 is designed to have a 50T large ring profile and minimum large/medium tooth difference of 11T.

5. Since your chainset has a 48T large ring with 10T difference, you have to make a somewhat imperfect choice. Either option will cause your front mech tail to be further back from the chainset than optimal, with the 453 also perhaps a little bit higher to avoid clash. I am bringing this up only because from what you said it might affect your aesthetic enjoyment...

6.The good news is that chance is either of these front mechs will work just fine with your chainset.

7. The reason you can't use a "real" tiagra front mech (e.g. the FD-4503 on page 1 of the chart) with the R441, is because as a Shimano "flat bar" front shifter the R441 has the same cable pull as their mtb equipment (as opposed to the road "drop bar" equipment). This is also the reason why IMHO you shouldn't have bought it - either of these front mechs should work with your existing shifter. I should have proposed these mechs as another solution option earlier, but unfortunately they didn't cross my mind at the time.

9. Regarding the FD-4503, as I have said before in this business sometimes what the manufacturers say wouldn't work will work for someone in some circumstances. I am saying this because I wouldn't be too surprised if the SL-R441 or your mtb shifter can be made to work with the FD-4503's of this world by fiddling, but the bottom line is that it is not optimal, will be finicky, and will stress the system when on the large ring, so I would not recommend one goes there.

I do fully understand how one's hand itches for one's wallet uncontrollably when one looks at bike gears. Many of us have the same ailment; and it can get worse...

 

[ricksavery]

Bugger! I was really hoping you'ld come back and say 'good choice, that will work'

Seems as if every choice is a compromise. So the 443 / 453 with R441 works for flat bars, but with larger ringed chainsets, whilst the Tiagra mech would be best with my chainset, but only works at its best if I have drop handlebars - which I don't want.

I think my choice of flat bars on a tourer is not helping, but just can't get on with drop bars.

Incidentally, the left-hand shifter arrived from Chain Reaction, and it has R440 on it, would this be different ?

My aesthetic enjoyment is looking like a bit of a luxury. Ideal situation would be the Tiagra mech with some way to shift on flat bars. I seem to want something that doesn't exist :-)

 

[ricksavery]

Just re-reading some of the posts and ...

'Rick we are all delighted to be able to help others, but I am afraid we are doing it remotely here so guesses have to be made, and potentially omissions and mistakes can be made by all of us'

Please don't think that my comments were a complaint, and I hope I didn't cause any offence, merely a clumsy attempt at thanks

Also had a cunning idea ... as my frame has braze-ons for downtube gear levers, could I not fit just the left-hand side one for the front mech ? I assume this would be a friction-only shifter (no experience of these at all), and, in a sense,a correct shifter for the Tiagra ?

 

[RecordAceFromNew]

Rick in case there is any misunderstanding the 50T/52T are maximum outer ring limits - it doesn't mean those front mechs won't work well with your 48T chainset since the difference is so small. I was just pulling your leg regarding your aesthetic requirement.

In fact even the tiagra triple road mech RD4503 has 50T max 11T minimum difference limits, same as the R453, as can be seen from here and here.

I think a longer bb, or switching to a suitable mtb chainset/bb, or switching the front mech (to e.g. a R443/R453) would all work well, and would all look just fine!

ps

1. Sure a friction shifter should work.
2. The left hand shifter is a SL-R441 according to this and the compatibility charts etc.

 

[Crepello]

Wow - this is a long un! May I suggest that if you feel that the issue is largely to do with the mech having to fit higher up for the 38T ring, then you order a 36T ring from Spa and so obtain something more like the Deore trekking chainset. Here we go. £11 - worth a punt?

 

[ricksavery]

No problem. I knew you were pulling my leg - frankly it needed pulling. I'm getting far too picky about all this
Cheers