Triple/ mech compatibility.

[bigjim]

Before I start dismantling things. Does anybody see a problem with a 24/34/46 triple chainset operated by Sora shifters and a Tiagra triple front mech?
Cheers. Jim.

[Brucey]

some potential issues (provided the sora shifter is a triple.... ) are that the tail of the FD may be close to the chainstay on some frames, and that the chainline might be too wide (if it is an MTB chainset) for the FD to work optimally.

cheers

[Tompsk]

I have a Tiagra 10 speed triple front changer (fd4603?) on a 9 speed 48, 38, 28 setup.

The things I found were that the curve of the cage is optimised for 50, 39, 30 teeth chainrings and the further away from these you may find the performance is compromised as you try to set how high up the seat tube the cage is - I think optimal height is so the middle chainring is in line with the slight recess in the back of the cage rather than the outer plate being 3mm above the large ring. This is a bit tricky to set.

Also the cage is probably designed for the width of a 10 speed chain. I'm running a wider 9 speed chain so may be having to trim the position (via a friction dura ace bar end lever) more often? I can't comment of suitability of Sora shifters, if the chainring spacing is the same that is a good start. With Sora shifters it may be better to get a Sora front changer as you can't trim the position of the changer with STI.

Over all my set up is not a problem for me but YMMV! I will probably try a 24 inner at some point, I hope this won't be a problem as I understand the middle and outer ring changes are more sensitive to size on a triple.

[NewHorizon]

My 9 speed triple set up with XT 22/32/44 chainset, XT rear derailleur and Tiagra front derailleur works very well with Tiagra STI's - the only thing we had to do was swap the bottom bracket spacers - one on the drive side, two on the opposite side (as Bruce suggests). The FD was set as close as possible to the outer ring. I can trim the FD in the middle ring with the STI.

[Tompsk]

I can trim the FD in the middle ring with the STI

Can this be done whilst on the move from the lever or by tensioning the cable whilst at the side of the road / workshop? If it can be done on the move from the lever I might reconsider STI for my set-up!

[NewHorizon]

On the move - there are effectively two middle positions - a short nudge on the lever will click it over from one to the other or vice versa, trimming the FD to stop chain rub. All that is needed and works very well.

[Brucey]

most road triple STIs have 'trim clicks' designed in. This pdf explains how they work for some (obsolete) models of shimano road STI.

https://web.archive.org/web/20100705001424/http://bike.shimano.com:80/publish/content/global_cycle/en/us/index/tech_support/tech_tips.download.-Par50lparsys-0030-downloadFile.html/06)%20Trim%20Function.pdf

Current ones are similar, but it seems that shimano have decided to no longer provide useful information like this to their customers....

cheers

[reohn2]

Jim
I have a Tiagra front mech on one of my Vayas,the frame has a 75mm BB drop and a 72.5degree seat tube angle,It has a Shimano Acera s/taper MTB chainset fitted with 44/32/22t rings and works fine but it's on friction change.
I've also run the same mech with a Stronglight Impact chainset with 46/34/24t rings on a couple of other bikes with STI changes and they worked fine too.
IMO the combo will work fine on yours