Tiagra 9 speed triple front derailleur smallest chainrings?

[deliquium]

Current set up (approx 10 year old) Tiagra 9 speed triple STi levers/brifters, triple band on front mech, 50/40/30 Tiagra chainset.

Has anyone successfully changed a to smaller ringed triple chainset? Is the Tiagra FD likely to work (keeping the Tiagra STi levers) for example on a Spa Cycles XD2 46/34/24, with corresponding length ST BB to retain the 42.5mm chainline?

Presumably if one tried to go MTB 44/32/22*, whatever BB could be used will increase the chainline to definitely muck things up?

Bike's a Condor Fratello

* I did try on another bike a while ago - a SPA CYCLES 104 Touring Triple Chainset 44/32/22 but it was impossible to get a chainline under 50mm as the spider would foul the BB shell with any shorter BBs

[reohn2]

On my Vaya I've used a Stronglight Impact c/set with a 9sp Triagra triple front mech with 46/34/24,48/34/26 and currently 39/24 rings with a bash guard in the outer ring position(thanks for the donation ) all with a UN54 115mm BB with friction lever and with road STI's.
I've also used a Shimano 44/32/22 s/taper MTB c/set(Alivio I think) on the same bike with the same mech and UN54 110mm BB.
Shifts are clean crisp and precise

[deliquium]

^ Ta very much John

I've just edited my post, as want to keep the Tiagra STi levers working with the Tiagra FD - only changing the chainset and BB

But if I read your post correctly, that shouldn't be a problem as you have done that already = good news

[iandriver]

I run a 9 speed Tiagra tripple still. I simply swapped out the inner 30t ring for a 26t. It all works fine, people have been doing this to Shimano tripples for years. Spa will sell you an inner ring cheaply.

I'd only consider a new chainset if you want to go right down to something like a 22t inner ring.

Edit: looks like you can go as low as 24, http://www.sheldonbrown.com/harris/chainrings/74.html, with a warning

[deliquium]

I run a 9 speed Tiagra tripple still. I simply swapped out the inner 30t ring for a 26t. It all works fine, people have been doing this to Shimano tripples for years. Spa will sell you an inner ring cheaply.

^ Thanks iandriver, however the lower middle and outer ring are very much required too - deffo max 46 and 34 and then might as well have a 24. Also the current Tiagra 40 ring is showing signs of wear after ten years.

Just wanted to know if the Tiagra road STi and FD will cope with 46/34/24

But good to know the Tiagra C/S will go down to a 26 inner

[Valbrona]

From limited experience, 26 is fine, but anything smaller and chance of problems.

[Tigerbiten]

You need 2mm per tooth.
So dropping from 50/40/30 to 46/34/24 while keeping the same chainline, you'll just need to move the mech down by 8mm without it catching on the chainstays as this is what tends to stop the downward movement of the mech.
Also you'll need an extra 4mm between the chain and the bottom of the cage for the extra drop in the chain due the tooth difference increase.
So a little measurement will tell you if it's at all possible.
Then how it's a question of how well it will work due to the smaller chainrings increasing the horizontal mech-chainring distance.

Luck .......

[deliquium]

On my Vaya I've used a Stronglight Impact c/set with a 9sp Triagra triple front mech with 46/34/24,48/34/26 and currently 39/24 rings with a bash guard in the outer ring position(thanks for the donation ) all with a UN54 115mm BB with friction lever and with road STI's.
I've also used a Shimano 44/32/22 s/taper MTB c/set(Alivio I think) on the same bike with the same mech and UN54 110mm BB.
Shifts are clean crisp and precise

So can I just clarify that you have successfully used a Stronglight Impact (same as? Spa Cycles/Sugino XD2) 46/34/24, with a 115mm UN BB, a 9 speed Tiagra triple FD and 9 Speed triple Tiagra STi levers?

If I'm thinking straight? Did that give a ~45mm chainline to the centre of the middle ring?

I've not got the bike in question here at the moment, so am unable to measure the current chainline with the Tiagra 50/40/30 and its hollow axled, outboard bearinged BB.

I should explain, this is not my bike, it's a local friend's, but I will probably be asked to do the work, as the owner doesn't want to ask any LBSs to get all 'tricky' with these sort of customisations. As they fear they will be told to . . . .

[deliquium]

Thanks Valbrona and Tigerbiten for both your posts too and info noted.

This kinda lark (which I've been doing/adddicted to almost all my cycling life is never without risks

[reohn2]

So can I just clarify that you have successfully used a Stronglight Impact (same as? Spa Cycles/Sugino XD2) 46/34/24, with a 115mm UN BB, a 9 speed Tiagra triple FD and 9 Speed triple Tiagra STi levers?

Yep.

If I'm thinking straight? Did that give a ~45mm chainline to the centre of the middle ring?

No,the chainline is 40mm with a 115mm UN54
I have the same chainset on my Genesis Vagabond which has a 45mm chainline with a 122.5mm UN54 BB
I've just measured them

[deliquium]

So can I just clarify that you have successfully used a Stronglight Impact (same as? Spa Cycles/Sugino XD2) 46/34/24, with a 115mm UN BB, a 9 speed Tiagra triple FD and 9 Speed triple Tiagra STi levers?

Yep.

If I'm thinking straight? Did that give a ~45mm chainline to the centre of the middle ring?

No,the chainline is 40mm with a 115mm UN54
I have the same chainset on my Genesis Vagabond which has a 45mm chainline with a 122.5mm UN54 BB
I've just measured them

You'se a superstar