Can it be done?
(105 triple STI/Ultegra double chainset)
Would it be all out of whack or is it just a case of limiting the front mech?

I'd prefer responses based on real experiences rather than from folk who have just looked at the Shimano compatibility chart 😉

Will be fine. 9-speed STIs only came in triple compatible form (at least the Ultegra and 105 versions I have), hence I'm doing exactly that on a couple of my bikes.

10 speed will be ok too presumably?

Yes 10 speed will be fine.

Well I can't speak from experience (I've only got Campag in 10), but they've not changed the way the front mechs work, so it certainly should be.

cheers guys

I certainly put a 105 shifter on a 105 double and tripple (same lever) 🙂

Terra – did this very recently.

Things I learned:

1. For the inner ring, use the STI on its inner (ie. granny ring) setting. therefore big ring has the STI moving to "middle" ring position. You stop it overshifting in the usual way by screwing the high limit in on the mech.

2. I had real trouble with the front mech, mainly because of the increased depth of a triple mech, which meant it fouled the inner ring, however high I mounted it. I resorted to buying a new – double specific – front mech (Ultegra, natch, price matched at Evans in Manchester – £20). All worked perfectly then.

3. My vanity extended to fitting a short cage rear mech, though the medium cage that you need with a triple will work fine.

Ourmaninthenorth, I set mine up that way initially but couldn't stop making the third shift with the shifter. As the derailleur was on the high stop already, this resulted in a super tense gear cable and a VERY clunky shift down again.

I'd heard stories of shifters getting damaged this way so resorted to leaving the front mech in 'triple' mode and just using the low stop to stop the chain dropping off inside if I accidentally made the granny shift.

Seems to work…

if your going double, fit a specific double front shifter. the ultegra is a stupid fits all purpose double or triple shifter but the shifter internal ratchet is plastic. If you down shift to the smaller ring and accidentally try a further downshift the ratchet sheds its teeth and is useless. (i know from experience having broken mine in about 10mins riding up and down the street to check it was adjusted right). absolute rubbish..
ps the shifter ratchet is non servicable.

Yes, in exactly the same way you can use a triple mtb front shifter for a double chainring setup. I've always used the same technique as OMITN to prevent slack cable at any point. If you are trying to shift into a bigger ring when you are already in the big ring you truly are a monster.

Certainly with my 9-speed Ultegra you were supposed to set it up using the lowest two positions for a double – that way you get trim on both rings (no trim on big ring with a triple). Never had a problem setting it up so the cable stops prevented a further shift – you have to pull a fair amount of extra cable before it will ratchet!

Hmm, I found I almost couldn't help it, the shifter was so light that I would shift past the correct shift and into the third shift without even meaning to, so every time I went from small into big, i'd accidentally overshift and end up with a super tense cable and a very harsh downshift to correct.

Either way, I've got it to work now and also seem to get my trim on the big ring, so no worries!

Doesn't mean i won't be upgrading to the proper kit when the opportunity arises…