cavasta

Looking to upgrade my Dawes Galaxy tourer from bar end shifters to STIs.
Using Tiagra shifters and a Tiagra FD 4503 front mech, will this set up work:
48-38-26 chainset with 9 spd 11-32 cassette (my preferred choice).
Or will I be better of with this set up:
48-38-28 chainset with 11-34 cassette.
My main concern rests with the compatability of the front mech with the 26 or 28 tooth inner chain wheel. Shimano says the Tiagra front mech has a maximum capacity of 20 teeth. However, I've been told that it will accommodate a 48-38-26 chainset, which has 22 teeth max. capacity.

cycle_maven

I'm not that sure that the spec for the front mech is right, or if it is then it's the spec for the double variety rather than the triple variety- the typical road triple is 52-42-30, which is 22 teeth, and I've run 52-42-26 on my 105 and Ultegra front triple mechs with no issues (using brifters).

fietsbob

Tiagra is just a bit lower price tier than 105, and 'road' now is 52,53...
Road triple has a wider back plate to push the chain from the 30t, upward.

give it a try, avoid little-little combo .. learn your gear ratio pattern ..

'Trekking' is now applied to mid size, 48t .. Mountain .. 44t.

cavasta

The specs for the chainsets are correct. On touring bikes, the spec is always going to be very different to that found on a standard road bike. 52-42-30 would be wholly unsuitable for touring on, where the bike's main job is to transport loads (camping equipment, etc) efficiently and comfortably. Grinding away up a long mountain ascent on a fully loaded bike fitted with an inner chain wheel of 30 teeth would a miserable experience, regardless of whether a 32 or 34 was on the back. Using a 26 or 28 tooth ring, coupled with a 32 or 34 tooth on the back, on the other hand, makes such ascents both achievable and rewarding. My main concern, however, is one of compatability between the Tiagra FD and a 26 tooth inner chain wheel.

Chop61

It will actually accomodate a 48-36-24. I just set up a tourer with the 4503FD and it worked flawlessly, after I figured out the correct BB. Also with an 11-34. I used a Sram 9 speed chain...but did not have to remove any links.

cyccommute 

It will accommodate a 48/36/22 or, in my case, a 46/34/20. As a derailer for a triple crank, it's actually superior to it's more expensive cousins. Easier to set up and more forgiving for more gear combinations.

Chop61

Yes, it's one of those nice Shimano surprises, cheap, durable and easy to set up.

MichaelW

I use a Tiagra 4503FD with Tiagra STI shifters on a Shimano LX chainset (24/36/44 or thereabouts). It all works.

cavasta

Sweet! If it works with a 24 inner and 48 outer, then it must surely work with a 26 inner and 48 outer. Your set up both contradicts and disproves Shimano's claim that the 4503 has a 20 tooth max capacity. I wonder if they're just been over-cautious when they say that?