One word: don't do that! I could understand why someone who already has a road bike would want to adapt it for touring, but I can't understand why planning in advance to do such a conversion.
The typical road hike has:
- too short seatstays for stability and for installing panniers;
- probably no eyelets front and rear to install fenders (useful for commuting, amongst other conditions.
- sidepull brakes and narrow seatstays and forks; all of which limit tire size to 70025, probably. It's nice to tour on 700x37 (or at least 700x32) with fenders;
- some bikes are not stiff enough for a fast loaded ride;
- much too high gears and no triple, which means you'll have to change the crankset, the derailleur and the STI to convert to a triple and tour ($$$).
In fact, unless you think of racing, you should work the other way around.
Buy a real touring bike, which will probably come with the following gearing: 11-32 cassette and 52-42-30 chainrings. Negociate the following changes:
- Have the granny changed to a 26 (lower gears).
- Change the cassette for 12-28 or 13-28, so you'll get much closer range in the useful gears. If and when you do loaded touring, you might re-install the 11-32 cassette.
- If you do fast rides, change tires by 700x28 and pump them hard.
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