Originally Posted by
mjordan123
1. What are advantages / disadvantages of a triple vs double?
Given the same cassette, triples give you more gears at the low end. Or you can use a more tightly-spaced cassette with a triple and have the same range of gears as on a double, but with smaller changes between the gears. Doubles are perceived to be cooler, more racy, and simplify front shifting. Triples are more versatile and weigh less than 100 grams more.
Originally Posted by
mjordan123
2. What all is involved in making the change? A new double crankset and front derailleur? I am assuming I would not have to change anything on the rear 9-speed 105 cassette?
You'd need to change the crankset and the bottom bracket. Changing the front derailleur would be optional, your old one will probably work fine. Nothing needs to be changed at the rear (again, you could change the rear derailleur to one with a shorter cage, but there wouldn't really be any point/benefit).
Originally Posted by
mjordan123
3. Do I lose / gain value in the bike as a result (from a resale stand point)?
When buying a new bike, some models cost about $50 or $100 more for the triple version compared to the double version, but often they are the same price. For resale, I doubt it would matter - some people would not want to buy it if it has a triple on there, some people would not want to buy it if it has a double on there. If you sold it with the new double setup plus the old parts to convert it back to a triple, it might increase the value, but not by much.