Originally Posted by
Kontact
Personally, I would use a short cage derailleur and leave the chain long enough that the small/small is slack. That's how we ran short cage Deore XT derailleurs with triples on MTBs in the early '90s. It won't break anything and the small/small with a granny is easy to avoid.
After experiencing Tiagra GS, I also can say that maybe SS works better. However, Shimano manual lists SS as 33T capacity (vs my 34T) and 16T max front difference (vs. my 20T). Furthermore, triple is not mentioned for SS, but it is for GS. Overall, the manual says that GS meets all my requirements, while SS misses 3 requirements. Nobody would ever choose SS over GS for my setup, according to the manual. The conclusion is that for smaller cassettes, triple and large capacity, any Tiagra 4700 does not work, although Shimano claims it does. It does, in fact, but with low (hesitating) performance.