Am I missing something? Why not just get a 9 speed 12-28 cassette?
Yes
Firstly, there is no 12-28 9spd cassette that I’m aware of. There is a 12-27 which gives decent ratio gaps but still not as low as I’d like, and there is an 11-28 which gives too big ratio gaps, an 11T which is totally useless to me, and still doesn’t go as low as I’d like.
Basically, I can manage fine up any “normal” hills with the 34/25 bottom gear, but when you’re faced with a couple of climbs round this way, one of which averages 17% for nearly a mile and has parts of it quite a bit steeper than 25%, it is a bloody battle when you’re box fresh, but the 100 miler I’m doing in a few weeks goes up it when you’ve already got almost 70 miles in your legs!
Was thinking if my current Tiagra gear is worth close to £200, for the price Merlin are doing a full 10spd Tiagra setup (and you can get a nice 12-30 cassette with that!), it would make sense to upgrade… Certainly way more so than the price of a triple chainset, long cage rear mech, triple front mech and a new 9spd chain would cost.