Road Cycling - Choosing a Cassette - first road bike

Hi I'm a mountain biker looking to buy my first road bike and I’m definitely going to get a triple. When I first got my mtb I got the shop to swap the double to a triple but left the original cassette which made the lowest gearings on the granny useless. I don’t want the same thing to happen on my road bike.

I going to get the shimano ultegra 6500 groupo (9 speed triple of course) but I need help choosing a well matched cassette. After searching the forums about cassettes finding mostly advise for people with a double and reading the double vs triple posts it seems to me that many people who have triples use the same cassette they would use with a double meaning that they almost never use the granny.

For a triple it seems logical that 11-21 (11, 12, 13, 14, 15, 16, 17, 19, 21) or a 12-21 (12, 13, 14, 15, 16, 17, 18, 19, 21) cassette would offer the smoothest shifting over its entire range and still allow the granny to be low enough to cover the hills. Obviously I wouldn’t use the highest or lowest setting possible very often (or at all) but they would be there if I did. I couldn’t find anything about the compatibility of the various ultegra cassettes but I assume they are all interchangeable.

Sorry if I rambled but I have recently become obsessed with getting a road bike and I have no idea if my reasoning is absurd.

Summary Question: Would it make sense (or technically advisable) to use a 11-21 or a 12-21 cassette with a shimano ultegra 6500 with a triple for hill climbs and centuries? Are there any other ratios that you would recommend instead?

I wouldn't personally use a triple but if I did I'd treat it as a bail-out gear and concentrate on a well-geared double set-up. In that case a 12-23 will handle most of your riding. 39x23 (for example) will get you up a pretty steep hill. You'd want to drop to the granny ring for a prolonged steep ascent maybe...

FWIW, I ride with 39/53 and 13-23 (8-sp) and when I'm fit there's no hill that I can't get up without a bit of grunting. In the summer I switch to a 12-21 but go back to the 13-23 if I'm doing rides with hills steeper than 5% and longer than a few km.

I'd agree with you, Simple. If you're going to get a triple, you may as well get an 11-21 or 12-21 cassette so you can actually use all the gears. I'd get the 12-21 - gearing will be high enough without the 11. Your lowest gear combo will still be plenty low enough for most terrain, and fine for the majority of organized rides etc (assuming you are reasonably fit). You could always buy a larger spaced cassette (12-25) and the cassette changing tools so you could change it if you ever do any serious climbing.

FWIW, I run a double (53-39) with either a 12-23 or 12-27 cassette depending on season/terrain.