Originally Posted by
unterhausen
you can use a 34 on Ultegra. The only trick is to get a cassette. SRAM works. You have to screw the limit screw back a little
I've used a 11-32 on an Ultegra GS. I'm not sure that a 34 would work an many road bikes, the length of the hanger is part of the issue. A 30 will work with all road derailleurs and frames without concern.
I also like the spacing of the 12-30. The Apex 11-32 has a wider range, but you lose the 14T cog. The jumps in cadence can get noticed with the Apex 11-32, especially on flat routes with some wind to push against. a MTB cassette, like a 11-34, has even larger jumps between the gears.
I'm running a 50, 39 & 26 triple with a 12-27t cassette on my CX/commuter bike/do-it-all bike. The 12-30t cassette & 50, 39 & 26 triple should give me a huge range without the need for a MTB rear derailleur. I'm replacing a worn chain & cassette soon, timing could not be better.