Originally Posted by
lem0ndrider
Thanks for the information. Would it be prudent then, to change my 52/42 to a 50/34?.
No. The 34 also requires a 110mm bolt circle diameter while most road triples are 130mm for the outer rings.
I don't use the 30 anymore and replacing the whole crank seems expensive.
That's most likely because you have a monstrous rear cassette with pie plate sized cogs spaced far apart. You need to consider both ends when contemplating gearing changes. Both spacing, when you'll need to change rings, and total range are all significant.
Get a tighter cassette. 12-23 (or maybe 14-23, or maybe 13-26 - it's more ambiguous) would be my choice in 10 cogs, 13-23 or 12-21 in 9, and 13-21 in 8.
Assuming 10 cogs you're better off with the triple unless you can spin a 39x21 or 23 up almost everything you'll encounter (depending on whether you want an 11 or 12 starting cog) and manage everything else. With 9 cogs you can have a 19 or 21.
While you can get close to the same range using a compact double and road triple, with a tight cogset the former means you'll be shifting the front derailleur a lot (over ten times more often) more with five cog changes in back to get to the next gear. Having run 50-34 x 13-23 9 speed (because it had the same range as 50-40-30x13-21 8 speed and two rings are better than three) where I shifted from 50x21 to 34x15 (five cogs away) on the small ring slowing below 17 MPH on a false flat up and back to 50x19 from 34x14 after speeding up past 19 MPH (that happens _a lot_) I advise against it (with a triple you can ride your middle ring for most flattish solo efforts).