cohophysh

Hi,
I have been reading with intrest about compact cranks but have a few specific questions. Here is my current set up: All ultegra, octalink triple in the front and 9 in the back. Here are my Q's.
1) It appears, although opinions vary, that the 12-25 cassette is probably the best, now is that a 9 gear cassette or 10? I assume there is more combinations with a 10.
2) Do I have to replace my STI front DR, remember I have a triple now
3) Do the compact cranks fit octalink or do I need a new BB?
4) If I were to by a 10 speed cassette would I need to change out the splines on the hub, remembering I have a 9 speed now

thanks for your responses

JiveTurkey

1) 12-25 is available in both 9 or 10-speed.

2) The front derailleur should work fine. They're pretty much the same as a double except it has an extended inner cage plate. As long as it does not interfere with the inner chainring, which I don't imagine it would, it will work the same as a double would.

3) In general, you need to replace the bottom bracket when you replace the crank because they need to match (both in the interface system and the spindle length)--chances are your old BB won't work ideally (or at all) with the new crank. BBs are much cheaper than cranks anyway, so get the crank you want and match the BB.

4) 10-spd Shimano-cpmpatible cassettes are actually slightly narrower than 9-spd. You'll need the very thin (~1mm) spacer that should come with the 10-speed cassette. Remember, you also need a new chain and shifters if you go to a 10-speed cassette, but everything else should work fine.

TallRider

1. whatever gets you the gear range you want and are comfortable with is best - people want a wide enough gearing range while also not having too large of jumps between cassette cogs in terms of tooth number. The balance you want to strike between these factors is will determine your cassette.
2. road triple FD will work fine on a double, compact or not, it will just weigh a little more than it has to
3. there are lots of compact cranks out there, with various BB compatibility designs. I believe Ritchey made one that took an Octalink BB, although I'm pretty sure this is no longer in production, you might be able to find one out there. But even in that case, you'd need a different Octalink BB (with a shorter spindle) because you'd be using a double crank
4. 10 speed cassette will require new shifters, but will fit just fine on your 9-speed hub as JiveTurkey noted.

I'd say, if you want a compact crank, get one and the BB that's designed for it (and sell your crank and BB on eBay as a package). Don't worry about 10-speed as it's an expensive upgrade - shifters, chain, cassette, possibly front derailer though probably not. If you really want a 10-speed bike with compact crank, it might be cheaper just to sell your bike and get a new one.

cohophysh

thanks for the input