Help with Switch to Compact Cranks
Hello!
I'm hoping I can get some guru help here. The bike I just bought came with standard cranks and a 12-23 cassette. I learned pretty quick yesterday during a long ride outside that it ain't gonna cut it on the HIM course I'm doing in August. Even smallish hills require mucho watts to get over. I want to just go ahead and switch to compact, but I've got some questions that I'm hoping to get some advice on. I've read up as much as I could in the last couple days on this here on the wiki and related posts, but still have some unanswered questions.
I currently have full Dura-Ace 7900 components but want to keep the cost of switching down. So question 1 is can I go with an Ultegra 6750 crankset and cassette? Will it work with the Dura-Ace derailleurs? I sure hope so.
Q2: Assuming Ultegra works, do I need a different Bottom Bracket? Assuming I do, are cranksets usually bundled with BB's or do I have to buy separate??
Q3: The reading on the wiki seems to indicate that 11-26 is the better cassette b/c it gives you the lowest gear option and higher gear option. Im leaning towards that one, but wondering if there's a negative to that choice over the 12-25 or even 12-27.
Thanks in advance for any help with this!!
Comments
Q2 - Should not need new BB. No, the cranks I bought did not have BB with them.
Q3 - I like my 12x27. I spin out at 34mph+, so that is probably a pretty good time to coast down the hills. That being said, I am getting (for my B-Day) an 11x28. I want to see how different the cadence gaps are, but I don't expect them to be a problem. Like voting in Chicago, I shift early and often.
The only negative to topping out at a 26 is slightly lower cadence for the same power in a climb. How are you at keeping watts constant and at what you want at a low cadence?
That was HILARIOUS!!!
Ultegra will work fine, as will 105, the BB does not need to be changed if you stay with a Shimano crank. A SRAM crankset will need a different BB.
You will probably need to LOWER the FD, if you have if professionally installed (by an LBS), they'll know what to do.
I'd worry more about the largest cog over the smallest. You're going to end up with an 11 or 12 small cog which unless you're a super-powerful rider, you will only end up using this cog right before you "spinout" on a downhill.
That leaves the large cog to consider - 25, 26, 27 or 28 - I'd get two if you can afford it, pick say a 25 and a 27 and swap them as as the course necessitates. and yes an 11-26 is a good choice if you're only buying one.
I also agree with Cary, cassette flexibility is a great tool for course specifics!
So I think I'll go with a Ultegra 6750 crank (no new BB needed) and a 11-26 cassette for starters and build up the arsenal with other cassettes later. So am I mistaken that Shimano doesn't make a 11-26 and I have to get a SRAM? They are compatible? I see the SRAM OG 1070 (Rival) going for around $60 to $80.
@ Scott, I got the bike used so I can't do an exchange. I'll probably try to sell the Dura Ace crank on ebay to help offset the cost.
I prefer sram cassettes with my shimano shifters.
26-11 is a good cassette. I use it for all of the mountain riding I do at home. I'm rarely on the flats long enough to notice the cadence gap, I like the 26 for the long climbs and the 11 for the long downhills. I spin out at about 41-42mph. However, you may want to get or borrow a 25-12, as the cadence gap will be less and I doubt you'll need the 11t. You'll spin out the 12t at about 38mph.