OK, on my S3, I got a Di2 53/39 172 crank and on my P4 I got a Zipp Vumachronos 170 53/39. WTF do these numbers mean? I have no idea....Just took the advice of some bike pro.
I got 7 Dura Ace 7900 cassettes: 11-21, 11-23, 11-25. A buddy told me I need a 28 for a hilly road race so I'm gonna get one of those. Why? No idea.
I see that there are also available cassettes numbered 12-21, 12-23, etc.....
What's the diff between the "11s" and the "12s??"
How's an average shmoe like me supposed to decifer all these numbers???
(scratches head with total befuddlement)
Thanks again for your patience and input.