Originally Posted by
Wits_Of_Fury
I'm finally building the commuter I've talked about for two and a half years. It's going to be a Long Haul Trucker frame. My original plan was to upgrade my CAAD10 to Ultegra 6700 and slap the 105 on this one. The main compatibility issue I have with that is the Ultegra triple crank on the LHT (FSA compact double crank is BB30 and must stay with the CAAD) with the 105 double shifters and vice versa. I want STIs on my LHT, as I'll be navigating the streets of San Francisco and for personal preference.
Can I get away with a double on the LHT? Will a 52/39/30 give me that much more than a 52/34 when weighted down and likely going uphill? And could I even put the 105 shifters with an Ultegra compact double?
Double if you can spin 39x21, 23, or 25/26 up most of the hills you can encounter and manage the rest depending on your starting cog preference and cog count.
That could be
xx-39 x 11-21 10 cogs
xx-39 x 11-23 11 cogs
xx-39 x 12-23 10 cogs
xx-39 x 12-25 11 cogs
xx-39 x 13-26 10 cogs
xx-39 x 14-23 10 cogs
xx-39 x 14-25 10 cogs
where xx could be a 53 or 50 depending on taste.
Triple otherwise. Anything else compromises gear spacing and/or the amount of front shifting you do.
Note that
1. 74mm BCD road triples take granny rings down to 24T.
2. Middle x small cog has a better chain line than small x second on a double
While you can often match the range of a triple using a compact double
50-34 x 12-13-15-17-19-21-23-25-28-32
53-39-26 x 13-14-15-16-17-18-19-21-23-26
the jumps will be a lot coarser on flat ground and you'll have to shift to the big ring in a lot more situations (34x13 is like 39x15).