Get Shimano Di2 at Amazon.com.
Update 25 May 2016: it turns out that DuraAce does support an Ultegra 11-32 cassette.
I had been running the original DuraAce Di2 10-speed on my Moots Vamoots RSL. Finally I scraped together the money for Shimano Di2 11-speed . There were several motivations, in this order:
- I wanted the 11-32 cassette option (32-tooth cog) that is possible with Di2 Ultegra. Because on 10% to 26% grades of the Eastern Sierra, that 32 cog will be my best friend. Especially after climbing 10,000' or more already. An 11-28 is fine for most stuff or for shorter efforts, but for Alta Alpina 8 Pass Challenge and the Everest Challenge or the 26% grade of eastern Sonora Pass, that 32 cog will be lovely.
- The 11 speed cassette means a tighter spacing when using 11-28 cog (less gappy in gear ratios in the last 3 cogs, if it weren’t for hills I’d use an 11-25 cassette).
- The Ultegra and DuraAce derailleurs are plug-compatible, and thus the same bike and wheels are more versatile with a derailleur and cog swap (chain may have to be replaced if switching to the shorter-cage DuraAce derailleur, but the Ultegra handles a 28 or 32 cassette). In the winter, I can run the DuraAce derailleur with the 11-28 for tighter spacing; I don’t need the 32.
- The 10-speed Di2 parts can be used for spare parts for on my Moots PsychloX RSL, which has 10-speed Di2, it’s now a sort of 2nd road bike that sees only a little dirt. With the original 10-speed Di2 getting harder and harder to find, this gives me a backup set.
- My left Di2 shifter has been intermittently failing to shift, and I did not want buy a new 10-speed shifter.
The 11-32 Ultegra cassette delivers an entire extra gear (32 cog), but matches the last two cogs of the DuraAce 11-28 with its 25, 28 cogs. So it’s like getting three gears instead of two when climbing the steep stuff.
With a 50 X 34 compact double crankset, the gear ratios are 50:25, 50:28, 50:32, or
DuraAce 11-1828 11,12,13,14,15,17,19,21,23,25,28
Ultegra: 11-32: 11-12-13-14-16-18-20-22-25-28-32
Weights accurate to the gram.
- Shimano DuraAce Di2 FD-9070 front derailleur: 107 g (vs 119g for orig 10-speed)
- Shimano DuraAce Di2 RD-9070 rear derailleur: 215 g (vs 222g for orig 10-speed)
- Shimano Ultegra 6870 Di2 RD-6870 long cage derailleur: 266 g
- Shimano DuraAce Di2 RD-9070 11-28 cassette: 195 g (with lock ring)
- Shimano Ultegra 6800 11-32 speed cassette: 284 g (with lock ring)
- Shimano DuraAce Di2 9070 Shift/Brake Lever (set): 236 g (vs 242g for orig 10-speed)
- Shimano DuraAce CN-HG-900-11 chain: 256 g
The weight penalty for the 32-cog Ultegra setup vs 28-cog DuraAce setup is thus (266-215) + (284-195) = 140 grams + some extra chain weight— call it 160 grams, or about 1/3 pound. Undesirable (why is there no DuraAce 32 cog support?), but a modest penalty to gain an extra gear on steep climbs to save the quads.