This post does kinda have compact crank content**...
I've been using Di2 for about 2 years now. My battery has never lasted as long as some people claim, maybe because I probably shift more than average. I charge every 4-6 weeks.
But three times now I have accidentally let it get low enough so that I lost shifting on the front derailleur. The problem is that I think the blinkie scaling is off. When it goes to blinking green you're supposed to have about half the power left. But when mine starts to blink green it goes to blinking red and then low power mode pretty quickly.
Before a hard, hilly century ride last Sunday I noticed that it was on blinking green. I was out of town so I couldn't charge up. About 80 miles into the ride I lost the use of the front derailleur. It was stuck on the small chain ring. With the compact crank** that meant I could only pedal up to about 20 or 21 mph. Then I had to coast. Also because I was in low-battery mode I had to "ration" the number of times I shifted on the RD so I wouldn't run the battery down altogether, so I ended up being in too hard or too easy of a gear much of the time.
I wouldn't go back to a bike without electronic shifting, but it's not 100% trouble-free either.
2009 Cervelo R3SL TdF Edition, Ultegra Di2
2011 Cervelo R5, DA Di2
Get sheldon style 10lb wheel dynamo with DI2
That, or perhaps an 800gram ventless solar paneled helmet should be standard equipment.
I'm curious, what is the running voltage on DI2?
If its Lithium Ion recharge, am assuming 3.6-3.7.
It'd be so easy to double your milliampH with 18650 battery in stem.
These batteries, slightly larger than AA, will fit damn near anywhere. Seatpost, handlebars, stem, etc etc
Not sure how the Di2 thing got woven in...but for those considering changing their gearing via either cassette and/or crank, the following link is a good read for Campy guys. I believe there is an effort to reduce rear derailleur complexity by melding short and mid cage length with Shimano and Sram as more pie plate cassettes find their way onto road bikes spawned from the mtb crowd, but Campy sticks with three rear derailleur cage lengths. Since many of us run a short cage, the question is, how much chain wrap a short cage Campy derailleur can tolerate...like I have for example as I change to a 13-29 10 speed cassette in back. Chain wrap is defined by the difference in cassette spacing + difference in chain ring teeth in front. For example, initially I will likely run a 50/38 with 13-29. Quick math yields 12 + 16 = 28. Campy conservatively specs 27 as max chain wrap for their short cage derailleur. In other words it works with judicious chain sizing. (Campy tends to be conservative with component compatibility) One cyclist in the link below has run a 30 tooth aggregate spread without issue with Campy short cage. I may go there as I am considering a 50-36 with 13-29 = 30 tooth chain wrap on the button. This set up will avert the dreaded 50/34 hole in front shifting and provide nice short gear inches for climbing the steep stuff with toasted legs at the end of a long ride. Good read for those interested: http://forums.roadbikereview.com/campagnolo/13-29-short-cage-derailleur-131507.html
Capacity is only somewhat important. Like you said it is usually conservatively listed, and it only affects the 1-3 smallest small/small combos which in general should be avoided anyways.
Right now the 52/36 with 12/28 on my tarmac is just to much gearing going up hills for me, I've be thinking of going with a 105 50/34 to ditch the FSA Gossamer crank.
Just not sure how much real world lower I'll gain
[QUOTE=redlude97;15670715]how is the 19 not in the middle of the cassette? You have 4 lower gears than that.
3.....22, 25, 28
I put a 42/28 on mine a few weeks ago and so far I haven't missed having 50 or 52 even once.
However, I don't race, and, around these parts, it counts as a flat ride if you don't have to climb anything steeper than 6%.
I do. I was a hater for a while, but once I made the switch, I am not looking back. I run a 11-25 or 11-26 on the back, depending on the wheelset. I find the 50t perfect for riding in the middle of the cassette at my normal cruising speeds. A 34t provides as low of a gear as I could ask for. I can always put a 11-28t on the back if I'm looking at sustained steep climbing. Moving to a flatter area next year and might switch to a 50/36.
On Saturday's group ride, for the first time, I found myself wishing I had a bigger gear than 50-11. Big bunch hammering along a long stretch with a tailwind and slight downhill grade, we were hitting 36mph and I kept pushing my gear lever something bigger. I think my cadence was around 110. Other than that though, I like it: I can use the big ring for most of a ride, only switching to the little ring for steeper stuff.