Di2 (Page 2)

OK- so let's say it's a hilly race, and you get on the bullhorns for climbing quite often.  And let's say that you need to shift 100 times (not that many really) and it takes 0.6 sec each time.  So, you spend 60 seconds (1 min) moving your arms in order to shift.  You didn't exactly lose 1 min.  You were still moving and pedaling during that period of time.  So, perhaps your efficiency went to 60% of what it would have been.  so, for 1 min during a 1 hour race, you lost 40% of your power.  So, you went from 200W to 120W.  So- I put that power drop into bike calculator while climbing a 9% grade, and it added 26 seconds to the time.  If you're good, and can keep your power up to 90% (180W) while moving your hands, it still costs 8 seconds.

Now that I've got a power meter - I'm seeing a real difference in my power output between the hoods and the aerobars.  As best I can tell, my FTP drops 10 to 20 watts going from the hoods to aero.  So, any steep climb where my speed is about 12mph or slower, I'm on the hoods.  sometimes I find myself shifting while I transition my hands, with one hand shifting from the aerobar and the other shifting as it's grabbing a hood.  It becomes second nature after a while.

If you live in the flat land- perhaps this would have little advantage for you.  me- I never stop shifting.  My bike has 20 speeds and I use them ALL on every ride.

I rode a bike with the DI2 system at an Endurance show last spring. Definitely a game changer. Shift anywhere, anytime effortlessly without worrying about jamming the chain or popping it off, completely self-trimming. As stated for Tri bikes, suddenly you can use your Tri/TT bike for group rides and be able to brake and shift without reaching for the bars. Read the reviews. This system is ultra-reliable. There are a lot of guys using it in the Tour and most other races without issue. If you've noticed, when there is a mechanical issue (which there will always be and has always been) the fix with the DI2 is much simpler. A broken cable or out of adjustment cable leads to a bike change. 

Campy also has an electronic transmission out. More or less identical to the Shimano. The only difference is you can hold the buttons on the Campy down and the chain just glides across the gears. SRAM says they are never going electronic. Sure they aren't. That means they just haven't figured it out yet.

Also, I saw that Shimano is now offering the Ultegra in DI2 for TT/Tri bikes. At least, the new Cannondale Slice features it. That oughta chop a couple thousand off the price.

Well now, that's not quite accurate.  The Campy system has a completely different feel to it.  They've maintained a tactile feel to their shifting, I found it much easier to time my shifts because of that.  

I'll defer to you on that. I didn't get to ride the Campy system. Just played with it on a trainer. It seems like the Campy system is not real widely used which is too bad. I'm planning on going all-in on a new Tri bike this fall and it will have one of the electronic transmissions. I'd love to ride the Campy variety before buying. Any idea what cost is vs. the DI2? I assume similar in price to the Dura Ace setup.