dura ace 9100 can't cross chain

[Rick]

From the same Friction Facts article:
"If you instead insist on staying in the big ring all the way up to the 28t cassette cog – thus putting the chain at an extreme angle – you might think that you’re going faster but you’re actually pushing about 0.75w more than necessary had you instead shifted to the 39-21t.

0.75W ??! Three full quarters of one Watt ?!?!

[BdaGhisallo]

From the same Friction Facts article:
"If you instead insist on staying in the big ring all the way up to the 28t cassette cog – thus putting the chain at an extreme angle – you might think that you’re going faster but you’re actually pushing about 0.75w more than necessary had you instead shifted to the 39-21t.

0.75W ??! Three full quarters of one Watt ?!?!

Say after me - 750 milliwatts. That sounds a lot bigger.

[Calnago]

Holy crap! Now that you put it in those terms I will for sure never use my upper 3 cogs again while in the big ring. Of course, by the time I drop my chain and shift two cogs at the back whoever I was trying to stay attached to will have a gap. Damn it. . If only I could have just shifted one little cog, so easy, yet so inefficient. Ha. Marginal losses.

[TobinHatesYou]

If you know you’re going to be shifting down to the small ring at some point on a climb, it’s simply better to do it beyond the 4th cog than beyond the 3rd cog. I’ve already stated on multiple past occasions that for small ramps, you may as well stay in the big ring even up to the 1st cog, but you continually only harp on specific quotes. Also one of the earlier points was that in the specific case of the SRAM 11-32t, it presents an opportunity to rev match with just two-clicks of the rear derailleur.

As for Rick, your use of small-small saps ~3 watts at an undisclosed rpm and resistance, all of which is going into unnecessary drivetrain wear. The logic of staying in the physically biggest gears as often as possible applies both ways. When shifting up to harder gears, you shift to the big ring earlier, like I said from 1x6 to 2x4–unless you know you’re going to be shifting back down soon after (specifics for Calnago.)

[Calnago]

Look, everyone here knows what is ideal and I think we are all fully aware of the pitfalls of cross chaining. But it’s done all time and whether one chooses to do it or not is very situationally dependent. I am constantly shifting both front and back simultaneously dependent on the conditions and where I want to end up a split second later, taking fully into account the road conditions ahead. You talk as if people here don’t get that. They do. But if you think I’m going to forego the most convenient shift (be it for reasons of performance, wear, the road ahead, etc) because Friction Facts says I might be giving up a milliwatt or two, then think again. The real world is like that sometimes.

The crossover points themselves can vary depending on the situation as well. That’s why I hate Synchroshift and it’s equivalents... because it defines (albeit user configurable) when those crossover points are. But those points can vary during a ride. I want full control of when I’m changing rings and also how many cogs I’m shifting at a time... 1,2, or 3 or whatever. However, any more than a simultaneous shift of the front rings and 3 cogs at the rear means I was just in a terribly wrong gear before even making that shift, so I generally will never be slamming more than 3 cogs at a time. Easy to do with Campy mechanical.

[Rick]

I really have no contention with anyone who really has a more efficient way to shift. The science seems to indicate that it is really more efficient, and gives less chain wear (although I am not sure how well that has been quantified.)
I am only saying that I cross-shift a lot, have been for a long time, it works for me, my derailleurs allow it when properly adjusted, and I have never really noticed any significant change in my chain-wear rates. ....and the loss of power seems small enough that it is beneath my priority of concerns. (Not puking or swallowing a lung is usually higher on my list of concerns.)
I stand guilty as charged as a watt-wasting; chain-wearing syncroshift denier! I honestly don't even know where the crossover point from big ring to little ring is. (partially because I switch cogsets a lot too) I just figure that when I am going fast I better be in the big ring and when I am going uphill I will probably need the small ring. I secretly admire anyone who can really make shifting theory work to any coherent shifting strategy !

[Calnago]

And that’s the point. Go with what works for you. I’m conscious of chainline for sure, and of course it’s smoother when straight. But really, I still want access to all combos at any time. Had a girlfriend once who just loved using the small/small. And she was a super strong rider. I always cringed when she would use that gear at any time let alone for just cruising along. Plus, when it came time for a new chain, you could be sure she needed a new cassette as well since the new chain would skip incessantly over the overused worn cog.