I'm in the large chain ring accelerating for a climb... I start downshifting to maintain my cadence. When it becomes necessary to shift into the small chain ring, how do you avoid "spinning out" after shifting to that smaller chain ring? Do you upshift rear cogs before going to the smaller chain ring? Or do you shift to smaller chain ring - then upshift the rear derailleur? Or do you do both shifts simultaneously?

I feel like I'm losing too much momentum as I go from large chain ring to small chain ring on ascents... thanks for any tips.

First thing is to plan ahead and shift to the small ring before you absolutely have to.

I'm guessing you are using a compact double? If you shift early, before you're under full load, you'll be able to shift down at the front and up at the back simultaneously. If you're uncomfortable with that, I'd suggest shifting up at least one gear, maybe two, at the back a fraction before you downshift at the front.

This. Double shift.

Sounds like OP you are shifting down the cassette to the large end before shifting in front. That is intuitive but wrong. The two front rings are for different situations. Seeing a hill coming, you want to get onto your hill ring, the small one as soon as possible. Basicly what [MENTION=195034]chasm54[/MENTION] said. Up in back while it won't hurt you because you aren't climbing much yet, then rapidly after that down in front.

Simultaneously. Works when shifting front derailleur in either direction.

If before the hill, I will shift two rear cogs while shifting to the small ring. If already on the hill and it is steep and I am slowing fast, maybe just one rear cog.

Drop off of the big ring and shift down one or two on the cassette as the climb starts and before need to lean into it. Now you are still in the same cadence but with the lower range available to you enter the climb

This is where DI2 shines. The double downshift is as clean, fast and drama free as can be. Tap the left down one while tap or press and hold right depending on how sharp the rise is. No muss no fuss no drops.

+1 This will also prevent dropping the chain when you shift to the small ring while on a large cog. With a little more detail: Before starting the climb, shift to the small ring then up shift to a comfortable gear in the rear. As you climb the hill, shift to lower gears as needed.

Double shift here as well. Hard push on the left, quick double click on the right (SRAM shifters).

This is the way it is done

Similarly to the aforementioned......I simultaneously double-click for the rear and click the front......HOWEVER.....this is where I had to get used to something new.

For those with new Shimano 11 speed setups......the trim setup is different than it used to be. The click to drop to small chainring can sometimes be inhibited by an unintentional trim adjustment in the big ring. Trims now start "outermost" position whereas they used to be "innermost", requiring a half-click to drop inboard. (Sometimes if I know a hill's gonna come anyway, I'll already hit the 1-click trim adjust in the large ring to get ready to go down into the small ring).

If you've got a 9000, 6800 or 5800 you know what I'm talking about. As such, I've gotten pretty quick at my clicks regardless just for that very reason. I can sound like an old electric typewriter if I get in a pinch....(Click-ka-click-click--Click).....and off I go hoping nobody saw me fumble the trim click.