vol

Suppose your front gear is at 2, rear gear at 4. Now you want to change front to 3 and rear to 5, is it better to switch the two at the same moment, or one at a time (which one first?)? Considering all factors including any harm done to the chain.

Jeff Wills

I do double-shifting all the time, but it's usually to downshift half a step (such as front 3 to 2, rear 6 to 7). I haven't seen anything odd in terms of wear and tear.

Bicycle chains are amazingly strong and durable. It'll take much more than shifting both derailleurs at once to damage one.

Northwestrider

No problem shifting both at the same time. It'll work fine.

vol

Thanks. Should one avoid switching gear too frequently, such as every time you are going to stop (lower the gear for easy start)?

dabac

They're there to be used, so use them. Drivetrain parts last long enough as it is, there's really no need to "save" them like that, particularly not at the cost of usefullness and sensible/safe trafic behaviour.
Keeping the drivetrain reasonably clean and lubed, easing up on the pedal pressure when shifting, and avoiding cross-chaining will do much more for extending drivetrain life than trying to reduce the number of shifts.

TugaDude

+1, great answer. It is always a good idea to downshift at a stop. I think it is funny to see people stop and then have to stand on their cranks to get going, albeit slowly, back into traffic.

bradtx

vol, Changing gears at both ends at the same time used to be SOP back in the 10S (2X5) days. Just don't make really big shifts, like sweeping across the entire cassette or freewheel. For a stop and go type of ride, like a commute, dowshifting both ends prior to stopping is no big deal, I don't usually upshift both ends at the same time when accelerating, but that's just me.

You won't hurt a thing shifting gears, the bike works for you, not the other way around.

Brad

2manybikes

The system is not designed to control that much chain slack at one time. Just because it can be done does not mean it should be done. The chances of damage go way up it you do it. If you hit a bump or have a panic stop you may damge the frame, parts, or you. You could lock the cranks by getting the chain wedged between the crank and the frame..

rm -rf

I have a compact crank, with 50 and 34 chainrings. So when the road starts going uphill, I need to shift from 50 to 34. Then the cogs in the back are in a too-easy gear, so I want to shift them about 2 or 3 cogs smaller.

I usually shift the front first, then the back, instead of simultaneously. There's less loose chain that could mis-shift that way. But the back shift still happens within one pedal revolution. ( I'll shift both at once sometimes, and I can't remember the last time it didn't shift correctly. )

I'll even shift a rear cog for only a couple of pedal revolutions if there's a small change in the road grade, then shift again. It won't wear out the chain.

rydabent

brad +1

Yes back before 1985 or so, if you read any cycling book, they always talked about half step gears and shifting them. Maybe for professional racers it was a good thing, but for recreational cyclist that was over thinking gears in my opinion. These days with 24 to 30 gears available double shifting is probably even less necessary.

Will double shifting hurt----no probably not. But still I would shift one at a time.

Homebrew01

Your bike must be very delicate.

I double shift often. Especially when approaching a hill while in the big ring. Drop to the small ring, while dropping down 2-3 cogs in the back to end up in a slightly lower gear, and ready for more down shifting as it gets steeper.

fietsbob

... back when shifters were on the down tube you could do that with one hand.