Yo!
Wise folks of TriTalk.
If I whack an 11sp rear mech onto my TT bike, can I just change the front 10sp shifter to friction based (the non click, non indexed one) and it’ll work?
Obvs put an 11sp cassette and chain on, too.
CBA swapping cassettes between wheels anymore 
I’d possibly say not that the range it has might not be enough. Could try it though.
That’s the thing, I don’t wanna swap it all over only to find it doesn’t work!
I’ve had 10sp cassette and hub working on 11sp before (remove 14T cog, spacer, adjust limit screw) which was easy 
Just a bit annoying having an 11sp bike and botching it to 10sp. I need all the gears I can get my hands on these days
I reckon you’ll get away with it.
Pita and a complete waste of time if it doesn’t work though
Can’t you get a shifter? Shouldn’t cost much on eBay or somewhere.
The cassette width is only a few mm wider in 11speed I believe, and there’s no chance there’s not the range - the width between the wheel and the frame doesn’t change between 10 and 11, and the derailleur’s are perfectly capable of throwing themselves into the spokes.
I have an 11sp RD n my box o’bits.
I just lack time at the minute 
Like Jim says, I doubt you even need to change the derailleur
Just the chain and cassette
Hmm…the mighty con of the bike industry!!!
Ha ha ha 
11 sp cages are narrower…slightly…so you can’t go the other way i think…but am not sure about the jockey wheels…
alignment an issue perhaps?