Shimano 1 x 10 with a 45t range expander?

Want to run a wider range on my 1 x 10 Shimano XT set up than the current 11 – 42 but I dont want the expense of new 11 speed shifter, chain and cassette. So can I use an 11 speed 45t range expander instead?

[*]I understand that 11 speed Shimano mechs work upto 45t and will index correctly on 10 speed. Is that true?[/*]
[*]Will an 11 speed 45t work OK with a 10 speed cassette or is there some kind of offset going on to get the additional sprocket onto the freehub?[/*]

And yes I know – I should man up, just use a close ratio road cassette, singlespeed etc etc. And yes 2 x 10 is better (its what I normally use) but this is for a Fat bike where I dont have clearance with the large rear tyre and a 2 x system. Cheers :D

I’ve “downgraded” my XT 11 speed cassette back to a XT 10 speed + 40T expander and it indexes correctly with the M8000 shifter and mech and NX 11 speed chain.

So I’d guess because the 11 speed GS mech will reach to a 46T then you’ll be fine with a 45T that’s meant to extend a 10s cassette (I don’t know of any 45Ts for 10s though, only 42T expanders).

I chose not to use a 42T on my downgrade because I was making it lighter by using the older 10s XT cassette and I can hardly notice 2T.