11speed mech comparability

mech help..

will a 1x 11 mech (m5100) work on a 2x 11 speed set up
I keep reading conflicting info..

TL:DR

I’m attempting to do someone a favour.

friend of the wife brought around her sons bike, he’d broken off the rear mech.

they’d got a new hanger but when i put the mech back on it was twisted beyond repair.

they’ve got a 1x mech to replace but will that work with the smaller rear cassette? I read you can’t adjust the b screw enough.
does it matter?

thanks in advance

If it’s SGS it should be ok, there’s two indexing marks on the top of the inner plate for the 51 and 46 tooth large cog. I’m working from memory though so I’ll get dressed and check in the workshop.

I’ll get dressed and check in the workshop

Now I will forever have you in my head as a naked guy sitting at a computer.

@thols I’m 64 too for extra “yuck”’ !  @MartinS the markings are for 51t but as it’s a 2X set up it should work. The tooth capacity of the SGS mech is 40 so add the teeth together for both big rings and then subtract the small rings (front and back) if the result is 40 or below then with an accurate chain length and some ‘b” screw fiddling it should work. Hope this helps, I’m a bit rusty so someone else may have a better idea but basically a longer cage is for taking up chain slack so 11-51 single ring or a double front with a smaller rear first gear should work. Good luck!

Thank you wheels..!

I’ll give it a try. Lad got an ex-hire bike that was meant to be serviced before it was sold.. I don’t think much was done to it!

he’s not actually that bothered with the double front and wanted it converting to 1x but if we get into new cassette, chain etc the cost will really go up. I’m going to raid. my (fairly extensive) collection of MTB stuffI I haven’t thrown out to see what I can donate but just in case I don’t have the correct stuff its good to know this. will probably work!

The trouble is 1x mechs are designed to move the jockey wheel away from the cassette as you change into the very large cogs. If you put it on a 2x setup, the gap between the cassette and top jockey wheel will be massive when in the big front cog otherwise it will crash in the small cog due to the change in chain length. There’s a very good reason they had to make 2 different cage geometries.