11s derailleur on 12s drivetrain

[Seph]

I have an MTB that i use as secondary bike.
Since it has 10s i want to upgrade to 12s and remove a bit of weight whiteout breaking the bank.
Somewhere i read that the 10s derailleur have the same pulling ratio as 12s, the only difference is the shifter and the derailleur's hanger extension just the help it reach the last big sprocket.

I know it sound crazy but do you guys think is doable? Or is a bad idea?

My model is the RD-M5120-SGS/RD-M4120-SGS full compatible with 2x10/11s, with right crank spacers probably with 1x setup too.




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[js]

Even if the derailleur's cable pull ratios are the same, those derailleurs have a 46t max for rear cogs. Unless you're planning to run it with SRAM X-plore or XTR race 12s cassette (both of which seem to counter to what I assume is the goal of a cheaper way to upgrade to 12s and miss out the range increase that would normally be the biggest benefit of 12s), then I don't see how you'd get it to work, as you won't have the chain wrap or range in the parallelogram to use a 50T cog or bigger.

[Seph]

Even if the derailleur's cable pull ratios are the same, those derailleurs have a 46t max for rear cogs. Unless you're planning to run it with SRAM X-plore or XTR race 12s cassette (both of which seem to counter to what I assume is the goal of a cheaper way to upgrade to 12s and miss out the range increase that would normally be the biggest benefit of 12s), then I don't see how you'd get it to work, as you won't have the chain wrap or range in the parallelogram to use a 50T cog or bigger.

Thanks

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