Hi has anyone fitted a Deore 11x51 11speed cassette to a GRX 810 di2, have been told not possible but I was told the same about an 11x46 and that worked no problem.
I can't see why it wouldn't depending on the length of dérailleur cage ... Buy from somewhere you know you can return to if it doesn't fit?
You may need an adapter.
https://www.sjscycles.co.uk/gear-spares/aluminum-rear-derailleur-hanger-ext...
