I've got an XT M725 Octalink chainset (Hollowtech 1). I've heard that there are some compatability issues between Hollowtech 1 and 11 chainsets (something about tabs). Can I fit a 44 tooth, 104 bcd, 4 arm chainring designed for a Hollowtech 11 crankset to a Hollowtech 1 chainset (again, 4 bolt, 104mm bcd)?

Yes, although I'd check the M725 thing, I can think of M700 and M730, neither of which were Hollowtech. Also… bear in mind both are 8 speed, and all the newer ones are 9 speed, shouldn't matter too much though.

If you've got M750 (Hollowtech, not HT2) then it will definitely be absolutely fine.

Thanks, that's good to know. Are all HT1 & HT11 chainrings interchangeable? The XT M752 is 9 speed by the way.

Regarding the tabs: some granny rings meant for old Octalink / ISIS / square taper BBs used to have them on the inside to try and stop the chain wedging horribly when it fell off. Those rings don't work with modern external BBs, but there's no problem the other way around.

Otherwise 4-bolt chainrings are generally all compatible, except for XTRs and the current XT M770 rings which are slightly thicker (I think). I've mixed and matched Shimano, Raceface, FSA, Middleburn and Aerozine rings in the past. Middle ring tolerances are sometimes a bit tight but have always gone on with a little persuasion 😉

Yes, the M752 is both Hollowtech and 9 speed, but that's not what you said you had 🙂

Any rings will fit though, the way the cranks/bottom bracket attach does not effect the chainrings! At the very worst you'll have to file them very slightly.

Ah, a typo, sorry about that, yes it's a M752.