Specifically M525. Daughter’s bike has a M525 rear hub on it and the freehub has started slipping.
I bought a complete rear hub and planned to swap the new free hub onto the old hub and keep the bearings, axle and skewer as spares.
Only problem is the new hub is marked M525A.

Are parts interchangeable between an M525 hub and an M525A?

Should be fine.

As he said…. Did this a month or so ago. Hubs were absolutely identical… Apart from the letter “a”.

When you get the free hub off the body (don’t forget you will need an awkward size 11mm hex key) pop the seal off and flush out with gt85 or similar…. Lube up with some chain oil. My skipping hub kept going for another 1000 miles or so…. Until play in freehub bearing caused my chain to skip 4/5 gears at a time 😀

I thought it was a 12 mm hex bolt. Some are 10 mm.

525A is different, it’ll fit the hubshell, but you’ll need to use the 525A drive-side cones as the seals and their housing are different (new cones are a good idea anyway), and use the old cones on the non driveside as the new ones won’t mate with the old seal housing, and the new housing won’t fit into the old hubshell.

Cheers Coatesy, just done that. Works perfectly.