I’ve had my Shimano wheels (XT M785 29ers) less than a year and the freehub is humming really badly when freewheeling at speed – pulsing hum accompanied by movement in the cassette of a couple of mm up and down.

Pretty sure this is something that will have happened to people before, but anyone got any suggestions of fixes? Checked the cassette already, pulled the axle out, checked the bearings and re-greased, adjusted the cones, etc. I’m assuming I’m going to end up pulling the freehub off so have a 14mm Allen key on order, but if anyone’s got any suggestions that might reduce the time I spend staring blankly at the various bits when I pull it apart, I’d be glad to hear ’em!

What tune is it humming? May be a sign it’s bored and you need to go faster?

Since it only does it on freewheeling I took it as a sign that I needed to pedal more.

Pulsing hum… Could be Portishead or Massive Attack, I think.

Havent ridden a shimano freehubed wheel for years.
But they always used to develop a rumble along with a slight swaying of the cassette when freewheeling.

Which bit of the intro does it sound like?

[video]https://www.youtube.com/watch?v=6cW4TaEIGxM[/video]

The freehubs do tend to fail fairly suddenly and catastrophically so it’s probably worth having a cheapy compatible one (about a tenner) to hand for when it happens half an hour into a riding weekend.