My rear wheel has recently started to get quite noisy when it spins (Shimano XT 6 bolt hub). It's as if I can hear the bearings – when I spin the front wheel it's silent, so that makes me think something is wrong.

I cleaned and regreased it but I still get the same problem – what's going on? Is my cleaning/greasing routine just too rubbish? FWIW I am using some general purpose grease that claims it is good for bearings on the tin…

Recently I noticed an intermittent creak from my bike too, which happened when free-wheeling. This supposedly means it can't be the mech or BB, so I wondered if that could be hub-related too.

Do I need new bearings?

yes

probably the free-hub body if you've done the main bearings.

Poss either the drive bearings (most probably) or the freehuby body bearings. Shimano use freebearings – can get them cheap from LBS – poss easiest or you can get them online – but if your not happy with it just let your LBS do it i.e. freehub body bearings 🙂

My old LX hubs I replaced the bearings as they were scored but made little difference as the races were also scored. I'd just replace all the bearings and see – while you are there.

Bearings likely need replacing. Possibly the cones in the hub are gone, but less likely. Worst case is the races are pitted. Try the bearings first, and while you have the cones out take a good look at the surfaces for any deformation or pitting. It doesn't take a lot to make for rough turning of the axle. Thankfully cones on Shimano hubs are easily replaced, just make sure you get the right ones.

Oh, as above, you'll easily be able to isolate whether it is the hub bearings or the freehub bearings by determining whether the roughness comes only when the freewheel mechanism is activated. From your previous description I assumed the roughness was in the hub bearing.

Thanks for the help guys. I didn't inspect the cones thoroughly, but they seemed OK. Will do so again next time…

Here is the schematic: http://techdocs.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/FH/EV-FH-M756-2099A_v1_m56577569830608935.pdf

The bearings are apparently 1/4" steel. Where is a good place to buy replacements from? Can I (should I) get stainless bearings?

I suppose it would make sense to pack the freehub with grease too while I am at it…

P.S The hubs have only been used ~12 months!

You need a special tool to grease the freehub body, though it may be beyond saving. It sounds like you'll need cones as well as bearings and possibly cups. A cheap way to get them all is to buy a new hub.

The hub only needs one proper soaking to start corroding internally. Shimano hubs DO need regular servicing.

Ok… well I will try replacing the bearings first before going the route of a new hub. Thanks all!

Poppa, I have just had the same problem with the same hub, it's not quite a year old!

I found it was only on the drive side, the other side is like new still. I cleaned up the come which was pitted with emery paper but couldn't do the race as you can't really get to it. For now i have put the same balls back in but will replace them when i find a supplier. It now turns fairly well on the bike but feels really rough when spinning in my hands.

There was a thread on here a while back about the lack of grease in new XT hubs, i should probably have paid more attention then.

My drive-side bearings were worse than the non drive-side both times I opened it up. I think the sealing on the drive-side isn't as good to be honest.

UPDATE: I think it's the freehub. If I rotate the pedals in a high gear I don't get the sound until I stop rotating, if that makes sense…