Shimano freehub screw loosens

desweller

Afternoon all

Following replacing my (Shimano) freehub body in February the hollow screw came loose and caused the bearing to lock up. I figured I'd just not put enough torque into it and applied a bit more when I reassembled the hub (and a dab of loctite for good measure).

Unfortunately it's happened again today; anyone got any ideas? On both occasions the hub locked up when I was pedalling, not freewheeling; I can't see a mechanism for this as the freehub body and the hub are turning together in that situation. I don't really want to put more torque into the screw as the female thread is cut directly into the aluminium hub shell.

Thanks in advance

Des

keezx

Loctite looks the obvious solution to me.

desweller

Yeah mebbe. That's what I did last time and it didn't work. What would happen if I left that screw out? The freehub body on Shimano hubs is axially constrained by the wheel bearing cones...

keezx

The screw is the fixed connection between left and right bearings , so you can't leave it out.
Will not give you a ridable wheel.

crankycrank

I believe Shimano specs a 35-50Nm torque for the bolt so it can handle a good amount of force. Just wanting to be sure but are you positive all the splines on the freehub are lined up with the hub as well? It would probably be obvious if they weren't but you never know. Loctite shouldn't be necessary so I suspect something is damaged or installed incorrectly.

desweller

Interestingly, the manual for the 5800 hub (can't find one for the 5700) states that the hollow screw is not reuseable. You'd hope that a new one would be supplied with the freehub body if that was the case.

And as you say, the target torque is fairly high. I will definitely strip the thread in the hub if I go much higher. Maybe the hub's borked beyond repair already. I'm not sure what your point is about splines though, could you elaborate please?

If I can't come to a definite fix then I'm unlikely to risk it again; every time it happens the lock nuts mill a chunk out of the dropouts. I've spent 5 hours today repairing the frame, haven't got on to the wheel yet!

keezx

Once I had a loose screw on an old 105 hub, noticed it because the wheel wobbeled, but luckily it did not block the bearings, probably not torqued enough.
Once torqued sufficient It happened never again.
Seems no reason not to use the old screw again, looks solid steel.
Maybe the 5800 screw is alloy.
I would not take the risk of damaging the frame and get me a new hub.

desweller

The 5700 is definitely steel. I might - just - understand replacing it if the hub shell were steel, but I can't see it being placed under enough tensile load to plastically deform the threads running in an aluminium hub.

On the 5700 hub the freehub body is still constrained by the wheel bearings when the hollow screw is loose; I'm surprised that you had a wobbly body but perhaps the design is different.

Now that I've had more of a chance to think about it I feel the way I've repaired the frame might survive a few more bearing seizures as the clamping faces are now stainless steel rather than aluminiun. Or I could alter some old lock nuts I've got to reduce their grip on the frame until I'm confident my fix has worked. Still a couple of things to try...

Thanks everyone for your suggestions.

desweller

Well, having got round to the wheel itself (frame repairs are looking good!) I now understand why Shimano recommend replacing the hollow screw. It's the head of the screw that's the weak point; the contact land is very narrow and mine has actually fractured and come to pieces, releasing the tension on the screw.

New one on order!