My Shimano freehub body stopped engaging during a ride on Saturday. No amount of shaking or banging would encourage it to turn the wheel with it when I pedalled.

Now when I come to take the cassette off, the hub is suddenly engaging again.

Should I regard the hub as likely to fail again at any moment? Would it be okay again after a service, or should I write it off?

NJM

It is only £17 for a new one. Is it worth the effort 😉

If you can get hold of something called ‘MEK’ (I think) and take the free hub mechanism off the hub (with a 10mm allen key I think), leave to soak over night. It should dissolve and degrease any sh1te on the ratchets, making it usable again. Failing some MEK, white spirit, petrol or some strong degreaser should do a similar job.

Also, whilst shimano freehubs aren’t supposed to be able to be dismantled, I have seen it done, although it was on an older Exage hub. And it also went back together fine.

shimano freewheels freeze up very easily, if it does it in cold weather then piss on it or use one of those small blowtorch/lighter things to thaw it out. once water gets in it will freeze in cold weather

“If you can get hold of something called ‘MEK’ (I think) and take the free hub mechanism off the hub (with a 10mm allen key I think), leave to soak over night. It should dissolve and degrease any sh1te on the ratchets, making it usable again.”

is it practical to get all the solvent out again and re grease the freehub? I’ve not seen an easy way to get fresh grease into a shimano freewheel?

http://morningstartools.com/freehub_buddy1.html

Leave the solvent to dry out (it will evaporate pretty quickly in air alone) and then get some decent lube like Finish Line XC to soak into the gap between the moving sections. Its a ratchet so I don’t think you necessarily need grease, just a good rust inhibitor/lubricant.

White spirit is oil based anyhow, not sure about MEK. Worth a shot to prolong the life of it, if it is knacked?

Andy, I’d agree though as per your first post, it may have been a frozen free hub rather than a clogged up one with the snowy weather especially.

MEK is methyl ethyl ketone, a volatile strong solvent. I’ll strip the grease alright but I’m not sure where you get it. Other volatile solvents may be just as good.

I’d try isopropyl alcohol or acetone maybe methanol as they should work and be easier to get hold of.

THey’re pretty aggressive chemicals so I wouldn’t use them unless you’re prepared to throw the freewheel away if it borks it.

Oh and read the MSDS the Lethal dose of methanol is surprisingly low it has irreversable effects in evne lower doses (makes you blind). Acetone is less dangerous and Isopropyl alcohol probably the safest it’s used in alcohol disinfectants. Do what ever you do in a well vented area wearing gloves.

Shimano freehubs can be taken apart – but don’t attempt near a fridge!