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I have a Mavic Aksium Race rear wheel. The freehub was working and felt gunky.

I opened it to clean it (it was dry with some gunk and a bit of rust stains) and reassembled after lubricating with Finish Line's Dry Teflon Lube. Now the freehub turns freely both ways. And better than before cleaning.

I opened it again to remove any lubricant and cleaned again. Not luck.

I can clearly hear the pawls working well, but they won't ever engage, even when I turn it really slowly and wait for them to do so. I have also tried switching the pawls.

The side to side play around the nylon bushing is less than 0,5mm.

I have verified how I have reassembled it twice and have maintained such hubs dozens of times.

I don't have anything here to compare with, but if I was aksed if the pawls look worn, I would say yes.

My guess is that the pawls and freehub itself are worn out.

But the question is: how can a dirty worn working freehub can be cleaned and turned into a non-working clean worn freehub?

Thank you!

SuperBab
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    [Some interesting reading about services that particular free hub here : http://www.bikeforums.net/bicycle-mechanics/898554-overhaul-mavic-aksium-free-hub.html]

    A clutch wear and tear is visible to naked eye. Otherwise, you must get the exact model for the hub manual to check what is missing; some services part that open up may need replacement. You need to find the correct manual or youtube guide. sometime it can be very simple washer, bearing that make the clutch engagement.

     – mootmoot Jun 02 '16 at 17:27
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    Could you put some photos? Just for curiosity, I would try to fix this, if pawls are worn out like here: http://bicycles.stackexchange.com/questions/38802/shimano-nexus-3-sg-3c41-2-and-3-gear-problem-ring-gear-unit-repair/39287#39287 – krzyski Jun 02 '16 at 20:35
  • I'm having problems visualising this, but would it be possible to "sharpen" the catching edges of your pawls? I suspect that the gunk was providing a larger surface area for the pawls to catch on. Now you've cleaned it, there's less contact area so it slides before catching. I've done a vaguely similar fix by sharpening the handbrake pawl in my 25 year old car. – Criggie Jun 03 '16 at 02:47

2 Answers2

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Here is the explanation to what happened:

The freehub bearing had been moved outside for about 2,5mm. When reassembling the hub, the body wasn't sliding as far in the axle as it needed to. Thus, the pawls were not centered in the notches and not engaging.

But, I did replace the freehub body and pawls first, and they were engaging. However, when placing a great force, one pawl eventually gave up and broke at an angle.

Being able to see the angle of the fracture, I eventually deducted that the new pawls and freehub were engaging at an angle, so one end of the pawl was falling in the notch, while the other end was "higher", outside the notch.

I starting thinking about reasons for the pawls and notches not being aligned, which amounted to having the freehub not sliding far enough, and finally compared online pictures of the freehub bearing with what I have in hand. It was obvious that it was not pressed properly. After pressing in, the old freehub and pawls were installed and everything started working perfectly again, even the clicking sound got familiar again.

SuperBab
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  • Thank you for the closure, for telling how it went. I have but one upvote to give. Do also click the little "accept" tick/checkbox on the left side of the answer to make it the accepted answer. – Criggie Aug 05 '16 at 02:07
  • That was what I was about to guess as the problem, from reading the question :) Somehow I missed this one when it came through, sorry. Thanks for coming back and following up when you had an answer. – Móż Aug 05 '16 at 02:17
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Sometimes the term "rust was the only thing holding it together" has truth to it. Judging by the wheel and having done them before i assume you have A LOT of miles on the hubs.

If the pawls look visually worn they are probably not fully engaging the ratchet mechanism and under pressure with the help of their new lubricant, which has reduced the friction, they are slipping off the edge of the also worn ratchet.

I assume they have the "springy-ness" that they should? Their not sticking when depressed?

That's my guess, the dirt and micro grit may have been what was allowing them to still catch enough to engage. For a pawl to be visually worn means it's probably pretty bad as the tolerances for those internal parts is pretty tight.

Nate W
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  • Thanks for your input.

    Yes, they did have the springy-ness you would expect. To ensure this, I have just tested something: I have placed a very small square of tube rubber in the whole where the pawl's spring sit. The goal was to have pawls push harder against the notches. No luck, nothing works.

     – SuperBab Jun 02 '16 at 15:13
  • So do they just spin freely and never catch? And how well was it working before you cleaned it out? Was it slipping at all previously? – Nate W Jun 02 '16 at 15:27
  • They never catch. I can feel they are trying to, but not much.

    I am repairing this bicycle for someone else. That person never mentioned this issue when we checked the bike together.

    I haven't noticed anything when testing the bike on the stand, neither prior to disassembly.

     – SuperBab Jun 02 '16 at 15:29