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Bent rear hub axle - my fault?

Old 06-03-22, 10:36 AM
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JackJohn
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Bent rear hub axle - my fault?

Hi,
for the second bike in a row I found a bent rear hub axle: a Rossin with 6s FW on Campy hub, and a PX Peugeot with 5s FW on a Maillard Trophy hub. Unfortunately, although I tried the bikes after purchase, I didn’t properly check the hubs before removing the FW, and noticed the problem only after. In the first case the axle was significantly bent and needed to be replaced, in the second the bending was very limited and the FW wobbling barely visible, so I won’t change it.
I understand this was a quite common problem for old freewheels, especially with powerful riders or 6-7 speeds. But knowing I had to smash down hard the wrench on the FW remover over the standing bikes, I wonder whether I provoked that. Is it possible? Anyone experienced this before?
Many thanks.
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Old 06-03-22, 10:42 AM
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You are not likely to bend an axle when removing a freewheel - there should not be any load on the axle from this operation. The axle was much more likely to have been bent during riding.

Also, a bent axle does not cause freewheel wobble.
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Old 06-03-22, 10:44 AM
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Unless you're the original owner of the bikes and wheels, there's no way you can know what the wheels had to endure in the past. Also, I see plenty of discussion about how prone Campy axles can be to fracture, so I think you can be confident you didn't cause the issue. As far as what to do -- I see that folks tend to like Wheels Manufacturing replacement axles for Campy, but I don't know if the same holds true for Maillard. Others will weigh in, though.
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Old 06-03-22, 11:07 AM
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Originally Posted by ClydeClydeson
You are not likely to bend an axle when removing a freewheel - there should not be any load on the axle from this operation. The axle was much more likely to have been bent during riding.

Also, a bent axle does not cause freewheel wobble.
Thanks, ok for the wobble. Concerning the load, I thought pushing down strongly with a few powerful strokes was equivalent to the effect of the weight of a heavy rider.
Originally Posted by noobinsf
Unless you're the original owner of the bikes and wheels, there's no way you can know what the wheels had to endure in the past. Also, I see plenty of discussion about how prone Campy axles can be to fracture, so I think you can be confident you didn't cause the issue. As far as what to do -- I see that folks tend to like Wheels Manufacturing replacement axles for Campy, but I don't know if the same holds true for Maillard. Others will weigh in, though.
Thanks, indeed I don’t know the history of these bikes, so feel less guilty.
When I had to replace the Campy axle I found threading is different from standard, had checked on WM but then found one locally much cheaper.
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Old 06-03-22, 11:39 AM
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Originally Posted by JackJohn
Thanks, ok for the wobble. Concerning the load, I thought pushing down strongly with a few powerful strokes was equivalent to the effect of the weight of a heavy rider.
It is very possible that you could bend the axle by putting all your weight on it with some tool, but when using a freewheel removal tool, most of the load should be borne by the freewheel itself, and it should be primarily a turning force, not a bending force. I could be wrong, but FW axles are regularly bent by riding, and not regularly bent when removing freewheels.
Of course, most of my experience is in well equipped shops, and removing a freewheel with a FW remover clamped in a sturdy bench-mounted vice is less likely to put any bending force on the axle.
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Old 06-03-22, 12:03 PM
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6-speed FW hub axles are poorly supported on the right side because the right hub bearings are so far inboard. Famous for breaking or bending (the stye of failure mostly dependent on axle steel quality. Cheap ones bend, better endure more, then break.)

You can look at the axle like a classic sophomore engineering beam. Supported with rigid "fixed" supports at each end - the dropouts. Loaded with point loads at each bearing with your weight and whatever you are doing to the wheel. (Slamming potholes, jumping curbs ...) The fixed ends provided by the dropouts help a lot. But ... if those dropouts are not parallel, they are adding another issue - bending moment. Bending moment is what breaks axles. The loads on the bearings create bending moment. Adding more with the dropouts makes it worse.

So - before you put a new 6-speed FW axle on your bike, take it to a shop and have them put the dropout tools on. Two cylinders with handles that slide into the dropouts like a hub. If the dropouts are perfect the two cylinders line up, If not, the handles can be tweaked to bend the dropout into alignment. Every steel bike gets this or should. And after the bike falls over or crashes to the right. Or if shifting is off. Or axles are bending/breaking. Aluminum - bend with caution. One moderate bend is probably OK. Two, and it will break down the road. Carbon fiber? Out of my element. That might be a warranty issue.
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Old 06-03-22, 02:41 PM
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Originally Posted by ClydeClydeson
It is very possible that you could bend the axle by putting all your weight on it with some tool, but when using a freewheel removal tool, most of the load should be borne by the freewheel itself, and it should be primarily a turning force, not a bending force. I could be wrong, but FW axles are regularly bent by riding, and not regularly bent when removing freewheels.
Of course, most of my experience is in well equipped shops, and removing a freewheel with a FW remover clamped in a sturdy bench-mounted vice is less likely to put any bending force on the axle.
ok I see, very clear, the only thing I can think of is some excessive force on the chain whip when doing some tests… guess I’ll never know…
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Old 06-03-22, 02:42 PM
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Originally Posted by 79pmooney
6-speed FW hub axles are poorly supported on the right side because the right hub bearings are so far inboard. Famous for breaking or bending (the stye of failure mostly dependent on axle steel quality. Cheap ones bend, better endure more, then break.)

You can look at the axle like a classic sophomore engineering beam. Supported with rigid "fixed" supports at each end - the dropouts. Loaded with point loads at each bearing with your weight and whatever you are doing to the wheel. (Slamming potholes, jumping curbs ...) The fixed ends provided by the dropouts help a lot. But ... if those dropouts are not parallel, they are adding another issue - bending moment. Bending moment is what breaks axles. The loads on the bearings create bending moment. Adding more with the dropouts makes it worse.

So - before you put a new 6-speed FW axle on your bike, take it to a shop and have them put the dropout tools on. Two cylinders with handles that slide into the dropouts like a hub. If the dropouts are perfect the two cylinders line up, If not, the handles can be tweaked to bend the dropout into alignment. Every steel bike gets this or should. And after the bike falls over or crashes to the right. Or if shifting is off. Or axles are bending/breaking. Aluminum - bend with caution. One moderate bend is probably OK. Two, and it will break down the road. Carbon fiber? Out of my element. That might be a warranty issue.
thanks for the advice
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Old 06-03-22, 02:51 PM
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Originally Posted by JackJohn
ok I see, very clear, the only thing I can think of is some excessive force on the chain whip when doing some tests… guess I’ll never know…

Unless you had the chainwhip attached to the axle for some reason, then no, it would not bend the axle. The cogs and freewheel are not directly attached to the axle. For the same reason a bent axle will not cause freewheel wobble, applying a force to the cogs with a chainwhip will not bend the axle.

I am perplexed why you don't think it was bent by riding... did you put a new axle in and noticed it was bent before you rode it?
I've seen and fixed a lot of bent axles on freewheel equipped bikes but never imagined it was caused by anything other than riding, or maybe grossly misaligned dropouts (which would have been misaligned by a bent axle caused by riding).
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Old 06-03-22, 03:20 PM
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Originally Posted by JackJohn
ok I see, very clear, the only thing I can think of is some excessive force on the chain whip when doing some tests… guess I’ll never know…
Just curious -- what sort of "tests" were you doing with a chain whip on a freewheel mounted on the hub? What were you trying to accomplish?
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Old 06-03-22, 04:13 PM
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Originally Posted by ClydeClydeson
Unless you had the chainwhip attached to the axle for some reason, then no, it would not bend the axle. The cogs and freewheel are not directly attached to the axle. For the same reason a bent axle will not cause freewheel wobble, applying a force to the cogs with a chainwhip will not bend the axle.

I am perplexed why you don't think it was bent by riding... did you put a new axle in and noticed it was bent before you rode it?
I've seen and fixed a lot of bent axles on freewheel equipped bikes but never imagined it was caused by anything other than riding, or maybe grossly misaligned dropouts (which would have been misaligned by a bent axle caused by riding).
Yes it makes sense, bikes are quite old so previous owners riding and bending axles is very plausible… just wanted to clear my sense of guilt…
Originally Posted by JulesCW
Just curious -- what sort of "tests" were you doing with a chain whip on a freewheel mounted on the hub? What were you trying to accomplish?
I.e. servicing a Maillard FW and forcing to unscrew the first cogs, …
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Old 06-03-22, 04:38 PM
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If you could bend axles with just your upper body then you should be considering a career at the circus.
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Old 06-04-22, 12:43 PM
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Riding over One errant pothole can do it.
check the rim for dents or flat spots too.

very minor chance but worth the reference would be making sure the dropout faces are parallel- got to buy the tools or go to a knowledgeable local bike shop for that.
non parallel dropouts will not cause but with the wrong impact not help.
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Old 06-04-22, 01:21 PM
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Originally Posted by repechage
Riding over One errant pothole can do it.
check the rim for dents or flat spots too.

very minor chance but worth the reference would be making sure the dropout faces are parallel- got to buy the tools or go to a knowledgeable local bike shop for that.
non parallel dropouts will not cause but with the wrong impact not help.
Ok, note taken, thanks!
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Old 06-04-22, 02:03 PM
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You can make usable dropout alignment tools for a few bucks. Search YouTube.
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Old 06-04-22, 02:41 PM
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Originally Posted by smd4
You can make usable dropout alignment tools for a few bucks. Search YouTube.
yeah, will try…
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Old 06-04-22, 02:48 PM
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Originally Posted by smd4
You can make usable dropout alignment tools for a few bucks. Search YouTube.
not everyone is oriented for shade tree mechanical success
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Old 06-04-22, 02:53 PM
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Originally Posted by repechage
not everyone is oriented for shade tree mechanical success
Of course. Folks need to understand their skills and limitations. If he thinks he’s up to it, it’s not rocket science.
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