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Accident post mortem.

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  • September 6, 2020 at 6:21 pm #31114
    don simon fbpe

    I managed to get spat off the bike last week and and looking for possible reasons. I’m not in a current state to look around the bike as the broken shoulder and muscle damage on right leg is somewhat restricting.

    Riding along at about 30km/h and the rear wheel locked up. this caused a slide which ultimately high sided and spat me off, I got back on and rode a further 1.5km. Nothing obviously broken on the bike. Rear mech intact, so not too sure if chain had jumped off the cassette. No potholes, no obstacles. It was an immediate and violent action from the bike (which makes me think that no stress was put on rear mech or hanger) and I’ll give it a good look over when more mobile. No one else was involved.

    Any thoughts of the cause in the meantime?

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  • November 20, 2020 at 9:19 am #970163
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    don simon fbpe

    Not too late at all. All

    Not too late at all. All possibilities welcome and good advice to check and double check th QRs before leaving home.

    November 20, 2020 at 7:08 am #970161
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    heppy

    Bit late, perhaps, but I had
    Bit late, perhaps, but I had something very similar cause by a loose rear skewer. I thought I’d tightened it enough but the resistance was due to friction in the (badly designed) cam, not clamping force. The wheel popped out soon after starting off out of the saddle, so I was spat (exactly that!) out over the bars. It was obvious what had happened looking at the wheel, but I reckon there’s a chance the axle end could have popped back into the drop-out, in which case there’d be no obvious clue

    November 19, 2020 at 10:22 pm #970159
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    TheBillder

    Thanks. I’ll go for it!
    Thanks. I’ll go for it!

    November 19, 2020 at 9:46 pm #970157
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    don simon fbpe

    That’s it, nothing else.

    That’s it, nothing else.

    https://cdn.road.cc/wp-content/uploads/roadcc/20201119_202447.jpg

    November 19, 2020 at 9:45 pm #970155
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    don simon fbpe

    Here’s the only damage I can

    Here’s the only damage I can find on the bike. Not much to show for coming off at 30-35km/h

    https://cdn.road.cc/wp-content/uploads/roadcc/20201119_202425.jpg

    November 19, 2020 at 9:38 pm #970153
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    don simon fbpe

    Quote:


    TheBillder replied to don simon fbpe | 370 posts | 7 min ago
    0 likes  

    Any tips on Fulcrum free hub servicing?

    My spare back wheel is a very lowly Racing Sport DB* with a clunky free hub. Last time it broke it spent 2 months in the shop waiting for new pawls. I keep meaning to strip it and see what’s up (possibly just mucky) but I hear worrying tales of springs making the pawls fly out, never to be retrieved from the wasp corpses in the corner of the shed…

    *the DB is true but not the Racing or the Sport.

     

    Fulcrum are a nightmare, in that I guess they use  different freehubs. Mine was sealed so I couldn’t attack the pawls.

    The Zonda, which is the same as some Fulcum (there’s a surprise) has removable freebub. The spring a) isn’t going anywhere as it should be hooked in and b) should probably be replaced (Ebay), so flying off isn’t a problem. Pawls and/or complete freehubs should be available there too.

    Measure the bearings an google the measurements to find cheaper bearings.

    Watch videos, and prepared to take 10x longer, hit bearings 10x harder and skin knuckles more than pro mechanic.

    Get a decent bearing press.

    If the wheel is spare and doing nothing, what’ve you got yo lose by having a look.

    I fear this is a bit of a tangent.

    November 19, 2020 at 9:35 pm #970151
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    don simon fbpe

    100% certain it’s not that.

    100% certain it’s not that. No broken spokes, no bent spokes and no scratches or marks on the dust dirt that’s accumulated on the spokes. No noise at the time of the accident. The only thing I’m currently more certain about is that this tory govt is corrupt.

    September 30, 2020 at 12:27 pm #970149
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    hawkinspeter

    That’s sounding like some
    That’s sounding like some road debris (branch?) got caught up in your wheel, then. Good luck with the riding.

    September 30, 2020 at 11:00 am #970147
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    don simon fbpe

    After stripping the freehub

    After stripping the freehub down and replacing the bearings, and no obvious faults in the wheel bearings, I now hopefully have a fully functioning rear wheel which will be put to the test on the rollers this evening.

    Here’s looking at another few 100 thousand kms before the next freak accident.

    September 10, 2020 at 5:49 pm #970145
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    don simon fbpe

    Absolutely no chance of that.

    Absolutely no chance of that.

    My money is on the hub.

    September 10, 2020 at 5:37 pm #970143
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    andystow

    What kind of brakes? Is it

    What kind of brakes? Is it possible the rear brake locked up hard?

    September 10, 2020 at 7:27 am #970141
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    don simon fbpe

    I wasn’t going particularly

    I wasn’t going particularly fast at the time, but another unexplained failure of a similar style sounds like the way forward. Again, I’m trying to get my head around the physical side of what happened, and why. It’ll be another week or so before I can get the bike on the stand. And a fair bit away from stripping the rear hub and there’s no local independent shops in town (walking distance) to get the wheel to.

    Muchas gracias! yes

     

    September 9, 2020 at 9:30 pm #970139
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    HoarseMann

    If you get the back wheel

    If you get the back wheel spinning up fast with the cranks on the stand, then stop the cranks you should see the chain droop if this is the problem. 

    It was a weird one to fault find as it wouldn’t happen when I was coasting at my usual pace, only when I’d got some speed up and stopped pedalling. Freehub still worked, but there was just that bit of drag that was enough to cause the chain to go slack.

    September 9, 2020 at 8:07 pm #970137
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    don simon fbpe

    Cheers, I’ll see if I can

    Cheers, I’ll see if I can have a play with it on the workstand when I get two fully functioning arms. Not sure I’ll be able to replicate that, but it might highlight something. yes

    September 9, 2020 at 7:22 pm #970135
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    HoarseMann

    I’ve had something similar

    I’ve had something similar with a failed freehub, but thankfully didn’t get spat off.

    It only started to happen when the speed picked up, the pawls were not allowing the freehub to spin when I eased off the power on the cranks (it didn’t completely not spin, but there was significant drag). This caused the upper part of the chain to go slack between the cassette and front mech. It felt a bit weird, I looked down and saw the chain slopped on the chain stay and dangerously close to the rear wheel spokes.

    It’s possible you had something similar, but were unlucky enough that the chain jammed the rear wheel. Hope you heal quickly.

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