Pinned rim - coming apart

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gbnz
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Joined: 13 Sep 2008, 10:38am

Pinned rim - coming apart

Post by gbnz »

Recently replaced the rear wheel with a heavy duty, sputnik rimmed wheel (Tired of lighter rear rims buckling/distorting, so finally went for a heavy duty wheel as a trouble free alternative).

Following 13 days on tour and 6 days on day rides (Road use)), the rim is now separating at the pinned join, with approximately half the join separated by a 0.5-0.75mm gap. I haven't any fear of it failing outright, however has anyone experience of such "separating rims" failing/pulling apart over time.

It's not an issue I've experienced previously, with a range of rigida (chrina), mavic, shimano, gippieme rims.
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531colin
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Re: Pinned rim - coming apart

Post by 531colin »

36 spokes at an average tension of 100 Kg (force) exert a compressive force on the rim which has the effect of keeping the rim joint closed. I have seen the force estimated, it was a lot!
If the rim is bent, the joint can become uneven.
Brucey
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Re: Pinned rim - coming apart

Post by Brucey »

^ WHS

If (say) your wheel is out of round near the rim joint and the rim joint appears to be opening, it will be the former causing the latter, not the other way round.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
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Mick F
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Re: Pinned rim - coming apart

Post by Mick F »

There's a long explanation somewhere on here by CJ discussing the forces involved holding the join together. Basically, in normal use with a normal wheel, the joint is impossible to pull apart.
Mick F. Cornwall
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cycleruk
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Re: Pinned rim - coming apart

Post by cycleruk »

With a loose joint isn't the rim likely to flex inwards at this point. :?:
Depending on circumstances I would be looking for a replacement.
You'll never know if you don't try it.
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CREPELLO
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Re: Pinned rim - coming apart

Post by CREPELLO »

Is the spoke tension tight and even?

I've corrected a rim where the joint slipped. I placed it between two blocks of wood and gave it a whack or 3. I might have used a support on one side of the join to make the unsupported side slide into position more easily.
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Mick F
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Re: Pinned rim - coming apart

Post by Mick F »

cycleruk wrote:With a loose joint isn't the rim likely to flex inwards at this point. :?:
If it bends inwards, it must bend outwards somewhere too.

If all the spokes were not tight enough, it could ovalise or cardio-ise.
If all the spokes were tight and the rim circular, any inward movement must be accompanied by an outward movement.
Mick F. Cornwall
gbnz
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Re: Pinned rim - coming apart

Post by gbnz »

CREPELLO wrote:Is the spoke tension tight and even?

I've corrected a rim where the joint slipped. I placed it between two blocks of wood and gave it a whack or 3. I might have used a support on one side of the join to make the unsupported side slide into position more easily.


Thanks to all.

My impression on receiving the hand built wheel, was that the spokes weren't as tight as I'd expect (They were noticeably looser than a wheel set from the same supplier, supplied four years earlier and any wheel I've built myself).

I'm not going to whack it, but may tighten everything by a margin (So much for saving the effort of building my own wheels :roll: )
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