Rim failure

John Tomlinson

I have had rims fail on me before but not like this:

http://www.btinternet.com/~john.tomo/KIF_2154.JPG

Previously I have always worn through the side of the rim. This
failure, however, looks like the spokes are too tight - which is odd.

For about a year the wheel has been breaking spokes on a regular
basis; about one spoke every month or so and always on the none drive
side [1]. Until now I have blamed these breakages on the spokes being
too loose. But, I did not tighten the spokes, even though I wanted to
because the spoke nipples are at the end of their threads and cannot
be tightened any more. So how come the rim failed in this way with the
eyelet pulling out? Were the spokes too tight or too loose? I would
value to combined expertise of urc.

I should say that the eyelet has pulled out of a drive side spoke and
the wheel is on a Dawes Super Galaxy (new in 2000 - new to me in 2003)
so I would say the wheels are machine built.

Unless I can find a new rim and spokes tomorrow I shall be without a
bike over Christmas :-( I think Santa needs to bring me a second bike.

John T.


[1] - There are not many of the original non drive side spokes left.
Remove the singers of Spam before replying

motorhommer

Mileage ?

Type of wheel ?

dirtylitterboxofferingstospammers

>http://www.btinternet.com/~john.tomo/KIF_2154.JPG

Similar to what happened to an MA3 rim I used to have. On mine the cracking
extended along the inner surface of the rim

Cheers, helen s


--This is an invalid email address to avoid spam--
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Paul - xxx

John Tomlinson composed the following ...
> I have had rims fail on me before but not like this:
>
> http://www.btinternet.com/~john.tomo/KIF_2154.JPG
>
> Previously I have always worn through the side of the rim. This
> failure, however, looks like the spokes are too tight - which is odd.
>
> For about a year the wheel has been breaking spokes on a regular
> basis; about one spoke every month or so and always on the none drive
> side [1]. Until now I have blamed these breakages on the spokes being
> too loose. But, I did not tighten the spokes, even though I wanted to
> because the spoke nipples are at the end of their threads and cannot
> be tightened any more. So how come the rim failed in this way with the
> eyelet pulling out? Were the spokes too tight or too loose? I would
> value to combined expertise of urc.

Too loose spokes will tend to move in the sockets and Al rims don't take
kindly to brass nipples / eyelets being rubbed on them, no matter how small
the movements. This would normally lead to an elongation of the hole before
pulling through though ..

Your description above, though, suggests that the spokes may actually be the
wrong size for the hub / rim combination, or simply laced differently to how
the wheel was designed.

What does the inside of the rim look like, could there be any fluid in there
that has attacked the Al locally to this spoke and weakened it, something
like a drop of battery acid maybe ...


--
Paul ...
http://www.4x4prejudice.org/index.php
(8(!) Homer Rules ...
"A tosser is a tosser, no matter what mode of transport they're using."

Tony Raven

John Tomlinson wrote:
> I have had rims fail on me before but not like this:
>
> http://www.btinternet.com/~john.tomo/KIF_2154.JPG
>
> Previously I have always worn through the side of the rim. This
> failure, however, looks like the spokes are too tight - which is odd.
>
> For about a year the wheel has been breaking spokes on a regular
> basis; about one spoke every month or so and always on the none drive
> side [1]. Until now I have blamed these breakages on the spokes being
> too loose. But, I did not tighten the spokes, even though I wanted to
> because the spoke nipples are at the end of their threads and cannot
> be tightened any more. So how come the rim failed in this way with the
> eyelet pulling out? Were the spokes too tight or too loose? I would
> value to combined expertise of urc.
>
> I should say that the eyelet has pulled out of a drive side spoke and
> the wheel is on a Dawes Super Galaxy (new in 2000 - new to me in 2003)
> so I would say the wheels are machine built.
>
> Unless I can find a new rim and spokes tomorrow I shall be without a
> bike over Christmas :-( I think Santa needs to bring me a second bike.
>
> John T.
>
>
> [1] - There are not many of the original non drive side spokes left.
> Remove the singers of Spam before replying

Possibly too thick spokes and/or uneven tension between them due to
frequent replacements. The former results in less load sharing between
spokes and therefore more force on an individual eyelet and the latter
just exacerbates the problem. rec.bicycles.tech is the place to ask
although be prepared for the odd grouch in there. The following is in
their FAQ:

> - Choose spokes according to the type of wheel failure. If spoke or
> rim eyelet durability is a problem, use lighter spokes. It may seem
> odd to solve breaking problems by going to a lighter spoke; but
> spokes are run at 1/2 their yield strength or less, so do not break
> from overload. Instead, they fail from gradual degradation caused by
> repeated stretching and relaxing of the metal. Lighter spokes cause
> the wheel load to be shared among more spokes, reducing the loads on
> each spoke and thus improving spoke lifetime. A similar mechanism
> can damage rims at the eylet, and lighter spokes can therefore also
> help reduce rim damage. Note that using more spokes and a rim with
> greater radial stiffness also helps spoke and rim bed durability.


Tony

Pete Biggs

John Tomlinson wrote:
> I have had rims fail on me before but not like this:
>
> http://www.btinternet.com/~john.tomo/KIF_2154.JPG

You've got an extreme example but it's common to see some deformation and
cracking around eyelets. I last saw it on a Vuelta Tempest. I think it's
simply caused by excessive spoke tension for the rim.

Rims such as Open Pro, A719* (aka T520), X618 have sockets at the spoke
holes to distribute load more evenly between upper & lower walls to enable
the rim to take high tension, the kind of tension needed for strong rear
dished wheels. Too many rims (eg. MA3) don't have this feature.

* http://tinyurl.com/2xypb (diagram to bottom-right of pic is wrong and
illustrates another model with an alternative double-wall design without
sockets that's not as good IMO; these models tend to use weaker alloys as
well).

> Previously I have always worn through the side of the rim. This
> failure, however, looks like the spokes are too tight - which is odd.
>
> For about a year the wheel has been breaking spokes on a regular
> basis; about one spoke every month or so and always on the none drive
> side [1]. Until now I have blamed these breakages on the spokes being
> too loose.

Tight spokes can break too. Whatever, they probably weren't
stress-relieved.

> But, I did not tighten the spokes, even though I wanted to
> because the spoke nipples are at the end of their threads and cannot
> be tightened any more. So how come the rim failed in this way with the
> eyelet pulling out? Were the spokes too tight or too loose?

Maybe they were too tight (for the rim) in the first place.

> I should say that the eyelet has pulled out of a drive side spoke

That's where the highest trension is.

> and
> the wheel is on a Dawes Super Galaxy (new in 2000 - new to me in 2003)
> so I would say the wheels are machine built.

Machine built wheels don't have particularly high spoke tension but maybe
they were retensioned by hand.

However, I agree it's all a bit odd IF the left spokes were quite slack
(right spokes would then not be extremely tight if wheel is dished
correctly).

Anyway, wheels were never Dawes's strong point. T221 rims? Super Galaxy
deserves better. An A719 would be better for the rear at least, together
with some really good spokes, eg. DT Alpine III drive-side, DT Competition
or Sapim Laser left.

~PB

m-gineering

John Tomlinson wrote:
>
> I have had rims fail on me before but not like this:
>
> http://www.btinternet.com/~john.tomo/KIF_2154.JPG
>


you've been lucky, it is the 'prefered' mode of failure currently
--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

Just zis Guy, you know?

On Wed, 22 Dec 2004 22:46:06 +0000 (UTC), John Tomlinson
<john.tomo@pythonbtinternet.com> wrote in message
<5atjs0h907ffimrqcpnanp0tvrr7sbcb5c@4ax.com>:

>http://www.btinternet.com/~john.tomo/KIF_2154.JPG

Looks like uneven / insufficient tension. Almost certainly fatigue,
I'd say. What was the mileage?

Guy
--
"then came ye chavves, theyre cartes girded wyth candels
blue, and theyre beastes wyth straynge horn-lyke thyngs
onn theyre arses that theyre fartes be herde from myles
around." Chaucer, the Sheppey Tales

Pete Biggs

Just zis Guy, you know? wrote:

>> http://www.btinternet.com/~john.tomo/KIF_2154.JPG
>
> Looks like uneven / insufficient tension. Almost certainly fatigue,
> I'd say.

I would have thought too much tension, since it happened to John's on the
rear drive-side, and rims of mine after tightening spokes.

~PB

Just zis Guy, you know?

On Thu, 23 Dec 2004 12:04:31 -0000, "Pete Biggs"
<pwrinkledgrape{remove_fruit}@biggs.tc> wrote in message
<32vqfoF3ps1avU1@individual.net>:

>> Looks like uneven / insufficient tension. Almost certainly fatigue,
>> I'd say.

>I would have thought too much tension, since it happened to John's on the
>rear drive-side, and rims of mine after tightening spokes.

Maybe. I was thinking about the repeated load/unload cycles in the
bottom quadrant of the wheel as the it turns (note careful avoidance
of hang/stand argument), and considering that the rim may be less
likely to fail if the tension is maintained, than if it is dropped to
zero and re-applied repeatedly. But it's a guess. Fatigue is less of
a guess...

Guy
--
"then came ye chavves, theyre cartes girded wyth candels
blue, and theyre beastes wyth straynge horn-lyke thyngs
onn theyre arses that theyre fartes be herde from myles
around." Chaucer, the Sheppey Tales

Andy Dingley

On Wed, 22 Dec 2004 22:46:06 +0000 (UTC), John Tomlinson
<john.tomo@pythonbtinternet.com> wrote:

>I have had rims fail on me before but not like this:
>http://www.btinternet.com/~john.tomo/KIF_2154.JPG

What make of rim ?

I had a Mavic 217 go like this, long before reasonable wear should
have got to it. Popular opinion blamed Mavics and some cracking
problem related to their poor anodising. Under the microscope the tame
metallurgist reckoned there was considerable chemical corrosion,
although couldn't tell if this was cause or a resultant effect of
leaving cracks out in the rain.

One thing that did cross my mind was my bike cleaner. I use "Muc-Off",
which feels like it has a fair portion of potassium hydroxide in it,
which would certainly be a corrosion hazard on aluminium if it wasn't
washed off completely. Now I'm aware of this, so rinse carefully, but
around a nipple socket there's always going to be a trace left.

m-gineering

Andy Dingley wrote:
>
> On Wed, 22 Dec 2004 22:46:06 +0000 (UTC), John Tomlinson
> <john.tomo@pythonbtinternet.com> wrote:
>
> >I have had rims fail on me before but not like this:
> >http://www.btinternet.com/~john.tomo/KIF_2154.JPG

>
> One thing that did cross my mind was my bike cleaner.

I've had wheels returned before they got dirty! Single eyeletted FiRs
going in 200 km's. Some bikeparts are terrible, period
--
---
Marten Gerritsen

INFOapestaartjeM-GINEERINGpuntNL
www.m-gineering.nl

dkahn400

Andy Dingley wrote:

> metallurgist reckoned there was considerable chemical corrosion,
> although couldn't tell if this was cause or a resultant effect of
> leaving cracks out in the rain.

If you haven't got the space to bring your bike indoors, at least bring
in the cracks.

--
Dave...

Simon D

"m-gineering" <ikmotgeenspam@m-gineeringpunt.ennel.nl> wrote in message
news:41CADF3D.F53470AB@m-gineeringpunt.ennel.nl...
>
> I've had wheels returned before they got dirty! Single eyeletted FiRs
> going in 200 km's. Some bikeparts are terrible, period
> --
I agree entirely - rims are an example of cycle components having got
significantly poorer in quality over the past 20 years IMO.

As has been pointed out, fewer quality rims now have double eyelets, whilst
some manufacturers have tried to save too much weight (even on touring
rims). These factors have made them much more prone to the type of problem
experienced.

The wheel probably *wasn't* well tensioned from what you've said, but it's
likely that it was headed for an early grave regardless of how it was
assembled. There are some rims which are just not worth buying (Helen has
mentioned the MA3 for one...)