Broken spoke heads - cause ?

Hi - machine built wheel on a low- to moderate end cyclocross bike :

Brand X hub (Joy-tech or something) laced with 14 g spokes
(32) to an assymetrical (Bontager) rim. I didn't expect
miracles on a $800 bike, but the wheel needed lots of truing
(essentially every ride) when new. Now about 1100 miles
(bike used for cross racing and training only, rarely sees
pavement but not abused). Fairly regularly (every 2-3
rides), a spoke head on the non-drive side will break at the
start of a ride (no other inpact other than my 185 lb ass
meeting the seat.) I've re-tensioned the wheels to match
(subjectively) my three sets of near-perfect road wheels -
I'm not hard on these and can go 1000's of miles withut
truing. My questions:

Is my non-drive side spoke tension too high or too low ? The
spokes don't seem too tense - have I miscalculated by
comparing the tension on this assymetrial eyelet rim to a
conventional rim ?

Is it something other than the spoke tension ? These are
also brand X spokes which I am replacing with DT as they go.

Thanks in advance for your thoughts ...........Lou D'Amelio

Quality of nipples varies considerably.
Also, if the spokes are too long or to short.
Too long and they can add stress to the nipples by forcing the nipple past the threaded portion of the spoke.
Take a look at the ends of the nipples. If there is more than 2 mm of the spoke protruding, the spokes are too long.
It spokes are to short and not engaging sufficient threads to act as a unit to handle the dynamic loading.

__________________
David Ornee, Western Springs, IL USA

If they were machine built, inexpensive wheels. it's
doubtful they were properly tentioned and stressed.
Take them to a reputable shop and have the wheels
properly tentioned, stressed and trued. This should
solve your problem

"May you have the wind at your back. And a really low gear
for the hills!"

Chris Zacho ~ "Your Friendly Neighborhood Wheelman"

Chris'Z Corner http://www.geocities.com/czcorner

"Lou D'Amelio" wrote:

> machine built wheel on a low- to moderate end
> cyclocross bike :
>
> Brand X hub (Joy-tech or something) laced with 14 g spokes
> (32) to an assymetrical (Bontager) rim. I didn't expect
> miracles on a $800 bike, but the wheel needed lots of
> truing (essentially every ride) when new. Now about 1100
> miles (bike used for cross racing and training only,
> rarely sees pavement but not abused). Fairly regularly
> (every 2-3 rides), a spoke head on the non-drive side will
> break at the start of a ride (no other inpact other than
> my 185 lb ass meeting the seat.)
>
> Is my non-drive side spoke tension too high or too low ?
> The spokes don't seem too tense - have I miscalculated by
> comparing the tension on this assymetrial eyelet rim to a
> conventional rim ?
>
> Is it something other than the spoke tension ? These
> are also brand X spokes which I am replacing with DT as
> they go.

Sounds like the wheel was badly built with bad spokes that
were also not stress relieved. I doubt that excess tension
is the problem. The fact that the wheel kept going out of
true indicates insufficient and/or uneven tension. The
failures are caused by fatigue.

Do the spoke heads seat firmly in the holes? Do the spokes
lay flat against the flange? The outbound spokes should have
been pressed against the flange when the wheel was being
built (before being fully tensioned).

I would ditch these spokes and rebuild with DT spokes
(assuming you still trust the hubs).

Art Harris

What was I thinking??????????
_____________________________________________

Ooops, I misread.
I agree with the other posters that the quality of the build is the likely issue.
Spoke alignment... see the illustrations and methods in "the Book"
Stress relieving..... see the illustration and method in "the Book"
Tension balancing.... tone by ear or with tension measuring device.
"the Book" = the Bicycle Wheel by Jobst Brandt
Quality spokes by DT, Sapim, or DT will serve you well.
I suggest that you use Double Butted spokes.

__________________
David Ornee, Western Springs, IL USA

Dear Lou,

It's odd that non-drive-side spokes are breaking
so often and so soon. This suggests that something
might be goofy about the relative tension of the
drive and non-drive sides.

But you might just have a batch of bad spokes,
either defective from the factory or somehow
damaged when the wheel was built.

If so, all the wheel-building tricks in the world
won't help--only replacement.

Can you make out a manufacturer's mark on
the remaining spoke heads? That is, what
brand are they?

Carl Fogel

ldamelio@patmedia.net (Lou D'Amelio) writes:

> Fairly regularly (every 2-3 rides), a spoke head on the
> non-drive side will break at the start of a ride (no other
> inpact other than my 185 lb ass meeting the seat.) I've
> re-tensioned the wheels to match (subjectively) my three
> sets of near-perfect road wheels - I'm not hard on these
> and can go 1000's of miles withut truing. My questions:
>
> Is my non-drive side spoke tension too high or too low ?
> The spokes don't seem too tense - have I miscalculated by
> comparing the tension on this assymetrial eyelet rim to a
> conventional rim ?

Make sure the wheel is built with the offset of the rim
towards the correct side. The spoke holes should be offset
away from the cassette.

> Is it something other than the spoke tension ? These
> are also brand X spokes which I am replacing with DT as
> they go.

Buy yourself a copy of _The Bicycle Wheel_ and read it. Then
follow the directions for properly tensioning and stress
relieving spokes. Have a few spare spokes on hand, because
if any are failing they process of stress relieving may
break them (which is good- better on the truing stand than
on a ride somewhere).

IMO when non-drive side spokes are breaking, the spoke
tension is too low and/or the spokes have not been stress
relieved. Although I did have a spate of failures with Asahi
spokes 6 or 8 years ago which none of these approaches
solved, and replacing them with DT or Wheelsmith (I can't
remember which now, and that wheel is gone) was necessary.
The Asahis were just crappy spokes.

these are fatigue failures. it happens and material quality
has a very significant effect on fatigue life. if you check,
i expect the spokes in the mtb wheels are a cheapo brand
compared to the road wheels - most spokes have an identifier
stamped into the head.

simply rebuild with decent quality spokes and they'll be
trouble free for a long long time.

Lou D'Amelio wrote:
> Hi - machine built wheel on a low- to moderate end
> cyclocross bike :
>
> Brand X hub (Joy-tech or something) laced with 14 g spokes
> (32) to an assymetrical (Bontager) rim. I didn't expect
> miracles on a $800 bike, but the wheel needed lots of
> truing (essentially every ride) when new. Now about 1100
> miles (bike used for cross racing and training only,
> rarely sees pavement but not abused). Fairly regularly
> (every 2-3 rides), a spoke head on the non-drive side will
> break at the start of a ride (no other inpact other than
> my 185 lb ass meeting the seat.) I've re-tensioned the
> wheels to match (subjectively) my three sets of near-
> perfect road wheels - I'm not hard on these and can go
> 1000's of miles withut truing. My questions:
>
> Is my non-drive side spoke tension too high or too low ?
> The spokes don't seem too tense - have I miscalculated by
> comparing the tension on this assymetrial eyelet rim to a
> conventional rim ?
>
> Is it something other than the spoke tension ? These
> are also brand X spokes which I am replacing with DT as
> they go.
>
> Thanks in advance for your thoughts ...........Lou
> D'Amelio

On 14 Mar 2004 05:47:22 -0800, ldamelio@patmedia.net (Lou D'Amelio)
wrote:

>Hi - machine built wheel on a low- to moderate end
>cyclocross bike :
>
>Brand X hub (Joy-tech or something) laced with 14 g spokes
>(32) to an assymetrical (Bontager) rim. I didn't expect
>miracles on a $800 bike, but the wheel needed lots of
>truing (essentially every ride) when new. Now about 1100
>miles (bike used for cross racing and training only, rarely
>sees pavement but not abused). Fairly regularly (every 2-3
>rides), a spoke head on the non-drive side will break at
>the start of a ride (no other inpact other than my 185 lb
>ass meeting the seat.) I've re-tensioned the wheels to
>match (subjectively) my three sets of near-perfect road
>wheels - I'm not hard on these and can go 1000's of miles
>withut truing. My questions:
>
>Is my non-drive side spoke tension too high or too low ?
>The spokes don't seem too tense - have I miscalculated by
>comparing the tension on this assymetrial eyelet rim to a
>conventional rim ?
>
>Is it something other than the spoke tension ? These
>are also brand X spokes which I am replacing with DT
>as they go.
>
>Thanks in advance for your thoughts ...........Lou D'Amelio

You've already gotten some good advice. Here are a few
related thoughts:

1. If you're the original owner, take the wheels back to
the dealer.

2. Measure the spoke elbow (Dimension E at Chun Nan's web
site: http://www.cnspoke.com/products/measure.htm).
Although it may have changed slightly during wheel
building, you should be able to make out whether they're
closer to 6.2~6.3 (as DT learned) or to 7.0mm (as no-name
spokes often are). See Peter Jon White's experience of
how this affects chances of spokes breaking:
http://www.peterwhitecycles.com/DTspokes.htm

3. Once you've got spokes with the smaller elbow, then
correct the spoke line, tension and stress relieve per
The Bicycle Wheel.

In article
<cc0f397f.0403140547.376e2dfc@posting.google.com>,
ldamelio@patmedia.net says...
>Hi - machine built wheel on a low- to moderate end
>cyclocross bike : Brand X hub (Joy-tech or something) laced
>with 14 g spokes (32) to an assymetrical (Bontager) rim. I
>didn't expect miracles on a $800 bike, but the wheel needed
>lots of truing (essentially every ride) when new. Now about
>1100 miles (bike used for cross racing and training only,
>rarely sees pavement but not abused). Fairly regularly
>(every 2-3 rides), a spoke head on the non-drive side will
>break at the start of a ride (no other inpact other than my
>185 lb ass meeting the seat.) I've re-tensioned the wheels
>to match (subjectively) my three sets of near-perfect road
>wheels - I'm not hard on these and can go 1000's of miles
>withut truing. My questions: Is my non-drive side spoke
>tension too high or too low ? The spokes don't seem too
>tense - have I miscalculated by comparing the tension on
>this assymetrial eyelet rim to a conventional rim ? Is it
>something other than the spoke tension ? These are also
>brand X spokes which I am replacing with DT as they go.

Probably under tensioned. That more than one spoke is
breaking on a regular basis means all the spokes will
eventually fail in the same way. Best bet is to get the
wheel rebuilt by someone who knows how to build good wheels.
You could also do it yourself. Get a copy of 'The Bicycle
Wheel' by Jobst Brandt and follow the directions.
---------------
Alex