13g early spoke breakage

[v***@aol.com]

I've had a couple of major spoke failures on my main touring bike which
uses a sturmey Archer AG 36h Dynohub. On the last major failure,
luckily i was at the end of the street. I do around 150m per week, so i
started to think that heavier spokes would be a good idea. With that in
mind i got three wheels rebuilt using 13g generic steel x 36 , 14g DT's
x 40, and 13g Sapim single butted x 36 on a standard AW hub with
washers(all three stainless westrick rims). My plan was to test each
variant, by riding each till failure, in order to sort out the issue
once and for all. I figured that i would get atleast 3k miles out of
the 13g straight/g because the original 14g Raleigh factory spokes had
lasted since 1979 with some 300m per year. Anyway, 823 miles into the
first wheel, i hit first one, then another, small and invisible
potholes, whilst 25 miles out on a trip. Heard a loud snap and then
spent 25 very nervous miles limping home. Hopefully wheel two and three
will fair better.
I had a look at the spoke and the fracture surface is almost like
glass, with no signs of trauma or the usual rough fatigue pattern. This
put me in mind of an overly hardened endmill or some such that has
broken through being too brittle. Do these spokes sometimes get over
hardened or perhaps would a slightly softer spoke withstand impact
shocks without failing. Lastly, the Sapim Strong equipped wheel has
been built 4 cross by one of the UK's best wheelbuilders. Unfortunately
he couldn't find any 13g brass washers, so used standard, but slightly
larger nickle plated ones. Looking at the wheel, the spokes are curved
as they are forced to touch the adjacent spoke head upon exit of the
hub and some the washer edges, due to the accuteness of the 4x spoke
angle. Am i right to be worried that this contact will at some time
possibly damage and break the spoke heads? Is there any other way of
making the wheel bullet proof, or will one or two small pot holes
always destroy a wheel?
sorry for the long ramble.
cheers, Nick. England.

[Paul Kopit]

Post by v***@aol.com
I've had a couple of major spoke failures on my main touring bike which
uses a sturmey Archer AG 36h Dynohub. On the last major failure,
luckily i was at the end of the street. I do around 150m per week, so i
started to think that heavier spokes would be a good idea. With that in
mind i got three wheels rebuilt using 13g generic steel x 36 , 14g DT's
x 40, and 13g Sapim single butted x 36 on a standard AW hub with
washers(all three stainless westrick rims).

If the hub flanges are too wide for the dropout spacing, the builder
cannot get adequate tension on the non drive side. A hub built for
135 mm spacing that is respaced sometimes has this problem. I've had
this problem on the former Real Design road hubs. Respacing of your
hub to 135 mm if it is spaced narrower can help in this instance.

In my limited experience building tandem wheels, the 13 ga. spoke
haven't been as durable as 14/15ga butted spokes. Bead seats that are
wide enought to accept 700x35 tires. I've build the wheels to high
tension. The wheels I've built that have carried 400 lb. loads
haven't failed in 36 or 40 spoke wheels. Although I've built 4x I
don't believe that 3x would matter.

I'm not a professional builder and it takes me a long amount of time
to build a wheel. Others on this list are pros and can do better than
I can.

[steve]

Post by v***@aol.com
I've had a couple of major spoke failures on my main touring bike which
uses a sturmey Archer AG 36h Dynohub. On the last major failure,
luckily i was at the end of the street. I do around 150m per week, so i
started to think that heavier spokes would be a good idea. With that in
mind i got three wheels rebuilt using 13g generic steel x 36 , 14g DT's
x 40, and 13g Sapim single butted x 36 on a standard AW hub with
washers(all three stainless westrick rims). My plan was to test each
variant, by riding each till failure, in order to sort out the issue
once and for all. I figured that i would get atleast 3k miles out of
the 13g straight/g because the original 14g Raleigh factory spokes had
lasted since 1979 with some 300m per year. Anyway, 823 miles into the
first wheel, i hit first one, then another, small and invisible
potholes, whilst 25 miles out on a trip. Heard a loud snap and then
spent 25 very nervous miles limping home. Hopefully wheel two and three
will fair better.
I had a look at the spoke and the fracture surface is almost like
glass, with no signs of trauma or the usual rough fatigue pattern. This
put me in mind of an overly hardened endmill or some such that has
broken through being too brittle. Do these spokes sometimes get over
hardened or perhaps would a slightly softer spoke withstand impact
shocks without failing. Lastly, the Sapim Strong equipped wheel has
been built 4 cross by one of the UK's best wheelbuilders. Unfortunately
he couldn't find any 13g brass washers, so used standard, but slightly
larger nickle plated ones. Looking at the wheel, the spokes are curved
as they are forced to touch the adjacent spoke head upon exit of the
hub and some the washer edges, due to the accuteness of the 4x spoke
angle. Am i right to be worried that this contact will at some time
possibly damage and break the spoke heads? Is there any other way of
making the wheel bullet proof, or will one or two small pot holes
always destroy a wheel?
sorry for the long ramble.
cheers, Nick. England.

I would probably attribute your broken spokes to the fact that they are
generic spokes which are much more likely to use inferior steel that
can not handle cyclic loads well and there for will fatigue faster.
It is highly unlikely that your spokes broke as a result of a sudden
impact. Most likely the spokes had fatigued to a point that they
couldn't withstand the forces being exerted on the wheel and so they
broke. A spoke that has broken from fatigue will look very similiar to
a broken endmill. Another thing to keep in mind is that 13g is a thick
spoke that needs very little stretch to reach tensions used in a wheel.
There for it will take very little compression of the rim to completly
loose tension in that spoke which will accelerate your fatigue
dramaticly. As for the wheel with the Sapim strong spokes, it is
generally better to avoid having the spokes cross over the heads of the
adjacent spoke. While I have seen lots of wheels last for years laced
this way, I think the less bend you can induce on the spoke from the
hub to the rim, the lower stress the spoke will experience thus
allowing it to last longer. If nothing else, the type of lacing your
wheel has will make it more difficult to change spokes. Personally I
would lace that wheel with a three cross pattern to eliminate the bend
over the adjacent spoke. The only advantage that I am convinced 4x has
over 3x is that it is better at taking tortional loads.
If you are looking for a bomb proof wheel in terms of spoke life I
would look into wheels with higher spoke counts such as you 40 spoke
wheel and use thinner butted spokes like a 2.0/1.8. This will allow
your spokes to stretch more before they reach the optimal tension for
your wheel, there for making it much more unlikely that they will loose
there tension as the wheel rotates.

[Michael Press]

In article
<***@m58g2000cwm.googlegroups.com>
,

Post by steve

Post by v***@aol.com
I've had a couple of major spoke failures on my main touring bike which
uses a sturmey Archer AG 36h Dynohub. On the last major failure,
luckily i was at the end of the street. I do around 150m per week, so i
started to think that heavier spokes would be a good idea. With that in
mind i got three wheels rebuilt using 13g generic steel x 36 , 14g DT's
x 40, and 13g Sapim single butted x 36 on a standard AW hub with
washers(all three stainless westrick rims). My plan was to test each
variant, by riding each till failure, in order to sort out the issue
once and for all. I figured that i would get atleast 3k miles out of
the 13g straight/g because the original 14g Raleigh factory spokes had
lasted since 1979 with some 300m per year. Anyway, 823 miles into the
first wheel, i hit first one, then another, small and invisible
potholes, whilst 25 miles out on a trip. Heard a loud snap and then
spent 25 very nervous miles limping home. Hopefully wheel two and three
will fair better.
I had a look at the spoke and the fracture surface is almost like
glass, with no signs of trauma or the usual rough fatigue pattern. This
put me in mind of an overly hardened endmill or some such that has
broken through being too brittle. Do these spokes sometimes get over
hardened or perhaps would a slightly softer spoke withstand impact
shocks without failing. Lastly, the Sapim Strong equipped wheel has
been built 4 cross by one of the UK's best wheelbuilders. Unfortunately
he couldn't find any 13g brass washers, so used standard, but slightly
larger nickle plated ones. Looking at the wheel, the spokes are curved
as they are forced to touch the adjacent spoke head upon exit of the
hub and some the washer edges, due to the accuteness of the 4x spoke
angle. Am i right to be worried that this contact will at some time
possibly damage and break the spoke heads? Is there any other way of
making the wheel bullet proof, or will one or two small pot holes
always destroy a wheel?
sorry for the long ramble.
cheers, Nick. England.

I would probably attribute your broken spokes to the fact that they are
generic spokes which are much more likely to use inferior steel that
can not handle cyclic loads well and there for will fatigue faster.
It is highly unlikely that your spokes broke as a result of a sudden
impact. Most likely the spokes had fatigued to a point that they
couldn't withstand the forces being exerted on the wheel and so they
broke. A spoke that has broken from fatigue will look very similiar to
a broken endmill. Another thing to keep in mind is that 13g is a thick
spoke that needs very little stretch to reach tensions used in a wheel.
There for it will take very little compression of the rim to completly
loose tension in that spoke which will accelerate your fatigue
dramaticly. As for the wheel with the Sapim strong spokes, it is
generally better to avoid having the spokes cross over the heads of the
adjacent spoke. While I have seen lots of wheels last for years laced
this way, I think the less bend you can induce on the spoke from the
hub to the rim, the lower stress the spoke will experience thus
allowing it to last longer. If nothing else, the type of lacing your
wheel has will make it more difficult to change spokes. Personally I
would lace that wheel with a three cross pattern to eliminate the bend
over the adjacent spoke. The only advantage that I am convinced 4x has
over 3x is that it is better at taking tortional loads.
If you are looking for a bomb proof wheel in terms of spoke life I
would look into wheels with higher spoke counts such as you 40 spoke
wheel and use thinner butted spokes like a 2.0/1.8. This will allow
your spokes to stretch more before they reach the optimal tension for
your wheel, there for making it much more unlikely that they will loose
there tension as the wheel rotates.

Nick, steve says it all.

[v***@aol.com]

Many thanks for all the replies, it's much appreciated. I'll have to
see if i can find a good 40 hole Sturmey and get it laced with the
suggested spokes with washers and see how many miles it will do. I
really had thought that any spoke would last a couple of thousand,
regardless of installation. Saying that, the lad which i used on the
first two wheels is a bit of a novice. He ground away half the head of
each nipple, so he probably didn't have the correct length spokes to
begin with. Just one question, if 13g straight gauge spokes are prone
to low tension fatigue, do they suffer from the same problem on
motorcycle wheels such as Harleys. Anyone know what the situation is
with motorbikes. When i use to mess around with them, i don't think
that i ever came across a broken spoke. Anyway thanks again for the
replies, i'll try to apply some of the advice and record the results.
cheers, Nick.

[c***@comcast.net]

Post by v***@aol.com
Many thanks for all the replies, it's much appreciated. I'll have to
see if i can find a good 40 hole Sturmey and get it laced with the
suggested spokes with washers and see how many miles it will do. I
really had thought that any spoke would last a couple of thousand,
regardless of installation. Saying that, the lad which i used on the
first two wheels is a bit of a novice. He ground away half the head of
each nipple, so he probably didn't have the correct length spokes to
begin with. Just one question, if 13g straight gauge spokes are prone
to low tension fatigue, do they suffer from the same problem on
motorcycle wheels such as Harleys. Anyone know what the situation is
with motorbikes. When i use to mess around with them, i don't think
that i ever came across a broken spoke. Anyway thanks again for the
replies, i'll try to apply some of the advice and record the results.
cheers, Nick.

Dear V,

The spoke debates on RBT tend to mystify motorcycle mechanics.

One theory is that motorcycle rims and spokes are so much stouter that
bicycle spoke problems are eliminated. Here's a husky straight 2 mm
bicycle spoke next to its single-butted 4.0 x 3.5 mm big brother from
a delicate trials machine:

Loading Image...

Another theory is that bicyclists may be fooling themselves with some
of their more elaborate explanations.

I happily subscribe to both theories, depending on the day of the
week.

Cheers,

Carl Fogel

[v***@aol.com]

that's the funny thing, if it was just as simple as , thick spoke=low
tension=more fatigue effects, then Motorbikes would be spread out all
along the M1. Maybe 3.5mm is above a threshold where a wheel rotation
cycle doesn't produce the kind of stresses encountered on my poor long
suffering Raleighs. I think losing 2 stone will be the start of
solving this particular problem. Fascinating that you say MC mechanics
are baffled by this, if i had time i would design a study to sort this
question out. Are there any tandem users out there that can offer any
experience with 13g spokes versus double butted 14/12g DT Swiss's or
the like?

Post by c***@comcast.net

Post by v***@aol.com
Many thanks for all the replies, it's much appreciated. I'll have to
see if i can find a good 40 hole Sturmey and get it laced with the
suggested spokes with washers and see how many miles it will do. I
really had thought that any spoke would last a couple of thousand,
regardless of installation. Saying that, the lad which i used on the
first two wheels is a bit of a novice. He ground away half the head of
each nipple, so he probably didn't have the correct length spokes to
begin with. Just one question, if 13g straight gauge spokes are prone
to low tension fatigue, do they suffer from the same problem on
motorcycle wheels such as Harleys. Anyone know what the situation is
with motorbikes. When i use to mess around with them, i don't think
that i ever came across a broken spoke. Anyway thanks again for the
replies, i'll try to apply some of the advice and record the results.
cheers, Nick.Dear V,

The spoke debates on RBT tend to mystify motorcycle mechanics.
One theory is that motorcycle rims and spokes are so much stouter that
bicycle spoke problems are eliminated. Here's a husky straight 2 mm
bicycle spoke next to its single-butted 4.0 x 3.5 mm big brother from
http://home.comcast.net/~carlfogel/download/spokes.jpg
Another theory is that bicyclists may be fooling themselves with some
of their more elaborate explanations.
I happily subscribe to both theories, depending on the day of the
week.
Cheers,
Carl Fogel

[peter]

Post by v***@aol.com
Are there any tandem users out there that can offer any
experience with 13g spokes versus double butted 14/12g DT Swiss's or
the like?

We had a similar experience with our tandem about 30 years ago. The
original (14g?) spokes had lasted a reasonable amount of time in the
very large flange (drum brake) 36 hole wheel, but eventually they
started breaking with some regularity. The replacement 14g spokes
only lasted about 1000 miles so I thought I'd try using even heavier
gauge spokes. The 13g ones were even worse and only lasted about 600
miles. We finally gave up on that wheel and switched to a 48-hole
normal flange hub with 14/15 butted DT spokes. Those spokes are still
on the bike today.

[j***@stanfordalumni.org]

Post by peter

Are there any tandem users out there that can offer any experience
with 13g spokes versus double butted 14/12g DT Swiss or the like?

We had a similar experience with our tandem about 30 years ago. The
original (14g?) spokes had lasted a reasonable amount of time in the
very large flange (drum brake) 36 hole wheel, but eventually they
started breaking with some regularity. The replacement 14g spokes
only lasted about 1000 miles so I thought I'd try using even heavier
gauge spokes. The 13g ones were even worse and only lasted about
600 miles. We finally gave up on that wheel and switched to a
48-hole normal flange hub with 14/15 butted DT spokes. Those spokes
are still on the bike today.

I think this doesn't conclusively connect cause and effect.
Motorcycle rims are far more rigid in all directions than bicycle
rims, the most important mode being radial.

I believe your experience showed that the stiffer the spoke on your
tandem, the more concentrated the load on the spoke pointing straight
down was and in this, the thicker spoke is more highly stressed
because only one or two spokes is taking the load. The motorcycle rim
distributes load to a whole section of spokes in spite of their
stiffness and these are stronger than bicycle spokes, so fatiguing
stress is not reached readily.

Jobst Brandt

[peter]

Post by j***@stanfordalumni.org

Post by peter

Are there any tandem users out there that can offer any experience
with 13g spokes versus double butted 14/12g DT Swiss or the like?

We had a similar experience with our tandem about 30 years ago. The
original (14g?) spokes had lasted a reasonable amount of time in the
very large flange (drum brake) 36 hole wheel, but eventually they
started breaking with some regularity. The replacement 14g spokes
only lasted about 1000 miles so I thought I'd try using even heavier
gauge spokes. The 13g ones were even worse and only lasted about
600 miles. We finally gave up on that wheel and switched to a
48-hole normal flange hub with 14/15 butted DT spokes. Those spokes
are still on the bike today.

I think this doesn't conclusively connect cause and effect.
Motorcycle rims are far more rigid in all directions than bicycle
rims, the most important mode being radial.

Obviously, and I don't see anything in my statement above that
indicates anything to the contrary.
You seem to once again be reading things into posts that aren't
actually there.

[j***@stanfordalumni.org]

Post by peter

Post by j***@stanfordalumni.org

Post by peter

Post by v***@aol.com
Are there any tandem users out there that can offer any
experience with 13g spokes versus double butted 14/12g DT Swiss
or the like?

We had a similar experience with our tandem about 30 years ago.
The original (14g?) spokes had lasted a reasonable amount of time
in the very large flange (drum brake) 36 hole wheel, but
eventually they started breaking with some regularity. The
replacement 14g spokes only lasted about 1000 miles so I thought
I'd try using even heavier gauge spokes. The 13g ones were even
worse and only lasted about 600 miles. We finally gave up on that
wheel and switched to a 48-hole normal flange hub with 14/15
butted DT spokes. Those spokes are still on the bike today.

I think this doesn't conclusively connect cause and effect.
Motorcycle rims are far more rigid in all directions than bicycle
rims, the most important mode being radial.

Obviously, and I don't see anything in my statement above that
indicates anything to the contrary. You seem to once again be
reading things into posts that aren't actually there.

Well then there wasn't any reason to recall the experience if there is
no cause and effect relationship between what you did and spoke
breakage, the subject of this thread. I admit the linkage is not
clearly expressed about what caused what, but it is resonable to look
for one in light of the OP's question.

Jobst Brandt

[v***@aol.com]

thanks for the info Jobst and Carl. My rim is a Stainless steel 26 x
1 3/8 Vanschothorst Westrick rim, which as far as i can tell from my
limited knowledge is strong as an ox. I am coming to the conclusion
that the lad in the bike shop is almost certainly not experienced in
the finer Guru points of proper tension and stress relief. In fact the
replacement wheel that i'm now using(also built by him), was so full
of almost loose spokes, that i had to take it to a proper wheelbuilder
in Market Harborough near to where i live so that he could work his
skill on it. He laughed when he looked at it and said that it was a
right mess. Maybe it is just a case of finding a good UK wheelbuilder
or buy Musson's/Jobst's book and start wheelbuilding. Thanks kindly
for all your help.
I was thinking, while nervously riding back the 25 miles
with the broken spoke, that the thicker the wire section, the more
energy is directed at the spoke bend. Has anyone ever developed a 'C'
coupling or circular unit composed of multiple 'C' couplings which
would obviate the need for spoke bends and allow you to bolt on the
required number of coupling so that a spoke could screw straight into
the coupling and then the coupling could be bolted throught the
flange. Or is it a case that you still need to turn 90 deg, so the
fatique process will still apply to the 'C' coupling intersections? I
would of though that a two piece casting could be produced to convert
existing hubs to straight spokes without a bend. Has this ever been
tried? I know that its not cost effective and its better to start from
scratch. Maybe one day the people at sturmey archer or someone else
will design and build a straight spoked 40 hole AW shell, now that
would be interesting to test.
cheers, Nick.

Post by j***@stanfordalumni.org

Are there any tandem users out there that can offer any experience
with 13g spokes versus double butted 14/12g DT Swiss or the like?

We had a similar experience with our tandem about 30 years ago. �The
original (14g?) spokes had lasted a reasonable amount of time in the
very large flange (drum brake) 36 hole wheel, but eventually they
started breaking with some regularity. �The replacement 14g spokes
only lasted about 1000 miles so I thought I'd try using even heavier
gauge spokes. �The 13g ones were even worse and only lasted about
600 miles. �We finally gave up on that wheel and switched to a
48-hole normal flange hub with 14/15 butted DT spokes. �Those spokes
are still on the bike today.I think this doesn't conclusively connect cause and effect.

Motorcycle rims are far more rigid in all directions than bicycle
rims, the most important mode being radial.
I believe your experience showed that the stiffer the spoke on your
tandem, the more concentrated the load on the spoke pointing straight
down was and in this, the thicker spoke is more highly stressed
because only one or two spokes is taking the load. �The motorcycle rim
distributes load to a whole section of spokes in spite of their
stiffness and these are stronger than bicycle spokes, so fatiguing
stress is not reached readily.
Jobst Brandt

[c***@comcast.net]

On 29 Jan 2007 03:21:15 -0800, ***@aol.com wrote:

[snip]

Post by v***@aol.com
Maybe it is just a case of finding a good UK wheelbuilder
or buy Musson's/Jobst's book and start wheelbuilding.

[snip]

Dear V,

Interesting! I hadn't heard of Roger Musson's ebook about building
bicycle wheels, now in its third edition since 1996 and updated this
month:

http://www.wheelpro.co.uk/wheelbuilding/book.php

He also has an online spoke-length calculator, with some explanations
and suggestions about measuring things:

http://www.wheelpro.co.uk/spokecalc

Cheers,

Carl Fogel

[Ted Bennett]

Post by v***@aol.com
thanks for the info Jobst and Carl. My rim is a Stainless steel 26 x
1 3/8 Vanschothorst Westrick rim, which as far as i can tell from my
limited knowledge is strong as an ox.

Are you certain the rim is of stainless steel, rather than alumin(i)um?
Never having seen a stainless rim, I am intrigued.

[c***@comcast.net]

On Mon, 29 Jan 2007 19:54:00 GMT, Ted Bennett

Post by Ted Bennett

Post by v***@aol.com
thanks for the info Jobst and Carl. My rim is a Stainless steel 26 x
1 3/8 Vanschothorst Westrick rim, which as far as i can tell from my
limited knowledge is strong as an ox.

Are you certain the rim is of stainless steel, rather than alumin(i)um?
Never having seen a stainless rim, I am intrigued.

Dear Ted,

Van Schothorst makes a variety of stainless steel rims. Here's one:

http://www.sjscycles.co.uk/sessionID/CND/product-36h-Van-Schothorst-Saphir-700c-Stainless-Steel-(18-10)-rim-4945.htm

or http://tinyurl.com/39wj89

Cheers,

Carl Fogel

[v***@aol.com]

as Carl says they make a good range of traditional and regular 700c
rims. My Stainless rims are double skinned and obviously never rust or
wear as do the modern alloy rims( just a conspiracy by the makers to
get you to buy more rims, ha). It's a shame that they only do upto 36
spoke versions, though i saw a 40 hole on Ebay a few days back.
Eventually i'll find a stainless 40 and match it to a 40 hole Sturmey
hub and then ride it to destruction to find out how many miles such a
wheel can give. I weighed the Raleigh today and it came in at 54lb
loaded with fishing gear 39lb without. Looks like a rear wheel load of
about 200lbs, which obviously is going to kill any wheel sooner or
later.

I meant to ask, does innertube pressure lower spoke tension via
contracting the rim?
all the best, Nick.

[c***@comcast.net]

Post by v***@aol.com
as Carl says they make a good range of traditional and regular 700c
rims. My Stainless rims are double skinned and obviously never rust or
wear as do the modern alloy rims( just a conspiracy by the makers to
get you to buy more rims, ha). It's a shame that they only do upto 36
spoke versions, though i saw a 40 hole on Ebay a few days back.
Eventually i'll find a stainless 40 and match it to a 40 hole Sturmey
hub and then ride it to destruction to find out how many miles such a
wheel can give. I weighed the Raleigh today and it came in at 54lb
loaded with fishing gear 39lb without. Looks like a rear wheel load of
about 200lbs, which obviously is going to kill any wheel sooner or
later.
I meant to ask, does innertube pressure lower spoke tension via
contracting the rim?
all the best, Nick.

Dear Nick,

It turns out that the answer is yes and no, inflation can raise or
lower spoke tension.

In stiff, narrow 700c rims, inflating a tire chokes the rim, squeezing
it like a python, and lowering the spoke tension.

The culprit is the angle of the tire plies. As the tire expands, the
angle of its plies can cause it to shorten, much like a Chinese
finger-trap toy. As the tire shortens, it constricts, squeezing the
rim and taking some of the tension previously supplied by the spokes.

Here's a nice page showing how this can be demonstrated with a spoke
tension gauge:

http://www.geocities.com/dianne_1234/bikes/tension-inflation/tension-inflation.htm

As Dianne's pictures show, the spoke tension gauge needle rose as the
tire deflated, showing that the inflated tire had squeezed the rim and
lowered the spoke tension.

But things aren't always as simple as they ought to be. I happened to
think of Dianne's demonstration one day because I had my spoke tension
gauge out and a helpless MTB wheel and tire handy. It seemed like a
harmless way to amuse myself--hang the spoke tension gauge on a spoke,
let the air out of the tire, and watch the needle rise.

Instead, the damned needle dropped.

http://groups.google.com/group/rec.bicycles.tech/browse_frm/thread/e3864af31619d8d4/511343ee76d906fd?lnk=gst&q=dianne+inflation+700c+carl&rnum=1#511343ee76d906fd
or http://tinyurl.com/2jpnhq

To make a long story short, the inflated tire was probably still
trying to constrict, squeeze the rim into a smaller circle, and lower
the spoke tension.

But at the same time, the fat MTB tire was also spreading the broad
rim flanges even further apart. When the broad vee of the rim spread,
the center of the rim was pulled outward, increasing spoke tension.

Mike Schwab suggested this explanation and asked how far the rim
spread. Measurements showed that at 60 psi the simple no-box MTB rim
spread outward 6 times as much as a simple no-box 700c rim at 120 psi,
and 36 times as much as a box-section 700c rim.

So there are actually two forces at work when a tire is inflated.

The tire shortens around the rim, constricting and squeezing it into a
smaller circle, lowering the original spoke tension. Pump the tire up,
and this effect will lower spoke tension.

But the tire also tries to spread the rim sideways, which pulls the
central line around the rim away from the hub, increasing spoke
tension. In narrow, well-braced 700c rims, this spreading effect is
tiny and overwhelmed by the tire constriction. In broad, poorly braced
MTB rims, the spreading effect can overwhelm the tire constriction and
make a tension gauge needle move the "wrong" way in a startling
fashion.

Cheers,

Carl Fogel

[A Muzi]

Post by Ted Bennett

Post by v***@aol.com
thanks for the info Jobst and Carl. My rim is a Stainless steel 26 x
1 3/8 Vanschothorst Westrick rim, which as far as i can tell from my
limited knowledge is strong as an ox.

Are you certain the rim is of stainless steel, rather than alumin(i)um?
Never having seen a stainless rim, I am intrigued.

Mid-to-expensive European 'city' bikes , especially Dutch ones, have/had
stainless rims.

Yes, aluminum gives _much_ better braking! But in 28 x 1-1/2 -635 for
example stainless is available and aluminum is not. In his size and
Westrick section, stainless is preferred by consumers. I don't think
such an aluminum rim exists (?)

[b***@mambo.ucolick.org]

... Just one question, if 13g straight gauge spokes are prone
to low tension fatigue, do they suffer from the same problem on
motorcycle wheels such as Harleys. Anyone know what the situation is
with motorbikes. When i use to mess around with them, i don't think
that i ever came across a broken spoke. Anyway thanks again for the
replies, i'll try to apply some of the advice and record the results.

Bicycle wheel rims are quite light and are generally the
limiting factor on how much tension you can safely put
on the spokes. Motorcycle rims are a lot stiffer and more
resistant to pull through so you could use fatter spokes
and high tension.

In some sense the spokes should match the rims; building
a wheel with a light rim and heavy spokes is not guaranteed
to make a stronger structure than a light rim and light spokes.
The seemingly paradoxical thing is that it's the heavy spokes
that can break. Although this isn't really a paradox because
we are talking about cyclic fatigue effects in a prestressed
structure and intuition doesn't always give the right answer.
Stiffer elements can suffer more than flexy elements.

Spoke tension cycling comes from the fact that the wheel
deforms slightly under load. Motorcycle wheels are
stiffer, but the load is greater, so I don't know how much
the tension cycles per revolution; one would probably have
to do an FEA calculation to get a believable theoretical answer.
Of course, there is an experimental way of doing it,
which is to measure the tension in the bottom spokes
of a loaded wheel vs. the same wheel unloaded.

Ben

[steve]

Post by v***@aol.com
Many thanks for all the replies, it's much appreciated. I'll have to
see if i can find a good 40 hole Sturmey and get it laced with the
suggested spokes with washers and see how many miles it will do. I
really had thought that any spoke would last a couple of thousand,
regardless of installation. Saying that, the lad which i used on the
first two wheels is a bit of a novice. He ground away half the head of
each nipple, so he probably didn't have the correct length spokes to
begin with. Just one question, if 13g straight gauge spokes are prone
to low tension fatigue, do they suffer from the same problem on
motorcycle wheels such as Harleys. Anyone know what the situation is
with motorbikes. When i use to mess around with them, i don't think
that i ever came across a broken spoke. Anyway thanks again for the
replies, i'll try to apply some of the advice and record the results.
cheers, Nick.

I would agree with Jobst. Most motorcycle rims are not only wider and
stiffer but they are also smaller in diameter than a normal bike wheel
which will add to rim stiffness and create a stronger wheel, better
able to handle the forces exerted on it. The other thing to consider
is the larger tires used on a motorcycle. These tires have more air
volume between the rim and the road allowing the rim to experience
less shock from the road.
It would be interesting to know how many spokes a motorcycle wheel
typically has. It seems to me that they have quite a few spokes or at
least more that most bicycle wheels. On the other hand it is a
smaller wheel with thicker spokes which can be very decieving.

Steve

[j***@stanfordalumni.org]

Post by steve

Many thanks for all the replies, it's much appreciated. I'll have
to see if I can find a good 40 hole Sturmey and get it laced with
the suggested spokes with washers and see how many miles it will
do. I really had thought that any spoke would last a couple of
thousand, regardless of installation. Saying that, the lad which I
used on the first two wheels is a bit of a novice. He ground away
half the head of each nipple, so he probably didn't have the
correct length spokes to begin with. Just one question, if 13g
straight gauge spokes are prone to low tension fatigue, do they
suffer from the same problem on motorcycle wheels such as Harleys.
Anyone know what the situation is with motorbikes. When I use to
mess around with them, I don't think that I ever came across a
broken spoke. Anyway thanks again for the replies, I'll try to
apply some of the advice and record the results. cheers, Nick.

I would agree with Jobst. Most motorcycle rims are not only wider
and stiffer but they are also smaller in diameter than a normal bike
wheel which will add to rim stiffness and create a stronger wheel,
better able to handle the forces exerted on it. The other thing to
consider is the larger tires used on a motorcycle. These tires have
more air volume between the rim and the road allowing the rim to
experience less shock from the road. It would be interesting to
know how many spokes a motorcycle wheel typically has. It seems to
me that they have quite a few spokes or at least more that most
bicycle wheels. On the other hand it is a smaller wheel with
thicker spokes which can be very deceiving.

In the days of yore most motorcycles had nominal 19" steel rims with
40 spokes, something that has given way to one piece aluminum wheels
for road while dirt bikes still use 18" rear rims and a 21" front
with, 40 spokes.

Oddball spoke patterns are not the rave in motorcycling as they are
with bicycles and low spoke count gets no prizes.

Jobst Brandt

[c***@comcast.net]

Post by steve

Post by v***@aol.com
Many thanks for all the replies, it's much appreciated. I'll have to
see if i can find a good 40 hole Sturmey and get it laced with the
suggested spokes with washers and see how many miles it will do. I
really had thought that any spoke would last a couple of thousand,
regardless of installation. Saying that, the lad which i used on the
first two wheels is a bit of a novice. He ground away half the head of
each nipple, so he probably didn't have the correct length spokes to
begin with. Just one question, if 13g straight gauge spokes are prone
to low tension fatigue, do they suffer from the same problem on
motorcycle wheels such as Harleys. Anyone know what the situation is
with motorbikes. When i use to mess around with them, i don't think
that i ever came across a broken spoke. Anyway thanks again for the
replies, i'll try to apply some of the advice and record the results.
cheers, Nick.

I would agree with Jobst. Most motorcycle rims are not only wider and
stiffer but they are also smaller in diameter than a normal bike wheel
which will add to rim stiffness and create a stronger wheel, better
able to handle the forces exerted on it. The other thing to consider
is the larger tires used on a motorcycle. These tires have more air
volume between the rim and the road allowing the rim to experience
less shock from the road.
It would be interesting to know how many spokes a motorcycle wheel
typically has. It seems to me that they have quite a few spokes or at
least more that most bicycle wheels. On the other hand it is a
smaller wheel with thicker spokes which can be very decieving.
Steve

Dear Steve,

Trials front and rear, 32 spokes:

Loading Image...

Motocross front 36, rear 32:

Loading Image...

This company offers 32, 36, and 40 hole rims:

http://www.buchananspokes.com/Excel_dimp.htm

Cheers,

Carl Fogel

[c***@comcast.net]

Post by steve

Post by v***@aol.com
Many thanks for all the replies, it's much appreciated. I'll have to
see if i can find a good 40 hole Sturmey and get it laced with the
suggested spokes with washers and see how many miles it will do. I
really had thought that any spoke would last a couple of thousand,
regardless of installation. Saying that, the lad which i used on the
first two wheels is a bit of a novice. He ground away half the head of
each nipple, so he probably didn't have the correct length spokes to
begin with. Just one question, if 13g straight gauge spokes are prone
to low tension fatigue, do they suffer from the same problem on
motorcycle wheels such as Harleys. Anyone know what the situation is
with motorbikes. When i use to mess around with them, i don't think
that i ever came across a broken spoke. Anyway thanks again for the
replies, i'll try to apply some of the advice and record the results.
cheers, Nick.

I would agree with Jobst. Most motorcycle rims are not only wider and
stiffer but they are also smaller in diameter than a normal bike wheel
which will add to rim stiffness and create a stronger wheel, better
able to handle the forces exerted on it. The other thing to consider
is the larger tires used on a motorcycle. These tires have more air
volume between the rim and the road allowing the rim to experience
less shock from the road.
It would be interesting to know how many spokes a motorcycle wheel
typically has. It seems to me that they have quite a few spokes or at
least more that most bicycle wheels. On the other hand it is a
smaller wheel with thicker spokes which can be very decieving.
Steve

Dear Steve,

Trials front and rear, 32 spokes:

http://www.gasgasmotos.es/rcs/trial/tri_2007/300/zoom/07txt300.jpg

Motocross front 36, rear 32:

http://powersports.honda.com/assets/images/model/model_hero_shot/motorcycles/2007/large/CRF450R.jpg

This company offers 32, 36, and 40 hole rims:

http://www.buchananspokes.com/Excel_dimp.htm

Cheers,

Carl Fogel

[Michael Press]

In article
<***@a75g2000cwd.googlegroups.com>
,

Post by v***@aol.com
I do around 150m per week

That won't even get you to the package store/off
license/liquor store.

[v***@aol.com]

cheers Michael, when i say 150m, i meant miles, sorry, ha. I've
managed 240 miles in a week, which on a 1979 Raleigh three speed
weighing 48lbs with fishing gear and me at a gigantic 227lbs is pretty
impressive. Don't build them like that any more, well apart from
people like Mercian. I'm planning to see if i can retro fit a set of
26 1 3/8 wheels with rear oln of 115mm to a King of Mercia. Should be
interesting to see if the mudguards with clear ok with the Marathon
plus tyres.

Post by Michael Press
In article
,

I do around 150m per weekThat won't even get you to the package store/off

license/liquor store.
--
Michael Press

[jim beam]

Post by v***@aol.com
I've had a couple of major spoke failures on my main touring bike which
uses a sturmey Archer AG 36h Dynohub. On the last major failure,
luckily i was at the end of the street. I do around 150m per week, so i
started to think that heavier spokes would be a good idea. With that in
mind i got three wheels rebuilt using 13g generic steel x 36 , 14g DT's
x 40, and 13g Sapim single butted x 36 on a standard AW hub with
washers(all three stainless westrick rims). My plan was to test each
variant, by riding each till failure, in order to sort out the issue
once and for all. I figured that i would get atleast 3k miles out of
the 13g straight/g because the original 14g Raleigh factory spokes had
lasted since 1979 with some 300m per year. Anyway, 823 miles into the
first wheel, i hit first one, then another, small and invisible
potholes, whilst 25 miles out on a trip. Heard a loud snap and then
spent 25 very nervous miles limping home. Hopefully wheel two and three
will fair better.

in my experience, 13g spokes have a longer shank between the head and
elbow - and consequently they're usually used with thicker hub flanges.
use on a normal flange width hub will therefore increase the bending
stress cycle and show early fatigue. that and generic material will not
last. my recommendation is to stick with normal gauge spokes of the
highest quality you can afford and make sure they're a good fit for the
flange.

Post by v***@aol.com
I had a look at the spoke and the fracture surface is almost like
glass, with no signs of trauma or the usual rough fatigue pattern. This
put me in mind of an overly hardened endmill or some such that has
broken through being too brittle. Do these spokes sometimes get over
hardened or perhaps would a slightly softer spoke withstand impact
shocks without failing. Lastly, the Sapim Strong equipped wheel has
been built 4 cross by one of the UK's best wheelbuilders. Unfortunately
he couldn't find any 13g brass washers, so used standard, but slightly
larger nickle plated ones. Looking at the wheel, the spokes are curved
as they are forced to touch the adjacent spoke head upon exit of the
hub and some the washer edges, due to the accuteness of the 4x spoke
angle. Am i right to be worried that this contact will at some time
possibly damage and break the spoke heads? Is there any other way of
making the wheel bullet proof, or will one or two small pot holes
always destroy a wheel?
sorry for the long ramble.
cheers, Nick. England.