wheelbuilding question

jabpn said:

I have recently begun the forray into wheel-building. I
have read a lot of subject matter that states, for rear
wheels, that the non-freewheel side of the wheel will not
be as highly tensioned as the freewheel side. With disc
brakes becoming more and more popular, does this still
hold true?

Yes, for bikes with derailer gearing.

Quoted message said:

It seems to make sense that the rotor side should have
more tension now to provide proper wheel support. Any info
you can send me regarding your experience or knowledge
would be so helpful. All wheel-building websites and books
I've found/read just aren't updated enough to answer the
questions about new technologies in the bicycling
industry.

That's 'cause there's nothing new to update. You'll only
have one disc rotor, which won't take up nearly as much
lateral space as a cassette

Sheldon "No News Is Good News" Brown

(sorry, don't have my quotes collection on this $#!@*!
Wintel box.)

Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
harriscyclery.comharriscyclery.comOpen ↗
Hard-to-find parts shipped Worldwide
captainbike.comcaptainbike.comOpen ↗
Useful articles about bicyces and cycling
sheldonbrown.comsheldonbrown.comOpen ↗

In article <[email hidden]>,

jabpn said:

I have read a lot of subject matter that states, for rear
wheels, that the non-freewheel side of the wheel will not
be as highly tensioned as the freewheel side. With disc
brakes becoming more and more popular, does this still
hold true?

Spoke tension is a vector and the left/right components of
the spokes on both sides must add to 0 for the rim to remain
stationary.

Where the spokes on one side are more angled than the other
their tension has a larger left/right component so the total
tension must be lower on that side.

Total tension on the two sides won't be equal unless the
spokes approach the rim at the same angle. While a disc
wheel can have less difference it's not going to be
symetrical.
--
<a href="poohsticks.orgdrewOpen ↗">Home Page</a

jabpn said:

I have recently begun the forray into wheel-building. I
have read a lot of subject matter that states, for rear
wheels, that the non-freewheel side of the wheel will not
be as highly tensioned as the freewheel side. With disc
brakes becoming more and more popular, does this still
hold true?

yes.

Quoted message said:

It seems to make sense that the rotor side should have
more tension now to provide proper wheel support. Any
info you can send me regarding your experience or
knowledge would be so helpful.

the relative tensions are a function of the angles the
spokes make with the rim, which is in turn determined by
flange spacing. if the flange spacing on a disk hub is
the same as a non-disk hub, the relative tensions will
be the same.

Quoted message said:

All wheel-building websites and books I've found/read
just aren't updated enough to answer the questions about
new technologies in the bicycling industry.

it's not new technology, but you're right, this is not
covered in any book i've seen. however, if you want to look
at the math, it's in the latest version of damon renard's
spoke calculator spreadsheet.

[email hidden] (jabpn) wrote in message news:<[email hidden]>...

Quoted message said:

I have recently begun the forray into wheel-building. I
have read a lot of subject matter that states, for rear
wheels, that the non-freewheel side of the wheel will not
be as highly tensioned as the freewheel side. With disc
brakes becoming more and more popular, does this still
hold true?

Yes. The rotor mounting stuff moves that flange inboard a
bit, but not as much as the cassette.

Quoted message said:

It seems to make sense that the rotor side should have
more tension now to provide proper wheel support. Any info
you can send me regarding your experience or knowledge
would be so helpful.

That's true - the more tension you can bring to bear
(before destroying the rim) the better. Read "The Bicycle
Wheel" by Jobst Brandt. Lots of good info on the "why" of
wheelbuilding, and a nice section of "how" as well. He does
not specifically address disk brakes, but from the info,
you can determine how the spokes should be to best support
the loads.

"Zinn and the Art of Mountain Bike Maintenance" by Lenard
Zinn has a section on wheelbuilding that has a nice how-to
that directly addresses disk brake wheels.

Quoted message said:

All wheel-building websites and books I've found/read
just aren't updated enough to answer the questions about
new technologies in the bicycling industry.

The Zinn book is nice - it has other stuff that's useful,
like an appendix containing a decent torque table.

If you are interested in reading some long-winded drivel I
have written recently, find the thread in this group titled
"Wheelbuilding Question(s)". One of the things that shocked
me was that for my rim and hub choice, the difference
between the length of the longest and shortest spokes and
was 1.3mm. IOW, one length to do all of the spoking. Sort of
counter-intuitive, but the front wheel built up just fine,
and I suspect that the rear will build up equally well.

Good luck, and tell us how things work out.
--
Jonesy

Jonesy said:

[email hidden] (jabpn) wrote in message
news:<[email hidden]>...

Quoted message said:

I have recently begun the forray into wheel-building. I
have read a lot of subject matter that states, for rear
wheels, that the non-freewheel side of the wheel will not
be as highly tensioned as the freewheel side. With disc
brakes becoming more and more popular, does this still
hold true?

Yes. The rotor mounting stuff moves that flange inboard a
bit, but not as much as the cassette.

Quoted message said:

It seems to make sense that the rotor side should have
more tension now to provide proper wheel support. Any info
you can send me regarding your experience or knowledge
would be so helpful.

That's true - the more tension you can bring to bear
(before destroying the rim) the better. Read "The Bicycle
Wheel" by Jobst Brandt.

i know that "high tension" recommendation is "in the book"
and often repeated here, but it's a fundamentally flawed
piece of advice. the closer a rim is operated to it's yield
point, the less will be its fatigue life, with the kind of
results reported here yesterday:

mixednutsband.comcrack4.jpgOpen ↗

just because a rim doesn't fail with static load, doesn't
mean it can take the fatigue load. that's why there are so
many reliability complaints here on r.b.t.

in addition, as can be seen in damon rinard's experiments,
increasing spoke tension makes absolutely no difference to
lateral strength. see:

sheldonbrown.comtension.gifOpen ↗

original page:
sheldonbrown.comindex.htmOpen ↗

max spoke tension is determined by the rim's manufacturer.
something like a mavic open pro has a recommended max
tension of 100-110 kgf.

Quoted message said:

Lots of good info on the "why" of wheelbuilding, and a
nice section of "how" as well. He does not specifically
address disk brakes, but from the info, you can determine
how the spokes should be to best support the loads.

"Zinn and the Art of Mountain Bike Maintenance" by Lenard
Zinn has a section on wheelbuilding that has a nice how-to
that directly addresses disk brake wheels.

Quoted message said:

All wheel-building websites and books I've found/read
just aren't updated enough to answer the questions about
new technologies in the bicycling industry.

The Zinn book is nice - it has other stuff that's useful,
like an appendix containing a decent torque table.

If you are interested in reading some long-winded drivel I
have written recently, find the thread in this group
titled "Wheelbuilding Question(s)". One of the things that
shocked me was that for my rim and hub choice, the
difference between the length of the longest and shortest
spokes and was 1.3mm. IOW, one length to do all of the
spoking. Sort of counter-intuitive, but the front wheel
built up just fine, and I suspect that the rear will build
up equally well.

Good luck, and tell us how things work out.

jab-<< that the non-freewheel side of the wheel will not be
as highly tensioned as the freewheel side. With disc brakes
becoming more and more popular, does this still hold true?

Quoted message said:

Quoted message said:

<BR><BR>

Yes but with hub flange placement, the tension between left
and right is closer to the same.

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St.
Boulder, CO, 80302
(303)440-3535 vecchios.comvecchios.comOpen ↗ "Ruote convenzionali
costruite eccezionalmente bene"

[email hidden] (jabpn) wrote in message news:<[email hidden]>...

Thanks all for the advice. I'll let you know how it goes as
soon as my supplies come in and I can start. I'm actually
replacing my Deore Disc hub with an Deore XT 756 Disc hub.
(figured I might as well upgrade now rather than later.
Although I'll probably stay with my X223 Mavic rims instead
of, say, Rhino Lites for now). I hate downtime and can't
wait to get back on the bike!!

On Fri, 09 Jul 2004 22:09:48 -0700, jim beam <[email hidden]>

Quoted message said:

in addition, as can be seen in damon rinard's experiments,
increasing spoke tension makes absolutely no difference to
lateral strength. see:

sheldonbrown.comtension.gifOpen ↗

original page:
sheldonbrown.comindex.htmOpen ↗

Careful; the info on that page may not have much to do with
a wheel's lateral strength. Here's a quote from that link:

"It must be emphasized that wheel stiffness is not wheel
strength, and in fact may be unrelated to it. I am measuring
stiffness, not strength."

Also, and this statement doesn't appear to be backed up with
any measurements on that page, but he also says (under
question #1):

"A wheel whose spokes become slack while riding is a weak
wheel, because slack spokes cannot support the rim. This
can be avoided to a large extent by building wheels with
tighter spokes."

However, I wonder if Jobst's "slight taco" method is only
one potential upper limit on spoke tension. Rims cracking in
fatigue, nipples rounding, hub flanges breaking, etc. may be
some others.

But I think we agree in practice. Without lots of
experimentation, it's difficult for me to predict the
fatigue stuff before I build the wheel, so I generally
follow the manufacturer's specifications when available.

jim beam said:

in addition, as can be seen in damon rinard's experiments,
increasing spoke tension makes absolutely no difference to
lateral strength. see:

sheldonbrown.comtension.gifOpen ↗

original page:
sheldonbrown.comindex.htmOpen ↗

Rinard's wheel test did not test (lateral) strength, as he
stated in his first paragraph: "I am measuring stiffness,
not strength." His test of measuring lateral stiffness at
varying static spoke tension mainly serves to confirm
Hooke's Law.

However, if you take a closer look at the graph, you'll
notice that the deflection increases dramatically when he
backs the tension off below a certain threshold. This
increase in deflection shows a wheel that is more likely to
fail under load. Although Rinard is using a fixed load, it
can be inferred from this data that increased spoke tension
can increase the strength of a wheel. Indeed, you're
supposition that "increasing spoke tension makes absolutely
no difference in lateral strength" is directly contradicted
by Rinard's conclusion from his test. From the web page
referenced above:

"A wheel whose spokes become slack while riding is a weak
wheel, because slack spokes cannot support the rim. This can
be avoided to a large extent by building wheels with tighter
spokes. If spokes are tighter initially, then the sudden
increase in flexibility shown in data points 9 and 10 is
less likely to occur in use because a tighter wheel can bear
a higher load before spokes become slack."

Quoted message said:

max spoke tension is determined by the rim's manufacturer.
something like a mavic open pro has a recommended max
tension of 100-110 kgf.

While one might like to think that rim manufacturers would
recommend maximum tensions for their rims, I have never
actually seen a manufacturer actually publish such data.
Where did you get the value for the Mavic Open Pro?

On the other hand, the concept of excess spoke tension is
often used as a dodge by manufacturers to avoid warranty
replacement for cracked rims. In none of the cases that I
have seen where a manufacturer's rep. denied a warranty by
claiming "the spoke tension must have been too high", no
measurement of actual spoke tension has been made to base
that claim on, nor has the rep. been able to state what the
recommended max. tension should be. The "excess tension"
argument has simply been used as an easy out.

Mark McMaster [email hidden]

Mark McMaster said:

jim beam said:

in addition, as can be seen in damon rinard's
experiments, increasing spoke tension makes absolutely no
difference to lateral strength. see:

sheldonbrown.comtension.gifOpen ↗

original page:
sheldonbrown.comindex.htmOpen ↗

Rinard's wheel test did not test (lateral) strength, as he
stated in his first paragraph: "I am measuring stiffness,
not strength." His test of measuring lateral stiffness at
varying static spoke tension mainly serves to confirm
Hooke's Law.

hookes law merely states that deformation is directly
proportional to load below yield - the definition of elastic
deformation. it's no predictor of yield or modulus, both of
which are measures of "strength". by that same argument,
increasing tension does not increase strength just the same
as it does not increase stiffness.

Quoted message said:

However, if you take a closer look at the graph, you'll
notice that the deflection increases dramatically when he
backs the tension off below a certain threshold. This
increase in deflection shows a wheel that is more likely
to fail under load.

that's an assumption, not a fact. the deflection increases,
for slack spokes /because/ they're slack. if you're towing a
car with a slack rope, the distance between the two cars
will increase until the rope becomes taught. then the
distance between the two cars is essentially fixed and
subject only to minor stretching of the rope - many orders
of magnitude less that slack take-up.

Quoted message said:

Although Rinard is using a fixed load, it can be inferred
from this data that increased spoke tension can increase
the strength of a wheel.

"inferred" how? the material does not change - this material
still has to obey hookes law until it yields. increasing
load merely makes it bend further. if you think about it,
pre-tension serves to reduce the load capacity of a
component not increase it.

Quoted message said:

Indeed, you're supposition that "increasing spoke tension
makes absolutely no difference in lateral strength" is
directly contradicted by Rinard's conclusion from his
test. From the web page referenced above:

"A wheel whose spokes become slack while riding is a weak
wheel, because slack spokes cannot support the rim. This
can be avoided to a large extent by building wheels with
tighter spokes. If spokes are tighter initially, then the
sudden increase in flexibility shown in data points 9 and
10 is less likely to occur in use because a tighter wheel
can bear a higher load before spokes become slack."

there's no contradiction. the left part of the graph is
essentially a flat line. leftwards is increasing tension.
once you're in the flat line region, increasing tension is
not increasing lateral stiffness.

Quoted message said:

Quoted message said:

max spoke tension is determined by the rim's
manufacturer. something like a mavic open pro has a
recommended max tension of 100-110 kgf.

While one might like to think that rim manufacturers would
recommend maximum tensions for their rims, I have never
actually seen a manufacturer actually publish such data.
Where did you get the value for the Mavic Open Pro?

mavic's tech service department - i called them. you can
also google this group - peter chisholm can quote you
tensions for a number of rims.

Quoted message said:

On the other hand, the concept of excess spoke tension is
often used as a dodge by manufacturers to avoid warranty
replacement for cracked rims.

i can see this might be a dodge sometimes, at least at the
retail level, but on a trade basis [the majority of the
business] a manufacturer is entitled to not be second-
guessed by a consumer about use in service. if an diving
cylinder manufacturer specified a certain maximum charge
pressure, but a user chose to exceed that manufacturer's
limit because they wanted to extend their dive time, who
would be liable for the resulting cylinder failure? how
about a retailer recommending excess pressure to a consumer
because they thought they knew better than the manufacturer?

Quoted message said:

In none of the cases that I have seen where a
manufacturer's rep. denied a warranty by claiming "the
spoke tension must have been too high", no measurement of
actual spoke tension has been made to base that claim on,

how are you going to measure original tension once the rim
has failed and slackened the spokes? you /can/ research the
s-n fatigue graph for a component and map out cycles to
failure for each load increment. once you know stress and
the curve, you can accurately predict cycles to failure.
likewise, if you can judge cycles to failure from braking
surface wear, you know very closely the load to which the
rim has been subject. and that can also be referenced back
to the rim's batch number and q.c. lab tests. if it's not
from a defective batch, then the rim /has/ to have been
subect to use outside of spec.

Quoted message said:

nor has the rep. been able to state what the recommended
max. tension should be.

as stated above, mavic service dept had no problem telling
me recommended tensions.

Quoted message said:

The "excess tension" argument has simply been used as an
easy out.

this may be true, but it may not. how many times have you
been in a store and watched other people arguing over
something petty like returning a used garment? 9 times out
of 10, the returnee with attitude will be given a hard time,
just because the store personnel hate being treated like
dirt, not because there isn't a valid argument.

"jim beam" <[email hidden]> wrote

Quoted message said:

Jonesy wrote:

Quoted message said:

Quoted message said:

That's true - the more tension you can bring to bear
(before destroying the rim) the better. Read "The
Bicycle Wheel" by Jobst Brandt.

i know that "high tension" recommendation is "in the book"
and often repeated here, but it's a fundamentally flawed
piece of advice.

It's also a misquote. The technique Jobst describes is
qualified to work only with lightweight (430 g or less), 36
spoke rims.

Quoted message said:

the closer a rim is operated to it's yield point, the
less will be its fatigue life, with the kind of results
reported here yesterday:

mixednutsband.comcrack4.jpgOpen ↗

just because a rim doesn't fail with static load, doesn't
mean it can take the fatigue load. that's why there are so
many reliability complaint here on r.b.t.

Historically, the dominant wheel problems have been spoke
breakage & wheels coming out of true. Cracking of the spoke
bed is strictly a matter of rim design and spoke tension.
For wheels like the one shown, the use of a tensiometer
would seem mandatory.

Quoted message said:

in addition, as can be seen in damon rinard's experiments,
increasing spoke tension makes absolutely no difference to
lateral strength. see:

sheldonbrown.comtension.gifOpen ↗

original page:
sheldonbrown.comindex.htmOpen ↗

I think you are confusing strength and stiffness. The
rationale for high spoke tension is that radial, not
lateral, loads cause the spoke to lose tension, so the spoke
tension (& number of spokes) determines the load carrying
capacity of the wheel. If a wheel is loaded beyond that, the
spokes may become de-tensioned enough to either cause wheel
collapse or nipple unscrewing.

Peter Cole said:

"jim beam" <[email hidden]> wrote

Quoted message said:

Jonesy wrote:

Quoted message said:

Quoted message said:

That's true - the more tension you can bring to bear
(before destroying the rim) the better. Read "The Bicycle
Wheel" by Jobst Brandt.

i know that "high tension" recommendation is "in the book"
and often repeated here, but it's a fundamentally flawed
piece of advice.

It's also a misquote. The technique Jobst describes is
qualified to work only with lightweight (430 g or less),
36 spoke rims.

has he ever said that? i don't have his book in front of me;
i can't recall such a qualification, but i've seen jonsey's
kind of statement here many times.

Quoted message said:

Quoted message said:

the closer a rim is operated to it's yield point, the
less will be its fatigue life, with the kind of results
reported here yesterday:

mixednutsband.comcrack4.jpgOpen ↗

just because a rim doesn't fail with static load, doesn't
mean it can take the fatigue load. that's why there are so
many reliability complaint here on r.b.t.

Historically, the dominant wheel problems have been spoke
breakage & wheels coming out of true. Cracking of the
spoke bed is strictly a matter of rim design and spoke
tension. For wheels like the one shown, the use of a
tensiometer would seem mandatory.

good observations.

Quoted message said:

Quoted message said:

in addition, as can be seen in damon rinard's experiments,
increasing spoke tension makes absolutely no difference to
lateral strength. see:

sheldonbrown.comtension.gifOpen ↗

original page:
sheldonbrown.comindex.htmOpen ↗

I think you are confusing strength and stiffness. The
rationale for high spoke tension is that radial, not
lateral, loads cause the spoke to lose tension, so the
spoke tension (& number of spokes) determines the load
carrying capacity of the wheel. If a wheel is loaded
beyond that, the spokes may become de-tensioned enough to
either cause wheel collapse or nipple unscrewing.

i've read the radial loading argument of high tension [and i
know the difference between strength & stiffness!].
regarding lateral loading, this adds to the spoke pre
tension on one side and subtracts from the other. radial
loads subtract only. if a spoke has a yield strength of say
300kg, preloading it to 200kg only gives 100kg of lateral
load before yield. if the spokes have 100kg preload, it
means they can take twice as much lateral.

i want to be clear - i'm not advocating "too low tension" -
i'm saying that tension needs to be within spec, not this
nebulous unscientific concept of "as high as the rim can
bear". agreed, too low tension can lead to nipple
unscrewing, but i guess that's why spoke manufacturers sell
threadlock & self-locking nipples.

"jim beam" <[email hidden]> wrote

Quoted message said:

Peter Cole said:

It's also a misquote. The technique Jobst describes is
qualified to work

only

Quoted message said:

Quoted message said:

with lightweight (430 g or less), 36 spoke rims.

has he ever said that? i don't have his book in front of
me; i can't recall such a qualification, but i've seen
jonsey's kind of statement here many times.

I wrote that with the book in front of me, it's stated
very clearly.

Quoted message said:

i've read the radial loading argument of high tension [and
i know the difference between strength & stiffness!].

OK, it's really the only argument Jobst makes.

Quoted message said:

regarding lateral loading, this adds to the spoke pre
tension on one side and subtracts from the other. radial
loads subtract only. if a spoke has a yield strength of
say 300kg, preloading it to 200kg only gives 100kg of
lateral load before yield. if the spokes have 100kg
preload, it means they can take twice as much lateral.

This lateral load argument doesn't really have any practical
considerations.

Quoted message said:

i want to be clear - i'm not advocating "too low tension"
- i'm saying that tension needs to be within spec, not
this nebulous unscientific concept of "as high as the rim
can bear". agreed, too low tension can lead to nipple
unscrewing, but i guess that's why spoke manufacturers
sell threadlock & self-locking nipples.

The more serious consequence is that the wheel can become
unstable and buckle.

jim beam said:

Mark McMaster said:

jim beam said:

in addition, as can be seen in damon rinard's
experiments, increasing spoke tension makes absolutely
no difference to lateral strength. see:

sheldonbrown.comtension.gifOpen ↗

original page:
sheldonbrown.comindex.htmOpen ↗

Rinard's wheel test did not test (lateral) strength, as
he stated in his first paragraph: "I am measuring
stiffness, not strength." His test of measuring lateral
stiffness at varying static spoke tension mainly serves
to confirm Hooke's Law.

hookes law merely states that deformation is directly
proportional to load below yield - the definition of
elastic deformation. it's no predictor of yield or
modulus, both of which are measures of "strength". by that
same argument, increasing tension does not increase
strength just the same as it does not increase stiffness.

No argument. Rinard's test just shows that the existence of
a static pre-load doesn't change the wheel stiffness.

Quoted message said:

Quoted message said:

However, if you take a closer look at the graph, you'll
notice that the deflection increases dramatically when he
backs the tension off below a certain threshold. This
increase in deflection shows a wheel that is more likely
to fail under load.

that's an assumption, not a fact. the deflection
increases, for slack spokes /because/ they're slack. if
you're towing a car with a slack rope, the distance
between the two cars will increase until the rope
becomes taught. then the distance between the two cars
is essentially fixed and subject only to minor
stretching of the rope - many orders of magnitude less
that slack take-up.

Poor analogy - as the the wheel is continued to be loaded
with slack spokes, there is no point when the spokes
suddenly start supporting the wheel.

Typical shallow section rims are not strong enough on their
own to support the momentary high loads often experienced
when cycling. The rim requires the support of the spokes.
Slackened spokes can no longer contribute support to the
spokes, and the rim must bear the load. Since the
unsupported rim can not bear as much load without damage, a
wheel low static spoke tension is more likely to be damaged
under a high momentary load.

Quoted message said:

Quoted message said:

Although Rinard is using a fixed load, it can be inferred
from this
data that increased spoke tension can increase the
strength of a wheel.

"inferred" how? the material does not change - this
material still has to obey hookes law until it yields.
increasing load merely makes it bend further. if you think
about it, pre-tension serves to reduce the load capacity
of a component not increase it.

The graphs shows that at at some minimum tension, some of
the spokes slacken and no longer can contribute to
supporting the rim. It can be inferred that at a higher
static spoke tension, the spokes will not slacken until a
higher applied load. Since a wheel with all spokes still
under tension is a stronger wheel, than a wheel with higher
static spoke tension can support a higher load.

Quoted message said:

Quoted message said:

Indeed, you're supposition that "increasing spoke
tension makes absolutely no difference in lateral
strength" is directly contradicted by Rinard's
conclusion from his test. From the web page referenced
above:

"A wheel whose spokes become slack while riding is a weak
wheel, because slack spokes cannot support the rim. This
can be avoided to a large extent by building wheels with
tighter spokes. If spokes are tighter initially, then the
sudden increase in flexibility shown in data points 9 and
10 is less likely to occur in use because a tighter wheel
can bear a higher load before spokes become slack."

there's no contradiction. the left part of the graph is
essentially a flat line. leftwards is increasing tension.
once you're in the flat line region, increasing tension is
not increasing lateral stiffness.

There's more to it than simply stiffness. The sharp decrease
in stiffness occurs at the point when some of the spokes no
longer contribute to supporting the wheel. You claim seem to
claim spoke slackening make no difference in wheel strength
- Damon Rinard claims it does (and I agree with him).

Mark McMaster [email hidden]

jim beam <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

Peter Cole said:

"jim beam" <[email hidden]> wrote

Quoted message said:

Jonesy wrote:

Quoted message said:

>That's true - the more tension you can bring to bear
>(before destroying the rim) the better. Read "The
>Bicycle Wheel" by Jobst Brandt.

i know that "high tension" recommendation is "in the
book" and often repeated here, but it's a fundamentally
flawed piece of advice.

It's also a misquote. The technique Jobst describes is
qualified to work only with lightweight (430 g or less),
36 spoke rims.

has he ever said that? i don't have his book in front of
me; i can't recall such a qualification, but i've seen
jonsey's kind of statement here many times.

It was a gross generalization. It was not meant to be
definitive, which is why I suggested further reading.

[snip]

Quoted message said:

i want to be clear - i'm not advocating "too low tension"
- i'm saying that tension needs to be within spec, not
this nebulous unscientific concept of "as high as the rim
can bear".

If one was pedantic, they would say that "within spec" is
"as high as the rim can bear." But I was not being specific.

Quoted message said:

agreed, too low tension can lead to nipple unscrewing, but
i guess that's why spoke manufacturers sell threadlock &
self-locking nipples.

It seems to me that, on a properly-tensioned spoke with no
wind-up, threadlocking materials are completely unnecessary.

My apologies for not being more specific. After being
berated for being long-winded, I'm trying to cut down. I
guess being specific has some cost.

My intent was to steer the OP toward some reading materials.
Mr. Beam, if you would be so kind, why don't you assemble
the tension specs for rims such that you may in the future
warn folks about over-tensioning (past rim manufacturer's
specs). That would be a fantastic resource, and easier than
arguing the theoretical materials science behind your
commentary - something that might not help a poor
wheelbuilder like myself.
--
Jonesy
--
Jonesy

Peter Cole said:

"jim beam" <[email hidden]> wrote

Quoted message said:

Peter Cole said:

It's also a misquote. The technique Jobst describes is
qualified to work

only

Quoted message said:

Quoted message said:

with lightweight (430 g or less), 36 spoke rims.

has he ever said that? i don't have his book in front of
me; i can't recall such a qualification, but i've seen
jonsey's kind of statement here many times.

I wrote that with the book in front of me, it's stated
very clearly.

Quoted message said:

i've read the radial loading argument of high tension [and
i know the difference between strength & stiffness!].

OK, it's really the only argument Jobst makes.

Quoted message said:

regarding lateral loading, this adds to the spoke pre
tension on one side and subtracts from the other. radial
loads subtract only. if a spoke has a yield strength of
say 300kg, preloading it to 200kg only gives 100kg of
lateral load before yield. if the spokes have 100kg
preload, it means they can take twice as much lateral.

This lateral load argument doesn't really have any
practical considerations.

the only consideration is that if the spoke tension is too
high, the rim is much more prone to taco. the only rim i've
ever tacoed [not caused by a car] was first ride immediately
after i'd just built a wheel with "tension as high as the
rim can bear". downhill, bump, pretzel, long walk home. the
bump wasn't even enough to flat the tire.

Quoted message said:

Quoted message said:

i want to be clear - i'm not advocating "too low tension"
- i'm saying that tension needs to be within spec, not
this nebulous unscientific concept of "as high as the rim
can bear". agreed, too low tension can lead to nipple
unscrewing, but i guess that's why spoke manufacturers
sell threadlock & self-locking nipples.

The more serious consequence is that the wheel can become
unstable and buckle.

i would have thought that, but i rode mtb for the best part
of a year with a guy whose rear wheel was always making an
irritating grinding noise. eventually, i pursuaded him to
let me take it home for examination. i was shocked to find
that all the spokes were so loose, they were almost slack -
the grinding was the spoke crossings moving against each
other as the hub "sank" relative to center on load - flat
spots on each spoke at that point. and the damnedest thing
of all was that this wheel was as true as i've ever seen!

he rides real hard & loves the fast bumpy downhill stuff, so
there was /plenty/ of opportunity for his wheel to have
failed. this one instance is not enough to demonstrate
proof, but it's worth further investigation.