SPOKE LENGTH IN NIPPLE



D

datakoll

Guest
A PHOTO OF a correct spoke length as the spoke end sits in the mounted
nipple.
Notice the length is NOT at the ERD position.

the author:

"Although the nipple
brand we currently prefer can thread all the way through, not all
brands
can. Some nipple threads bind terribly as the spoke extends into the
slot. We shoot for a length just at the inside edge of the rim or at
the
start of the slot as shown here:

http://www.yellowjersey.org/photosfromthepast/SPOKDEPT.JPG

If you work with any given spoke calculation software regularly, you
can
tweak your results as finely as you like, down to that 1mm difference
between bottom of slot and top of slot.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971 "
 
datakoll wrote:
> A PHOTO OF a correct spoke length as the spoke end sits in the mounted
> nipple.
> Notice the length is NOT at the ERD position.


then your problem has been confusion over what "erd" means. if you use
the rim manufacturer's erd data, and one of the spoke calculators, the
result will be perfect spoke length, as per andrew's photo. every time.



>
> the author:
>
> "Although the nipple
> brand we currently prefer can thread all the way through, not all
> brands
> can. Some nipple threads bind terribly as the spoke extends into the
> slot. We shoot for a length just at the inside edge of the rim or at
> the
> start of the slot as shown here:
>
> http://www.yellowjersey.org/photosfromthepast/SPOKDEPT.JPG
>
> If you work with any given spoke calculation software regularly, you
> can
> tweak your results as finely as you like, down to that 1mm difference
> between bottom of slot and top of slot.
> --
> Andrew Muzi
> www.yellowjersey.org
> Open every day since 1 April, 1971 "
>
>
 
On 2008-02-02, jim beam <[email protected]> wrote:
> datakoll wrote:
>> A PHOTO OF a correct spoke length as the spoke end sits in the mounted
>> nipple.
>> Notice the length is NOT at the ERD position.

>
> then your problem has been confusion over what "erd" means. if you use
> the rim manufacturer's erd data, and one of the spoke calculators, the
> result will be perfect spoke length, as per andrew's photo. every time.


OK in that case I'm still confused about ERD means.

I think Andrew's photo is what you should get if you use Mavic's "spoke
support diameter", which is about 3mm shorter than the ERD, as defined
by Brandt, and also as used in the comment in spocalc.xls I mentioned
earlier.

I also think Andrew's photo shows an ideal spoke length.

[...]
>> "Although the nipple
>> brand we currently prefer can thread all the way through, not all
>> brands
>> can. Some nipple threads bind terribly as the spoke extends into the
>> slot. We shoot for a length just at the inside edge of the rim or at
>> the
>> start of the slot as shown here:
>>
>> http://www.yellowjersey.org/photosfromthepast/SPOKDEPT.JPG
 
Ben C wrote:
> On 2008-02-02, jim beam <[email protected]> wrote:
>> datakoll wrote:
>>> A PHOTO OF a correct spoke length as the spoke end sits in the mounted
>>> nipple.
>>> Notice the length is NOT at the ERD position.

>> then your problem has been confusion over what "erd" means. if you use
>> the rim manufacturer's erd data, and one of the spoke calculators, the
>> result will be perfect spoke length, as per andrew's photo. every time.

>
> OK in that case I'm still confused about ERD means.


"erd" is simple enough - it's what "effective" means that's unclear.
maybe that's why mavic call it "spoke support" - since they clearly
haven't read jobst's book and are untainted by its terminological
inexactitudes.


>
> I think Andrew's photo is what you should get if you use Mavic's "spoke
> support diameter", which is about 3mm shorter than the ERD, as defined
> by Brandt, and also as used in the comment in spocalc.xls I mentioned
> earlier.
>
> I also think Andrew's photo shows an ideal spoke length.


indeed.

you can use longer if you want but it gives no latitude for further
adjustment if a problem arises at a later date, and there are certainly
no mechanical benefits.

>
> [...]
>>> "Although the nipple
>>> brand we currently prefer can thread all the way through, not all
>>> brands
>>> can. Some nipple threads bind terribly as the spoke extends into the
>>> slot. We shoot for a length just at the inside edge of the rim or at
>>> the
>>> start of the slot as shown here:
>>>
>>> http://www.yellowjersey.org/photosfromthepast/SPOKDEPT.JPG
 
jim beam wrote:
> Ben C wrote:
>> On 2008-02-02, jim beam <[email protected]> wrote:
>>> datakoll wrote:
>>>> A PHOTO OF a correct spoke length as the spoke end sits in the
>>>> mounted nipple. Notice the length is NOT at the ERD position.
>>> then your problem has been confusion over what "erd" means. if
>>> you use the rim manufacturer's erd data, and one of the spoke
>>> calculators, the result will be perfect spoke length, as per
>>> andrew's photo. every time.

>>
>> OK in that case I'm still confused about ERD means.

>
> "erd" is simple enough - it's what "effective" means that's unclear.
> maybe that's why mavic call it "spoke support" - since they clearly
> haven't read jobst's book and are untainted by its terminological
> inexactitudes.


Now I'm confused. I thought the ERD was measured from opposite nipple
seats in the rim and was \exactly\ the number that determines spoke
length, eliminating the tyre seat nipple support difference. Thus
double wall, nipple seats et al, do not matter, the ERD is
the figure you need to know for spoke lengths.

So, wrt above, the "spoke support" would seem to me to be the ERD and
everyone is happy.

Can it be that such a fundamental number for building a wheel has no
true definition?
 
Tosspot wrote:
> jim beam wrote:
>> Ben C wrote:
>>> On 2008-02-02, jim beam <[email protected]> wrote:
>>>> datakoll wrote:
>>>>> A PHOTO OF a correct spoke length as the spoke end sits in the
>>>>> mounted nipple. Notice the length is NOT at the ERD position.
>>>> then your problem has been confusion over what "erd" means. if
>>>> you use the rim manufacturer's erd data, and one of the spoke
>>>> calculators, the result will be perfect spoke length, as per
>>>> andrew's photo. every time.
>>>
>>> OK in that case I'm still confused about ERD means.

>>
>> "erd" is simple enough - it's what "effective" means that's unclear.
>> maybe that's why mavic call it "spoke support" - since they clearly
>> haven't read jobst's book and are untainted by its terminological
>> inexactitudes.

>
> Now I'm confused. I thought the ERD was measured from opposite nipple
> seats in the rim and was \exactly\


"\" not "/"??? you've been playing with windoze _way_ too much my friend.


> the number that determines spoke
> length, eliminating the tyre seat nipple support difference. Thus
> double wall, nipple seats et al, do not matter, the ERD is
> the figure you need to know for spoke lengths.


"erd" is calculation input. you decide the result you want it to give.


>
> So, wrt above, the "spoke support" would seem to me to be the ERD and
> everyone is happy.


"erd" is calculation input. see above.

>
> Can it be that such a fundamental number for building a wheel has no
> true definition?
 
TAKE A NEW SPOKE AND A NEW NIPPLE, nipples here are 16mm DT, 2.0 DT 14
Ga spokes, fully thread nipple on spoke and where is that spoke
endwhen nipple's fully threaded?

listen, "how could a basic number like an ERD lead to global
disaster"? right! it's wrong, miscommunicated, misused or I'm flatout
stupid and that's why I started the post subject.

an unanswered question: why is the spoke end specified as that deep in
the nipple and close to exhausting the threading? WHAT'S THE FLIPPING
PURPOSE?
 
datakoll wrote:
> TAKE A NEW SPOKE AND A NEW NIPPLE, nipples here are 16mm DT, 2.0 DT 14
> Ga spokes, fully thread nipple on spoke and where is that spoke
> endwhen nipple's fully threaded?


no, you need to think "where is the rim bed". the spoke length is the
variable, not the rim diameter.

>
> listen, "how could a basic number like an ERD lead to global
> disaster"? right! it's wrong, miscommunicated, misused or I'm flatout
> stupid and that's why I started the post subject.


dude, you're saying that you're having no luck because the spoke
lengths, as measured by the method you're using, don't work out right.
we're saying that you'll get the right spoke length every single time if
you apply the math.


>
> an unanswered question: why is the spoke end specified as that deep in
> the nipple and close to exhausting the threading? WHAT'S THE FLIPPING
> PURPOSE?


to allow you to lace it, then tighten it! a tensioned wheel is full of
elastic strain - it's simply impossible to lace it to within three
threads of final tension. the long thread allows it to be connected
together, then adjusted to spec.
 
datakoll said:

[URL=http://www.sheldonbrown.com/rinard/spocalc.htm#MeasureHubAndRim]

You take the rim you want to get the ERD on and use the nipples for the measurement you will use for the build: thread the spokes into the nipples like you want them to be in the finished build.
There are different preferences as to where you want the end of the spoke to be in the nipple and certainly are different ways nipples interface with different rim holes and permit the spokes penetration into the nipple. I agree with the question of the "PURPOSE" issue, but I mostly use spokes that are available in 2 mm incremental length differences; thus, where the end of the spoke ends up in the slot differs.
 
jim beam wrote:
> Tosspot wrote:
>> jim beam wrote:
>>> Ben C wrote:
>>>> On 2008-02-02, jim beam <[email protected]> wrote:
>>>>> datakoll wrote:
>>>>>> A PHOTO OF a correct spoke length as the spoke end sits in the
>>>>>> mounted nipple. Notice the length is NOT at the ERD position.
>>>>> then your problem has been confusion over what "erd" means. if
>>>>> you use the rim manufacturer's erd data, and one of the spoke
>>>>> calculators, the result will be perfect spoke length, as per
>>>>> andrew's photo. every time.
>>>>
>>>> OK in that case I'm still confused about ERD means.
>>>
>>> "erd" is simple enough - it's what "effective" means that's unclear.
>>> maybe that's why mavic call it "spoke support" - since they clearly
>>> haven't read jobst's book and are untainted by its terminological
>>> inexactitudes.

>>
>> Now I'm confused. I thought the ERD was measured from opposite nipple
>> seats in the rim and was \exactly\

>
> "\" not "/"??? you've been playing with windoze _way_ too much my friend.


SUSE 10.3, but anyhow it's not a discussion about OS's.

>> the number that determines spoke
>> length, eliminating the tyre seat nipple support difference. Thus
>> double wall, nipple seats et al, do not matter, the ERD is
>> the figure you need to know for spoke lengths.

>
> "erd" is calculation input. you decide the result you want it to give.


But the output is the spoke length, if I knew the spoke length I could
calculate the ERD, but I don't know the spoke length, so which ERD do I
choose?

My point was, surely it's defined? Actually, I'm ****** and I'm going
to bed, thoroughly confused about whether a manufacturers ERD is to be
trusted or is just a number they dreamed up.

I'm going to be dreaming spokes :(

<snip for brevity>
 
No Beam, the question is not does the math work out right, the
question is are the MO people capable of using spoke calc. And why
not?
The results of this survey, limited as it is to the usual group of
cranks, screwballs, gyrogearloosi, and incompetents, head in the
direction of how is the ERD described in English.

The ERD is snot the spoke length. Spoke length is less than ERD. BUT!
spoke length is continuously described as ERD. That's the impression I
go away with.

If you thread the nipple onto the spoke you will see the nipple seated
onto the rim at the (average) ERD has no more thread capacity.

That was the question I asked. Where is the spoke end minus the ERD?
And the answer came back: The spoke end is the ERD. read it!

Like the ship is going down on defining the ERD for computer entry
data but then the ERD becomes the spoke length: forgetabboutit.

Someone go thru 10 spoke calcs reading if the calcs say what the ERD
is.

what's the purpose? the question is: what's the purpose of approaching
the ERD so closely like its a game of chicken (?!) getting the spoke
end right on top the ERD reduces the spokes chances for adjustment as
you just ran the spoke out of threads. So quack deduct 3mm from ERD.

I'm inclined to get a spoke length that touches the inside eyelet.
that's a good -3mm from ERD-and useful in my experience for HD touring
and long mileage wheel use.
 
Tosspot wrote:
> jim beam wrote:
>> Tosspot wrote:
>>> jim beam wrote:
>>>> Ben C wrote:
>>>>> On 2008-02-02, jim beam <[email protected]> wrote:
>>>>>> datakoll wrote:
>>>>>>> A PHOTO OF a correct spoke length as the spoke end sits in the
>>>>>>> mounted nipple. Notice the length is NOT at the ERD position.
>>>>>> then your problem has been confusion over what "erd" means. if
>>>>>> you use the rim manufacturer's erd data, and one of the spoke
>>>>>> calculators, the result will be perfect spoke length, as per
>>>>>> andrew's photo. every time.
>>>>>
>>>>> OK in that case I'm still confused about ERD means.
>>>>
>>>> "erd" is simple enough - it's what "effective" means that's unclear.
>>>> maybe that's why mavic call it "spoke support" - since they clearly
>>>> haven't read jobst's book and are untainted by its terminological
>>>> inexactitudes.
>>>
>>> Now I'm confused. I thought the ERD was measured from opposite nipple
>>> seats in the rim and was \exactly\

>>
>> "\" not "/"??? you've been playing with windoze _way_ too much my
>> friend.

>
> SUSE 10.3, but anyhow it's not a discussion about OS's.
>
>>> the number that determines spoke
>>> length, eliminating the tyre seat nipple support difference. Thus
>>> double wall, nipple seats et al, do not matter, the ERD is
>>> the figure you need to know for spoke lengths.

>>
>> "erd" is calculation input. you decide the result you want it to give.

>
> But the output is the spoke length, if I knew the spoke length I could
> calculate the ERD, but I don't know the spoke length, so which ERD do I
> choose?
>
> My point was, surely it's defined?


by the rim, yes!


> Actually, I'm ****** and I'm going
> to bed, thoroughly confused about whether a manufacturers ERD is to be
> trusted or is just a number they dreamed up.


this is a recurrent theme on r.b.t that i just don't understand!!! why
would anyone, ever, when given data by a manufacturer that has zero
influence on sales, especially when verified by a reliable r.b.t
contributor, ever get into issues of "trust" about that data??? i
simply can't comprehend that psychology.


>
> I'm going to be dreaming spokes :(
>
> <snip for brevity>


study this picture, courtesy of andrew muzi:

http://www.yellowjersey.org/photosfromthepast/SPOKDEPT.JPG

manufacturer numbers give you this result. your interpretation of that
information is up to you.
 
datakoll wrote:
> No Beam, the question is not does the math work out right, the
> question is are the MO people capable of using spoke calc. And why
> not?


unles you specify rim, hub and spoke crossing, the mo folks are simply
going to supply what you ask for. if you don't ask for the right length
because it's not calculated correctly, you'll not get the right product
delivered.



> The results of this survey, limited as it is to the usual group of
> cranks, screwballs, gyrogearloosi, and incompetents, head in the
> direction of how is the ERD described in English.
>
> The ERD is snot the spoke length. Spoke length is less than ERD. BUT!
> spoke length is continuously described as ERD. That's the impression I
> go away with.


it's simply calculation input, along with hub data and spoke crossing!!!
for any given erd, you'll get different spoke lengths for each of the
crossing options.


>
> If you thread the nipple onto the spoke you will see the nipple seated
> onto the rim at the (average) ERD has no more thread capacity.


no, average spoke length, not erd.

>
> That was the question I asked. Where is the spoke end minus the ERD?
> And the answer came back: The spoke end is the ERD. read it!


no, the erd /gives/ the spoke length when used in the calculation.


>
> Like the ship is going down on defining the ERD for computer entry
> data but then the ERD becomes the spoke length: forgetabboutit.
>
> Someone go thru 10 spoke calcs reading if the calcs say what the ERD
> is.
>
> what's the purpose? the question is: what's the purpose of approaching
> the ERD so closely like its a game of chicken (?!) getting the spoke
> end right on top the ERD reduces the spokes chances for adjustment as
> you just ran the spoke out of threads. So quack deduct 3mm from ERD.


you can. but rights to bleat about the result are thus automatically
forfeit.


>
> I'm inclined to get a spoke length that touches the inside eyelet.
> that's a good -3mm from ERD-and useful in my experience for HD touring
> and long mileage wheel use.
>


post your rim info, hub info and desired crossing count. we'll then
calculate spoke length and you can go ahead and do your mo.
 
Frank Leake writes:

> But the output is the spoke length, if I knew the spoke length I
> could calculate the ERD, but I don't know the spoke length, so which
> ERD do I choose?


> My point was, surely it's defined? Actually, I'm ****** and I'm
> going to bed, thoroughly confused about whether a manufacturers ERD
> is to be trusted or is just a number they dreamed up.


Try: http://www.damonrinard.com/SpocalcExpress.xls

You can change ERD and cross pattern until you find one that meets
your spoke length for your favorite spoke. The result is on the
screen as fast as you can hit ENTER. Try it, you'll like it. Of
course it solves for all the reasonable cross patterns at the same
time anyway.

Jobst Brandt
 
On Feb 2, 3:11 pm, Tosspot <[email protected]> wrote:
> jim beam wrote:
> > Tosspot wrote:
> >> jim beam wrote:
> >>> Ben C wrote:
> >>>> On 2008-02-02, jim beam <[email protected]> wrote:
> >>>>> datakoll wrote:
> >>>>>> A PHOTO OF a correct spoke length as the spoke end sits in the
> >>>>>> mounted nipple. Notice the length is NOT at the ERD position.
> >>>>> then your problem has been confusion over what "erd" means.  if
> >>>>> you use the rim manufacturer's erd data, and one of the spoke
> >>>>> calculators, the result will be perfect spoke length, as per
> >>>>> andrew's photo.  every time.

>
> >>>> OK in that case I'm still confused about ERD means.

>
> >>> "erd" is simple enough - it's what "effective" means that's unclear.
> >>>  maybe that's why mavic call it "spoke support" - since they clearly
> >>>  haven't read jobst's book and are untainted by its terminological
> >>> inexactitudes.

>
> >> Now I'm confused.  I thought the ERD was measured from opposite nipple
> >> seats in the rim and was \exactly\

>
> > "\" not "/"???  you've been playing with windoze _way_ too much my friend.

>
> SUSE 10.3, but anyhow it's not a discussion about OS's.
>
> >> the number that determines spoke
> >> length, eliminating the tyre seat nipple support difference.  Thus
> >> double wall, nipple seats et al, do not matter, the ERD is
> >> the figure you need to know for spoke lengths.

>
> > "erd" is calculation input.  you decide the result you want it to give..

>
> But the output is the spoke length, if I knew the spoke length I could
> calculate the ERD, but I don't know the spoke length, so which ERD do I
> choose?
>
> My point was, surely it's defined?  Actually, I'm ****** and I'm going
> to bed, thoroughly confused about whether a manufacturers ERD is to be
> trusted or is just a number they dreamed up.
>
> I'm going to be dreaming spokes :(


I check the ERDs for new model Mavic rims at several sites -- the
manufacturer, the usual on-line spoke calcs and in the groups just to
make sure. This is because I have gotten some wrong ERDs from the
Mavic site in years gone by. I trust the ERDs posted by Velocity, and
they have always yielded the right spoke lengths. Most of the spoke
calcs on line are pretty good and yield the same spoke length, but it
never hurts to use two or three of them just to cross check. -- Jay
Beattie.
 
On Feb 2, 7:24 pm, [email protected] wrote:
> Frank Leake writes:
> > But the output is the spoke length, if I knew the spoke length I
> > could calculate the ERD, but I don't know the spoke length, so which
> > ERD do I choose?
> > My point was, surely it's defined?  Actually, I'm ****** and I'm
> > going to bed, thoroughly confused about whether a manufacturers ERD
> > is to be trusted or is just a number they dreamed up.

>
> Try:  http://www.damonrinard.com/SpocalcExpress.xls
>
> You can change ERD and cross pattern until you find one that meets
> your spoke length for your favorite spoke.  The result is on the
> screen as fast as you can hit ENTER.  Try it, you'll like it.  Of
> course it solves for all the reasonable cross patterns at the same
> time anyway.
>
> Jobst Brandt


http://www.machinehead-software.co.uk/bike/spokes/spoke_pattern_explorer.html

also a possible software for figuring thru entering various known
quantities. I haven't tried it yet.

Jim Beam: the problem underlying the post question was an inexplicable
ongoing thickhgeadedness by MO software for supplying wrong spoke
lengths for double wall rims. A possible answer was the maybe ill
defined ERD application to real life non-LBS wheel building.

I was asking for where does the spoke end end in realtion to the rim
when the parts are on the dishing beam and built. I have a real
measure to the inside rim surface from hub hole and, have done this
before. BUTBUTBUT I wanted to refine the guesstimate. I have a vague
answre that vaguely agrees with my vague memory of before.

Practically tho, the nearness of LBS spoke ends spoken of here is
waaaayyyyy too close for my use. I'll go with ERD -3mm.
 
On Feb 2, 9:39 pm, datakoll <[email protected]> wrote:
> On Feb 2, 7:24 pm, [email protected] wrote:
>
>
>
>
>
> > Frank Leake writes:
> > > But the output is the spoke length, if I knew the spoke length I
> > > could calculate the ERD, but I don't know the spoke length, so which
> > > ERD do I choose?
> > > My point was, surely it's defined?  Actually, I'm ****** and I'm
> > > going to bed, thoroughly confused about whether a manufacturers ERD
> > > is to be trusted or is just a number they dreamed up.

>
> > Try:  http://www.damonrinard.com/SpocalcExpress.xls

>
> > You can change ERD and cross pattern until you find one that meets
> > your spoke length for your favorite spoke.  The result is on the
> > screen as fast as you can hit ENTER.  Try it, you'll like it.  Of
> > course it solves for all the reasonable cross patterns at the same
> > time anyway.

>
> > Jobst Brandt

>
> http://www.machinehead-software.co.uk/bike/spokes/spoke_pattern_explo...
>
> also a possible software for figuring thru entering various known
> quantities. I haven't tried it yet.
>
> Jim Beam: the problem underlying the post question was an inexplicable
> ongoing thickhgeadedness by MO software for supplying wrong spoke
> lengths for double wall rims. A possible answer was the maybe ill
> defined ERD application to real life non-LBS wheel building.
>
> I was asking for where does the spoke end end in realtion to the rim
> when the parts are on the dishing beam and built. I have a real
> measure to the inside rim surface from hub hole and, have done this
> before. BUTBUTBUT I wanted to refine the guesstimate. I have a vague
> answre that vaguely agrees with my vague memory of before.
>
> Practically tho, the nearness of LBS spoke ends spoken of here is
> waaaayyyyy too close for my use. I'll go with ERD -3mm.- Hide quoted text -
>
> - Show quoted text -


ach did that again JB! (ERD/2)-3mm=spoke length
 
On 2008-02-02, Tosspot <[email protected]> wrote:
> jim beam wrote:

[...]
>>>> "erd" is simple enough - it's what "effective" means that's unclear.
>>>> maybe that's why mavic call it "spoke support" - since they clearly
>>>> haven't read jobst's book and are untainted by its terminological
>>>> inexactitudes.

[...]
>> "erd" is calculation input. you decide the result you want it to give.

>
> But the output is the spoke length, if I knew the spoke length I could
> calculate the ERD, but I don't know the spoke length, so which ERD do I
> choose?


You decide what point in the rim cross-section you want the spoke ends
to reach. Then you measure the distance from there to the corresponding
opposite point on the other side. That's the ERD.

> My point was, surely it's defined?


It is defined, but in terms of what you personally want! This is what
Jim Beam is saying, also Damon Rinard on the link posted earlier.

http://sheldonbrown.com/rinard/spocalc.htm
"Effective Rim Diameter (ERD) is the diameter on which you want the
ends of the spokes to lie. Most people prefer it near the end of the
spoke nipple."

But, in Sheldon's glossary, a slightly different definition:

http://www.sheldonbrown.com/gloss_e-f.html
"Effective Rim Diameter. This is the rim diameter measured at the
nipple seats in the spoke holes, plus the thickness of the two
nipple heads. The E.R.D. is needed for calculating the correct
spoke length."

This second definition implies ERD is defined as distance between nipple
seats. But according to the first definition it's only that distance if
_that's how long you personally like your spokes_. Some people might add
3mm to that.

> Actually, I'm ****** and I'm going to bed, thoroughly confused about
> whether a manufacturers ERD is to be trusted or is just a number they
> dreamed up.


It would be much better if manufacturers always just quoted spoke
support diameter. Then you know what the number actually is supposed to
correspond to and can add 3mm if you like longer spokes, or not if you
don't.

If 3mm ended up getting added twice due to these misunderstandings the
spokes could be too long by enough to cause a real problem.
 
jim beam wrote:
> Tosspot wrote:
>> jim beam wrote:
>>> Tosspot wrote:
>>>> jim beam wrote:
>>>>> Ben C wrote:
>>>>>> On 2008-02-02, jim beam <[email protected]> wrote:
>>>>>>
>>>>>>> datakoll wrote:
>>>>>>>> A PHOTO OF a correct spoke length as the spoke end sits
>>>>>>>> in the mounted nipple. Notice the length is NOT at the
>>>>>>>> ERD position.
>>>>>>> then your problem has been confusion over what "erd"
>>>>>>> means. if you use the rim manufacturer's erd data, and
>>>>>>> one of the spoke calculators, the result will be perfect
>>>>>>> spoke length, as per andrew's photo. every time.
>>>>>>
>>>>>> OK in that case I'm still confused about ERD means.
>>>>>
>>>>> "erd" is simple enough - it's what "effective" means that's
>>>>> unclear. maybe that's why mavic call it "spoke support" -
>>>>> since they clearly haven't read jobst's book and are
>>>>> untainted by its terminological inexactitudes.
>>>>
>>>> Now I'm confused. I thought the ERD was measured from opposite
>>>> nipple seats in the rim and was \exactly\
>>>
>>> "\" not "/"??? you've been playing with windoze _way_ too much
>>> my friend.

>>
>> SUSE 10.3, but anyhow it's not a discussion about OS's.
>>
>>>> the number that determines spoke length, eliminating the tyre
>>>> seat nipple support difference. Thus double wall, nipple seats
>>>> et al, do not matter, the ERD is the figure you need to know
>>>> for spoke lengths.
>>>
>>> "erd" is calculation input. you decide the result you want it to
>>> give.

>>
>> But the output is the spoke length, if I knew the spoke length I
>> could calculate the ERD, but I don't know the spoke length, so
>> which ERD do I choose?
>>
>> My point was, surely it's defined?

>
> by the rim, yes!
>
>> Actually, I'm ****** and I'm going to bed, thoroughly confused
>> about whether a manufacturers ERD is to be trusted or is just a
>> number they dreamed up.

>
> this is a recurrent theme on r.b.t that i just don't understand!!!
> why would anyone, ever, when given data by a manufacturer that has
> zero influence on sales, especially when verified by a reliable r.b.t
> contributor, ever get into issues of "trust" about that data??? i
> simply can't comprehend that psychology.
>
>> I'm going to be dreaming spokes :(
>>
>> <snip for brevity>

>
> study this picture, courtesy of andrew muzi:
>
> http://www.yellowjersey.org/photosfromthepast/SPOKDEPT.JPG
>
> manufacturer numbers give you this result. your interpretation of
> that information is up to you.


Ah, I see the argument now. Right, I shall retire and watch the rest of
the thread.
 
On 2008-02-03, datakoll <[email protected]> wrote:
> On Feb 2, 9:39 pm, datakoll <[email protected]> wrote:

[...]
> ach did that again JB! (ERD/2)-3mm=spoke length


Of course not! To work out spoke length from ERD you need to know hub
dimensions and number of crossings and do the proper formula, which is
more complicated than that one.

The question is what's your manufacturer quoting. If it's Mavic, they
quote spoke support diameter, so just use that. Don't subtract 3mm.

If it's someone else and they quote "ERD" you have a problem because who
knows whether they added a bit to the spoke support diameter to get ERD
or not. It depends on their personal preference.

Best advice is just go with what the rim manufacturer quotes. If they
think you need spokes a little bit longer than you do just live with it.
If you add/subtract 3mm trying to second-guess what they mean by ERD you
risk doubling the error.