Oh wise ones: Spoke lengths

Hello,

For my rim/hub combination (Shimano NX-30 dynamo and Mavic Open Pro),
Spocalc.xls seems to think that spokes of length 284.7 would be best.
Obviously spokes of this exact length aren't available.

My question is, should I buy 284 or 285 spokes? Nothing I've seen in the
Bicycle Wheel or online seems to indicate that either length is better than
the other as 1mm difference from the ideal length each way seems to be
entirely acceptable, however I may have misunderstood or missed something.

Intuition tells me that 285 would be the best length, intuition is not
always the best counsel of course!

Any advice appreciated[1].

Regards,

-david

[1] Even "stop obsessing over details and get building"...

David Nutter wrote:
For my rim/hub combination (Shimano NX-30 dynamo and Mavic Open Pro),
Spocalc.xls seems to think that spokes of length 284.7 would be best.
Obviously spokes of this exact length aren't available.

My question is, should I buy 284 or 285 spokes?

285 - round to the nearest mm. Those few tenths will be the least of your
worries. I hate to worry you but spoke calculators can sometimes be
incorrect by more than one whole mm. Best to use more than one calculator
to check (although the DT online one doesn't seem to include your hub).

By the way I'd really appreciate some numbers the wheels listed below to
compare to DT's - if it's not too much trouble for someone to help. I
can't get the full spocalc.xls to download and work on my computer:

Front wheel #1:
Campag Chorus 2001 (new style 9/10sp) 32h
Mavic Open Pro 700c
3x

Rear wheel #1:
Campag Chorus 2001 (new style 9/10sp) *36h*
Mavic Open Pro 700c
3x right, 2x left

Front and rear wheels #2:
Campag Mirage 8-speed 1999 36h
Mavic MA2 700c
3x

Rear wheel #3:
Shimano Nexus 7 36h
Vuelta Tempest 700c
3x

cheers
~PB

Advice from DT:
"Generally it is worth: When thinner spokes are used, the more the
calculated spoke length can be rounded down and vice-versa!!!"
www.dtswiss.com/index.asp?fuseaction=spokes.bike - Spoke
Calculator

~PB

Pete Biggs said:
David Nutter wrote:
For my rim/hub combination (Shimano NX-30 dynamo and Mavic Open Pro),
Spocalc.xls seems to think that spokes of length 284.7 would be best.
Obviously spokes of this exact length aren't available.

My question is, should I buy 284 or 285 spokes?

285 - round to the nearest mm. Those few tenths will be the least of your
worries. I hate to worry you but spoke calculators can sometimes be
incorrect by more than one whole mm. Best to use more than one calculator
to check (although the DT online one doesn't seem to include your hub).

Argh, nothing is ever simple

By putting the same hub numbers as Spocalc into the DT calculator, I get
283.3. The difference seems to be that DT thinks the Open Pro is 602mm in
diameter while Spocalc thinks it is 605mm. By tweaking the rim diameter
number, I get 284.7 again indicating the same equations are used at least

By the way I'd really appreciate some numbers the wheels listed below to
compare to DT's - if it's not too much trouble for someone to help. I
can't get the full spocalc.xls to download and work on my computer:

I've converted the Hub and Rim datasheets from Spocalc into PDF if that's
useful for you.

You can get them he

http://www.dur.ac.uk/david.nutter/spocalc-hubs.pdf and
http://www.dur.ac.uk/david.nutter/spocalc-rims.pdf

Perhaps the Spocalc spreadsheet without the rim and hub dbs will work for
you? If not I'll do the calculations for you this evening, if nobody else
obliges first.

Regards,

-david

David Nutter wrote:
By putting the same hub numbers as Spocalc into the DT calculator, I
get 283.3. The difference seems to be that DT thinks the Open Pro is
602mm in diameter while Spocalc thinks it is 605mm. By tweaking the
rim diameter number, I get 284.7 again indicating the same equations
are used at least

DT have some special notes about Mavic rims in the "instructions"
(something about Mavic's errors and offset holes, etc) but I must admit
that they're as clear as mud to me.

I've converted the Hub and Rim datasheets from Spocalc into PDF if
that's useful for you.

You can get them he

http://www.dur.ac.uk/david.nutter/spocalc-hubs.pdf and
http://www.dur.ac.uk/david.nutter/spocalc-rims.pdf

Thank you very much! I'll have a go with those tonight or tomorrow.

Perhaps the Spocalc spreadsheet without the rim and hub dbs will work
for you?

Probably will but I'm not sure. I should be able to use the numbers one
way or another.

If not I'll do the calculations for you this evening, if
nobody else obliges first.

Cheers!

~PB

On Mon, 17 Nov 2003 11:42:42 +0000 (UTC), David Nutter
wrote:

Hello,

For my rim/hub combination (Shimano NX-30 dynamo and Mavic Open Pro),
Spocalc.xls seems to think that spokes of length 284.7 would be best.
Obviously spokes of this exact length aren't available.

My question is, should I buy 284 or 285 spokes? Nothing I've seen in the
Bicycle Wheel or online seems to indicate that either length is better than
the other as 1mm difference from the ideal length each way seems to be
entirely acceptable, however I may have misunderstood or missed something.

Intuition tells me that 285 would be the best length, intuition is not
always the best counsel of course!

Any advice appreciated[1].

Not exactly scientific, but I always [well on the 6 occasions I've
built wheels] round down, mainly because there's less chance of the
spokes poking through the nipple and into the rim tape [although this
obviously depends on the style of your rim I guess...mine are basic!],
and also if the spoke is too long there might be a chance that all the
threads on the spoke may not grip the threads of the nipple...
although the reverse of this is also true if threads are visible on
the spoke after you've finished building the wheel!!
Bet it doesn't really matter 'that' much at the end of the day.

Garry

Garry Broad wrote:
............
although the reverse of this is also true if threads are visible on
the spoke after you've finished building the wheel!!

One trick to get round that is to use 16mm nipples instead of 12mm as they
have 2mm more thread. I checked, with new DT nipps, after Jobst Brandt
said it wasn't true! :-)

Bet it doesn't really matter 'that' much at the end of the day.

It doesn't (you can get away with one or two mm out quite easily) - except
when you've chosen the wrong lengths in the first place, so that final
millimetre can make the difference between the spokes being useable or
not.

~PB

Pete Biggs said:

Your numbers:

Front wheel #1:
Campag Chorus 2001 (new style 9/10sp) 32h
Mavic Open Pro 700c
3x

Spocalc says: 296.5 for a three-cross.

I used the following hub entry:

2.4 39.0 35.4 39.0 35.4 F 100 Campagnolo Chorus, Daytona OS 2002 Mar 01 www.campagnolo.com

Rear wheel #1:
Campag Chorus 2001 (new style 9/10sp) *36h*
Mavic Open Pro 700c
3x right, 2x left

I think you're on your own with this one! Spocalc won't let me specify
different crossings for drive/non-drive spokes.

Front and rear wheels #2:
Campag Mirage 8-speed 1999 36h
Mavic MA2 700c
3x


IN both cases I'm using the appropriate entries titled

"Campagnolo 1999+ Athena, Veloce, Mirage".

Note that Spocalc thinks the rear hub is 9spd.

For the front:

298.0

For the rear:

297.2 on the left.
295.4 on the right.


Rear wheel #3:
Shimano Nexus 7 36h
Vuelta Tempest 700c
3x

Unfortunately spocalc has no dimensions for the Tempest rim.

Hope this is useful.

Regards,

-david

David Nutter wrote:
/snip
Rear wheel #1:
Campag Chorus 2001 (new style 9/10sp) *36h*
Mavic Open Pro 700c
3x right, 2x left

I think you're on your own with this one! Spocalc won't let me specify
different crossings for drive/non-drive spokes.

Nevermind, I'll use DT's calculator and Spocalc's database numbers.

Front and rear wheels #2:
Campag Mirage 8-speed 1999 36h
Mavic MA2 700c
3x

IN both cases I'm using the appropriate entries titled

"Campagnolo 1999+ Athena, Veloce, Mirage".

Note that Spocalc thinks the rear hub is 9spd.

Not the right one then (dishing will be different). Maybe my hub is '98
or Avanti (probably Avanti anyway but I was assuming Mirage was the
same.).

/snip
Hope this is useful.

It is. Many thanks!

~PB

David Nutter wrote:
Rear wheel #1:
Campag Chorus 2001 (new style 9/10sp) *36h*
Mavic Open Pro 700c
3x right, 2x left

I think you're on your own with this one! Spocalc won't let me specify
different crossings for drive/non-drive spokes.

The usual way to get around that is to run the numbers twice as if it was
two wheels: one all 2x and one all 3x then just take the appropriate
results from each side. But please don't bother doing that for me as it's
not urgently required.

cheers
~PB