Spoke length for extralite to light-bicycle wide carbon 29er

Discuss light weight issues concerning mountain bikes & parts.

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Nicholas68
Posts: 69
Joined: Wed Jun 19, 2013 1:30 am

by Nicholas68

Hey guys.

Light bicycles only list the ERD of their wide carbon 29er rims. And extralite has the predetermined spoke lengths but you need to know the spoke end diameter and after many e-mails light-bicycles is struggling to understand what measurement I want. So in the hopes of building up my bike 2 weeks earlier and not having to wait for the rims to come in, measure them then order the rest of the parts I am hoping someone has done this combo before and remembers the spoke length or has some light-bicycle wide 29er carbon rims lying around and can perform the measurement for me.

Thanks Nic.

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dwaharvey
Posts: 493
Joined: Thu Oct 26, 2006 8:54 pm
Location: USA

by dwaharvey

From sheldon brown:

E.R.D.
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.

Not quite sure what you (or Extralite) mean by "spoke end diameter", but it sounds like the same thing as the ERD as defined above (since the spoke end is ideally flush with the top of the nipple).

Nicholas68
Posts: 69
Joined: Wed Jun 19, 2013 1:30 am

by Nicholas68

That's what I would have thought as well. But the guys at Extralite are saying ERD it's not an accurate way to measure. And they don't list the hub specs for a traditional spoke calculator. They have a chart with all the spoke lengths needed based on the spoke end diameter.

This is how they determine it.

http://www.extralite.com/Products/measu ... %20SED.htm

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ms6073
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Joined: Fri Jul 23, 2004 8:24 pm
Location: Houston, Texas

by ms6073

Nicholas68 wrote:They have a chart with all the spoke lengths needed based on the spoke end diameter.

This is how they determine it. http://www.extralite.com/Products/measu ... %20SED.htm" onclick="window.open(this.href);return false;

Seems to me Extralite is calling into question the accuracy of the E.R.D. measurement because what I see described in the link above is synonymous with Sheldon Brown's definition of E.R.D. I am guessing that because they spec high tension for wheel builds with the hubs, Extralite wants hyper accurate ERD but since typically spokes are supplied in 1mm length increments, teh difference is not going to matter unless you have a Hozan spoke cutting tool or similar. I would suggest you use the LB supplied ERD and get the hub tech specs and use the DT Swiss spoke calculator which should give you accurate spoke lengths.
Michael - The Anaerobic Threshold is neither...

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dwaharvey
Posts: 493
Joined: Thu Oct 26, 2006 8:54 pm
Location: USA

by dwaharvey

Agree with MS6073 that the number they are seeking is just a measured ERD. I guess they don't trust rim makers to publish an accurate number. I think you are making a mountain out of a mole hill here though. Personally I'd just use the LB ERD number and forget about it. If its a hub for j-bend spokes I'd google for the measurements of the hub and use a spoke length calculator myself; if not I'd go with the Extralite table. DT sell Aerolites in the US in even lengths so that's a testimony that they don't think getting spoke length more accurate than +/-1mm is necessary.

battler
Posts: 9
Joined: Fri May 23, 2014 2:04 pm

by battler

ive currently got the same dilemma. how did you go with this? was the ERD accurate?

scale29
Posts: 39
Joined: Sat Jun 04, 2011 5:40 pm

by scale29

If it helps in anyway I have just built up a pair of the wide 29 rims which had a measured ERD of 604mm v manufacturers 603mm

the hookless 29ers i also build had ERD of 594mm v manufacturers measurement of 592mm

battler
Posts: 9
Joined: Fri May 23, 2014 2:04 pm

by battler

i also measured 2mm on top of what LB claimed, but someone was holding the spokes with nipples screwed in (same effect as the rubber band trick which i just couldnt do), and the measuring tape was going over their fingers so i attributed that to adding the 2mm

i was thinking of going with their measurement. hmmm.

if it is 1 or 2mm longer than it would ideally be, i dont mind if the spoke protrudes through the end of the nipple as ill be running tubeless anyway but i worry about there being less holding onto the threading so more chance of them coming loose.

my first wheel build you see, paranoid about everything and i know nothing. gotta start somewhere!

i also dont like the extralite 'tables' they use to calculate spoke length. it's not accurate, and combined with the lack of confidence i have in LB measurements (and my own measuring) i'm worried it will be out by 2 or more mm.

the wheelpro.co.uk length calculator is what bikehubstore recommend and it looks simple enough. im going to email asking their opinion and maybe post that here as well.

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