How to measure exactly the length of a single spoke?

Hi,
I have an old used set of Sapim Laser spokes here, bought as '291mm'.
For a new wheelbuild, Lenni/EDD says I need 292.8mm spokes.

Now I am wondering if those Sapim spokes are actually 292mm long in reality and would fit to the new build, but it completely depends on the exact way the spokes are measured.

Therefore: WHICH way is the correct way (i.e. the way Lenni/EDD is based on?)

There are 3 different ways to measure: always from end of thread, until A/ Centre of spoke head, B/ under large part of spoke head or C/ under small part of spoke head

A/ (see 'bicycle spoke'):

http://www.myronsmopeds.com/wp-content/uploads/2011/09/Spokes7.jpg

OR B/

https://lh3.googleusercontent.com/-4FVlXF8W92k/TX5RfFswwWI/AAAAAAAAANo/rNQetzKl9Gg/Spoke%2BLength.jpg

OR C/ (see 'L')

http://www.wws-speichen.de/wp-content/gallery/sortiment/3.gif

a mm or two doesn't really matter when dealing with spokes there is a bit of lee way in the nipple which will allow for whatever method you use to measure the length
the difference between the above three options really won't be that big

not the answer you were looking for ... sorry... but it's what i have been told

If it's A, then my spokes will actually be 292 and fit, if they are B/C, then they are more like 291mm and I guess that's not enough if EDD says I need ~293?

No?

It would be good to hear what Lenni says about this, what his calculator is based on. Isn't he a forumenger?

My spoke ruler gives you a spoke length that's based on C above (L in the diagrams you link to).

As Dicki says, a mm or two rarely makes much odds, and different calculators often give slightly different results. I'd run it through another calculator (I normally use Spocalc - search for Damon Rinard spocalc.xls and you'll find it), and see what that says - if it comes out as 292 or 293mm, just try building the wheel anyway, and it'll almost certainly work. If it comes out as (say) 295mm, I'd probably give it a go in any case, but without expecting it to work well.

EDD is based on spocalc.xls, i.e. it gives the same result (292.8)

As jsabine says a DT Swiss spoke ruler has the spoke hanging from the spoke head through a hole in the ruler with the MM starting from edge of the hole.

You can do the same hanging it off a steel ruler that starts from zero.

^ ok - what would you do in my case? buy a new set of 293mm spokes, or go with the 291mm's?

Hi jetski,

(I'm Lenni, you send me an email today). I think adoubletap is correct. You should measure from the the end of the spoke until the "elbow", basically where the spoke starts to bend or put another way where the hole in the hub starts.

In your case I would go with the spokes you have.

ok, then it's clearly C/

my spokes are exactly 291mm with this method.

are you sure I should use them? now it's clear there are ~2mm missing according to spocalc.

Longer nipples? 12 and 14mm are both common sizes.

go longer rather than shorter. i.e. if you need 292.8 get 294.

Longer nipples have the same threaded length as short ones so won't help. Just go for it with the spokes you have.

And better to be a fraction shorter than longer, otherwise you can get the end of the spoke protruding from the nipple. This doesn't matter normally if you have a box section rim, but will cause punctures if it's protruding into the tyre well.

that's why we use rim tape

I've seen a spoke end go through rimtape.

Surprised that you could get a spoke to have enough thread to go that deep. Usually they will bottom out before getting to that point.

Longer nipples have the same threaded length as short ones so won't help. Just go for it with the spokes you have.

I don't get that. Wouldn't 14mm nipples instead of 12mm's compensate exactly for the two missing millimeters?

12 mm nipples have 4 mm of unthreaded hole, 7 mm of thread up to the bottom of the slot and 1 mm more to the top of the slot. Spokes usually have 9.5 to 10 mm of thread.

Longer nipples are primarily for deep section rims that short nipples wouldn't stick far enough out of to turn with a spoke key. Depending on brand some have just the same length of thread inside, and some gain 1mm of thread for every 2mm extra length.

So they will leave less spoke thread visible, but they may not increase the length of thread to thread engagement.

In your case, 12mm nipples would leave you 5mm of thread engagement and spoke threads just covered. I think 5mm is enough to resist pull-out, but having the spoke not reach up to the bottom of the slot increases the chance the nipple will snap. The only way to fix that is longer spokes.

If you have 12 mm sapim polyax to hand, i'd say use them. If you're buying new nipples anyway get DT swiss 14 mm for an extra 1 mm of thread engagement.

I do have 12mm sapim polyax, yes.

How about 14mm sapim polyax, do they let me gain some extra mm as well?

as far as i know, sapim are one of the brands where longer nipples don't have longer threads, though on another thread recently someone claimed that some new sapim nipples are different.

(it's a trade off - sapim's approach is less accommodating of having the wrong spoke length, but is arguably stronger because you can get the spoke all the way to the slot even on rims where you need long nipples to be able to turn them.)

Just build the bloody thing with the bits you've got.

If it doesn't work, ask here what new bits you need to make it work.

If you take it steady,I'd be amazed if you have problems.

Use a ruler.