Have a look at my new spoke length calculator web app!

Ah, might be the 'Campag low track' instead actually

Very helpful and loads more user friendly than the original spreadsheet!

I recently did my first wheel build and ended up with spokes that were too long based upon the spoke calc results. Rims like the Rigida DP18 have a clause in brackets that says (ERD is Rigidas Nipple seat dia plus 3mm for nipples).

The spoke calc gave me 281.1mm so i rounded this down to 280mm and they were too long (couldn't get the tension right). In the case of a rim like the DP18 should this 3mm be subtracted from the final result - i swapped my 280mm out for 278mm's and its perfect which fits with the original result of 281-3=278mm?

I suppose my question would be should/could this subrtraction of 3mm be taken into account in the final result?

What hubs did you use? I built a wheel with Goldtec hubs and DP18s and the length was just right.

I emailed Damon Rinard, the author of the original spreadsheet, and asked about the thing in brackets. He emailed me the following:

For wheel building, there are two important (and often confused) rim diameters: ERD, effecive rim diameter, and NSD, nipple seat diameter.

ERD is the diameter through the ends of ideal-length spokes. It's measured on the theoretical spoke end, not on the rim.

NSD, nipple seat diameter, is the diameter of the circle through all the nipple seats. It's measured on the rim.

Typically, with normal nipples the spoke extends radially outward a little bit beyond the nipple seat, and into the spoke head.

Spocalc calcualtes spoke length and wants the diameter of the ends of ideal spokes, so NSD isn't the dimension spocalc uses.

The comment in the database means I've added 3 mm to Mavic's nipple seat diameter to approximate typical (DTSwiss 14 mm) nipples. So for that rim there might be some adjustment needed if using other nipples.

hope this helps,

Damon Rinard

I still wonder though why he added the 3mm to some but not all rims though.

I used an on-one hub which is in the database, plus i also measured with Verniers to double check? Could have been to do with the nipples i used, although they are just standard "short" nipples that came with the spokes?

I still wonder though why he added the 3mm to some but not all rims though.

Maybe because in most cases ERD is the given figure (either from the manufacturer or obtained by measurement), but for some rims the manufacturer states their NSD, so ERD has to be calculated from it?

As long as you are putting an ERD into the calculation, you should be getting spoke lengths out. To check that you are putting ERD in, compare the value used by edd with data from the manufacturer if you can find it - if they say it's an NSD, it should be 3mm (ish) smaller than the ERD. The 'ish' might depend slightly on how the nipple sits in the rim's eyes, and significantly on how far the nipple's thread extends towards the hub.

The basic spoke length calculation just works out the straight-line distance from the edge of the hub hole to where the spoke should end. This doesn't allow for the extra length taken up weaving the last cross, or the length gained from spokes stretching as they are tensioned. The weaving effect should be negligible (less than 0.01mm) unless you are weaving some weird pattern, but i'd expect spokes to stretch 0.4 to 0.6mm when tensioned. i.e. just on the bounds of consideration, but not enough to explain what went wrong above.

I used an on-one hub which is in the database, plus i also measured with Verniers to double check?

Did you measure your rim's ERD to check too - it's possible they vary a bit as the dies they are extruded from wear out & are then replaced.

Could have been to do with the nipples i used, although they are just standard "short" nipples that came with the spokes?

I think spokecalc & edd's calculations assume normal short 12mm nipples, so probably not.

I must admit no i didn't check the ERD of the rim manually, it was no big deal as i knew i could sort it by getting some 2mm shorter spokes. No biggie but just a tad confusing when its your first build, other than that it all went swimmingly.

As for the nipples yeah they were 12mm so that shouldnt have had any effect.

Tremendous job mate

Hi
I'm trying to calculate the lenghts for mavic cxp22 but there's only cxp22s or cxp22n. Which one shall i use?

Found the answer on Arup's blog:) miche large flange on cxp22 3cross = 290mm

Just wondering, you have got the Dia Compe Gran Compe Rear Hub on the list but not the front. Are the dimensions the same. I only ask as I have a rear along with a Deep V rim, and am ordering a box of DT swiss spokes so when I have more money, then I can buy a front rim and hub!

Also, it says for a 32 hole, 3 cross set-up I would need 281.1 spokes. Do you recon that 280's would be fine for the job?

Great application btw. Thanks a lot dude!

You're right in the middle, but yes 280 is fine.

The on one shop says front and rear have the same measurements: http://www.on-one.co.uk/i/q/HUDC32F/dia-compe-gran-compe-front-hub

Obviously you'd have to take their word for it. Doesn't sound unreasonable though.

I'm trying to calculate the length for mavic cxp22 + gran compe hubs.*
The measurements for the hub are already in Ed's calculator. I'm entering 599mm as a rim diameter which i hope is correct. The spoke length for a 3 cross comes up as 289.5 for both wheels and i'll be buying 289mm spokes.
If the front hub is 100mm shouldn't the measurement be different and spokes slightly shorter?
Thanks

Looks to me like those front and rear hubs have exactly the same flange diameter (62mm) and offset (32mm each way) measurements. The over-locknut dimensions of the hubs (100m front and 120mm rear) are irrelevant to choosing spokes, it just means that the rear has its locknuts 10mm further from the flanges, i.e. about the width of the cog and lockring threading.

Ok, just needed to be sure,
I know, silly question.
thanks

I just ordered 289mm dt swiss spokes in box of 100 for 27.99 from fatbirds.
My hubs arrived today and front and rear are not the same. I just trusted planet x website which was showing 32 c-f for both hubs.
The front one is actually 34mm c-f.
The spoke calc gives me now 289.5 for rear and 289.8 for the front wheel.

Can i get away with 289mm for both wheels?*
Or should i change my order (i think it hasn't been dispatched yet) for 290mm spokes.
Or cancel it and get the spokes in different lengths for front and rear wheel?

niceee

I'm sure you'll be fine. I used this app for my calculations, but when the wheel-builder put together my wheels he reckoned the spoke lengths were a few mm out - the point is that this made no difference whatsoever to the build, or the strength of the wheels. Your difference is even less so won't matter at all.

ok, thanks:)

Yeah jsurt built my rear. Velocity Deep V, Gran Compe and Halo Duble Butted (280's though the calc read 281.1). Came out great. thanks for the calculator...

great facility,worked out on two pairs of wheels,ta

nice

Have a bump. Just used this again with success.

So it was a little over 4 years since I have launched the app and I've received a steady stream of hub and rim submissions over the years thanks to the users of the app.

The page was starting to look a little dated and I was getting a little embarrassed of it so ... I've redesigned the thing: http://lenni.info/edd/

Not only does it no longer look hideous but I've also cleaned up the codebase enormously. It's amazing what you learn in a few years of making software.

I have a favour to ask of you: If you notice a problem when using the app, would you be able to send me feedback either here, on the comment boxes on the site or email to leonard.ehrenfried@gmail.com?

Thanks a lot!

Nice, looks good.
I think 28 spokes is quite common in comparison with 16 and 18