Spoke length? Which site to agree with?

Hi guys,

First time wheel builder.  I’ve plugged all the numbers into Sapin, Edds, an another one.

Got 290/286, 287/285 and 291/289 measurements.

What do I go for?

Thanks

Chris

even numbers only anyway IIRC. split the difference if you have to. you don’t need to overthink it.

Thanks Del.  Do you think 286 and 288 will be ok then?  It’s for an ambitious 24h 2xCross so perhaps shorter is better for tension?

I had this with my last set of wheels I was trying to build. I rang cycle basket and the guy there worked out the length for me and then I bought the spokes from them online. 45 per spoke (with nipple) for black double butted spokes and they arrived the next day.

Try DT Swiss if you want to double check. Never let me down.

download spocalc from Sheldon website. it what i use for all spoke length calculation (thousands of wheels) and it has never been wrong unless i input the wrong data.

those lengths are so different i would check your input info. Also if you are selecting rims and relying on the calculator knowing the correct ERD then stop. input the info yourself to ensure the same data is being used.

I wouldn’t trust any of those measurements as they are all so different!

I’ve used the Prowheelbuilder site for years and probably 100’s of wheels by now and no issues. But I’d be checking measurements first.

I like DT Swiss’s one, ironically it totally ****ed me the one time I built a wheel entirely with DT products- the automatic calculations for the fatbike rim doesn’t include the offset. But every time i’ve used it for anyone else’s products it’s been great.

Thing is, the basic distance between the centre of the flange hole and the circle defined by the ERD (tic offset) is a matter of simple trigonometry.  You then need to correct for stuff like the flange hole diameter, spoke diameter at the flange end and how much you want the spoke to protrude outside the ERD.  And finally deduct a bit for stretch and bedding in.  Calculators may differ in those corrections, for example some assume that ERD is measured to the face of the spoke bed and add a bit to account for the fact that the nipple head protrudes above it and so add a bit for that (they normally say that).  If you measured ERD yourself that correction may be built in to the way you measured it.  With no correction for stretch etc., spokes do end up a bit long if you had to round up to the closest 2mm size, so I tend to round down unless it is really close.  I recently built some 29er wheels with DT Revs and some spokes still poked above the nipple head a bit using this method, but not enough to cause a problem.

ETA spokes laced on the inside of the flange generally protrude a bit more than the other sort.

I have always used Edd and it has always been correct.  I do enter all the dimensions myself though (mainly because the components I use are not listed anyway)

Thanks all. Appreciate the advice. Off to measure!

Something wrong there, you have a 4mm difference between calculators.

When I have run 3 different calculators on the same wheel out of curiosity they all came back with the same spoke lengths (or a rounded version of the same length).

Sapim calculator uses inner rim diameter and you input rim thickness, most other calculators use ERD, easy to check yourself with 2 spokes/nipples and something to measure between.

Yep good to measure. As others have said there is something fishy about the disparity you observe.  I use Edd and Prowheelbuilder.com.  Using these sites my naive measurements with a cheap caliper seem to be fine.  I use the ERD provided by the rim manufacturer though.

I also round down the final length.

As an alternative to cycle basket there’s also totalcycling.com if cost is an issue. Black ACI Alpina F1 at 36p.  Limited range of sizes online but I found the chap helpful on the phone.  On the other hand,  <span style=”font-size: 0.8rem;”>I’ve never built a 24h wheel but would probably go for something more expensive.</span>

I aways get the same lengths with different calculators too.

I think you’ve got something wrong somwhere. Numbers in the wrong boxes? Did you remember to click 3 cross?

Yep, i reckon I must have balls’d up the numbers.

Will check again later when home. Although the prospect of building a 2xcross 24h as my first build is somewhat daunting as I’ve heard it’s very hard to get it right!

It can’t be that hard, I just built one. Lower spoke count and less stiff rims should in theory be harder to build with but I always found it makes it much easier to see the changes you’re making and to understand what’s going on. It’s probably easier to totally **** it up but I think it’s also easier to get it right. I mean, really right, not “sort of right but actually fairly badly wrong just in compensating ways so it’s still round” like you can do with burlier parts.