Building wheel - working out spoke length

[Jezston]

On Saturday I shall be building my first wheel! It's a single speed coaster brake hub within a 26" mountain bike wheel in my attempt to make the ultimate pub bike.

However, I have hit a snag.

I was recommended to use Spocalc which apparently has near every rim and hub in existence and all I need to do is tell it which rim and hub i'm using and it'll tell me what spoke length to use. Except that neither my rim and hub are listed, in fact no products by either manufacturer are listed at all. Probably because they are generic toss, although this was kind of the point of the build.

It seems to work it out myself I need some REALLY precise measurement, down to 1/10th of a millimeter, which I just don't feel confident doing.

Anyone have any tips?

The rim is a Van Schothorst 26" MTB rim (no model name I'm afraid), and the hub is a Ventura single speed coaster hub (this one in fact).

 

[Night Train]

This seems to allow you to put in the measurements to calculate spoke length. (Edit: Seems to only calculate for radial spokes.)
Is Sheldon Brown any help?

Otherwise you can try contacting Spandex, of this forum, with the dimensions and maybe he can work out the spoke length and sell you the spokes at the same time. http://www.yourspokes.co.uk/
I get my wheel components and spokes from him and also build my own wheels.


I did do a 'trial and error' to spoke a hub gear into my winter hack using spokes removed from other wheels I had been stripping. It was time consuming and I had to rebuild the wheel three times before I found the 'Goldilocks' spoke set that was just right and not too long or too short to get three a cross pattern.
Not a recommended method though.

 

[amaferanga]

You don't need to measure anything down to 1/10 of a mm. Measure hub and rim to the nearest mm using one of the many guides on the internet and then use one of the spoke calcs with manual entry.

 

[RecordAceFromNew]

It seems to work it out myself I need some REALLY precise measurement, down to 1/10th of a millimeter, which I just don't feel confident doing.

Someone is pulling your leg.

The accuracy of the hub's lateral dimensions has little consequence on spoke length because of triangulation. Hub diameters are easy to measure accurately with a vernier. Regarding ERD, since +/- 1mm is ok at the nipple, that means +/- 2mm is ok with ERD, but much better should be achieveable with the right nipples, method and care. After all, where do you get spoke length correct down to 1/10 of a mm?

Van Schothorst is now Rigida.

 

[Mark Grant]

Here is an online spoke calculator. Been accurate the few times I've used it.

 

[PpPete]

Help tab on this page is good.
Or for a printed version this.

 

[PpPete]

This seems to allow you to put in the measurements to calculate spoke length. (Edit: Seems to only calculate for radial spokes.)

When you put the dimensions in it gives lengths for Radial, 1X, 2X, 3X, 4X

Also good are
http://www.kstoerz.com/freespoke/
http://lenni.info/edd/
and the one on the DT Swiss site (under Support)

 

[Night Train]

When you put the dimensions in it gives lengths for Radial, 1X, 2X, 3X, 4X

Ahhh, I didn't see that. Dodgy internet maybe as not everything appears on my screen sometimes.

 

[bobg]

Can't resist recommending Roger Mussons online book. "The Professional Guide to Wheelbuilding" It covers all this in detail but not in a complicated way. Only about £10 for a download and you can even e mail him with questions!! Best bike related £10 I ever spent.