Morning All,

As per title, is there an infallible way of calculating spoke length?

I have a number of wheel building related projects that I’m looking at, but the most pressing is a rim and spoke replacement (a complete rebuild really) of my Alfine 8 speed rear wheel.

I’m looking to use a Sun Ringle Inferno 27 rim- ERD is 601.

I’m struggling a little to find dimensions for the hub but what I have found is as follows:

OLN 135 mm
Spoke Hole Diameter 2.9 mm
Left Flange Diameter 92.8 mm
Right Flange Diameter 93 mm
Left Flange Offset 30.9 mm
Right Flange Offset 23.6 mm

According to http://www.prowheelbuilder.com I get:

Left spoke length: 288.3
Right spoke length: 289.3

With the same information on the http://www.sapim.be site I get the following:

With 1mm rim thickness,

Spoke length non-gear side: 289
Spoke length gear side: 290

With 1mm rim thickness,

Spoke length non-gear side: 290

Spoke length gear side: 291

So, what length spokes do I need?

Would 290 be OK for both sides?

Do I need to add anything on to take account for nipples?

Help!

Paul

You have the wheel…why not measure the spokes then compare its erd with that you are purchasing – then just add/subtract as necessary.

I use: http://www.wheelpro.co.uk/spokecalc/ …with fairly reliable results

I’ve not come across rim thickness being used as a variable before though – never seen any manufacturers give a measurement for it at least.

A fine point. I shall have a look at that tonight…

Using the Wheelpro calculator I get:

286.2
285.5

Another figure!!!!

Building my first wheel this week hopefully. I found the sapim spoke calculator to provide longer spokes than other online spoke calculators. In the end, I just trusted the wheel pro calculator as I have his book and he seems to know what he’s on about!

Sheldon Brown’s Spocalc

3 286.3 285.6

Closer to Wheelpro.

Beginning to think 286 may be my number.

🙂

Scratch that Spocalc is identical to Wheelpro.

3.00 286.2 285.5

Missed the Spoke hole Diameter.

I’ve found freespoke spot on. It also allows for weird offsets and crossovers and oddness useful when building fat wheels

Bedmaker- I’m using the information from the freespoke site, but I can’t get the calculator to work in my browser.

May try that at home tonight.

I used the formula that Roger Musson gives in his ebook and put that into a spreadsheet (OpenOffice Calc). I presume it’s the same calculation that his online spoke length calculator uses. It’s very easy to do and gives you full control over the process so that you don’t have to go onto the web. You can play around with various settings as well such as different crossing patterns.

I’ve built several sets of wheels and never had any problems with spoke length. It also centralises all the info and data on components and wheels that I have built into one file. It gives you a record for a particular spec. of wheel as well so you don’t have to calculate every time you build the same combo.

Previous to this I used to compare various online spoke length calculators and ended up with the same problem. I would say find one that you like and stick with that as they will all tend to give slightly different results depending on the algorithm used.

I can send further details of how to set up the spreadsheet if anyone is interested. It’s not rocket science and you don’t need to be a computer programmer to do it, just reasonably familiar with something like Excel.

If the calculator is asking for rim thickness, then its using an odd definition of ERD. As noted on the “ERD” page on the wheelpro site, the definition of “ERD” is not well standardised, so you should check how the calculator in question expects it to be measured, and then measure it yourself.

I think the differences in calculated lengths are explained by the differences in what ERD means, and to some extent, preference about what length is “ideal”.

Cool.

So assuming Wheelpro/Sheldon are correct at:

286.2
285.5

Would 286mm spokes left and right be OK?

I think it’s making sense…

P