Advanced spoke length calculations
- A real-world calculation for a mixed straight pull / J-bend hub design -

Recently, I was in touch with a fellow foreign wheel builder from France, that was starting a wheel project with Aivee Edition One road hubs. Looking at their mixed straight pull / J-bend flange design, the main question was obviously how to introduce such a unique hub design to the App Spokecalc and especially inside the SpokeCalc spoke calculator to get correct spoke lengths for this project.

Aivee Edition One road hub
The uniquely designed Aivee Edition One road hub. Foto: Tregoride Cycles

The Aivee

Looking at the company's history, although this French brand of high performance hubs is relatively new to the scene, no one can deny that the team of cycling and technology enthusiasts as they call themselves made a substantial effort impressively fast by creating a broad range of bike hubs and corresponding spare parts.

Moreover, with their premium wheel truing stand it seems that they are gradually expanding to the field of high end tools. As can be read from their website, this tool is just a stepping stone of creating a broader range of special wheel building tools. Judging from the quality they offer at the moment, it is safe to expect some interesting results, because they certainly have their own way of doing things!

Understanding the unique hub design

Looking at the Aivee's technical drawing below, the Edition One hubs certainly combine best of the two distinct hub types. While the front hub is designed to be used with radially laced straght pull spokes, that is also the case for the rear, non-drive wheel side. On the other hand, the drive side of the Edition One road hub was designed for J-bend spokes. And as such, this article is about to focus on how to deal with such hub designs in the spoke calculator.

Aivee Edition One hubs technical drawing datasheet
Technical drawing of a mixed straight-pull / J-bend rear hub design.

According to Aivee, such hub design offers a significant weight gain with no losses on solidity and even an increasing of lateral rigidity of wheel. This looks to be the case as the rear hub itself barely weighs 180 g give or take in total. At the same time, bringing the straight pull spokes to the table clearly indicates that they were also after improved aérodynamics.

Looking at the drive side of this rear hub, J-bend spokes on the freewheel side permit a decreasing of stress between spoke and hub, and an improved torque transmission during pedaling stroke while sustaining a lateral rigidity of wheel.

The rim and lacing choice

Since I wanted to demonstrate a real-world 2-step spoke calculation for this uniquely designed rear hub, I opted to go with the same rim choice. And as it turns out, for this particular wheel project, an asymmetric, rim brake Duke Baccara 42 Rb SLR2 carbon rim with 24 spoke holes was used. Kindly, this fellow wheel builder has also provided me with a complete component summary screenshot from the App Spokecalc. Right about everything we need for the spoke calculation, ain't it?

Duke Baccara 42 Rb SLR2
The rim choice datasheet screenshot from the App Spokecalc.

Running the spoke calculations

While the front Aivee Edition One hub can undoubtedly be treated as a straight pull type hub, this isn't really the case for the rear hub. Therefore, from a spoke calculator algorithm viewpoint, like our fellow wheel builder suggested when he contacted me, we face a slight limitation as we cannot run a mixed straight pull and a classic hub type calculation at the same time.

But there are basically (at least) two alternatives. The first one is to do a 2-step spoke calculation for each hub side at a time. The thing is that spoke calculator always does that, so apart from having two SpokeCalc's windows open in our browser and ignoring the calculation of the wheel side we are not after, it shouldn't be so complex, right? The other way is by treating this hub as a normal classic hub type and use a slight correction for a non-drive straight pull radial spokes.

But let's start with the easier part. So, to get the drive side spoke length, we first select a rear wheel and click on the Classic hub type checkbox at the top of the SpokeCalc. Then we initially run the calculator using initial rim/hub's dimensions in combination with 2-cross 24H lacing setup which results in drive side J-bend spokes coming at 267.5 mm. At that point, just ignore the left side result (275.4 mm) as we are still in the J-bend hub type mode and also with a selected 2-cross lacing pattern. In the next step, we should get the non-drive side spoke length.

Spoke calculation
The first step is the drive side spoke calculation. Ignore the left side calculation.

Note: in the free version of the SpokeCalc online spoke calculator, one can only select one lacing pattern and one spoke count for both wheel sides. So keep that in mind when making a multistep calculation, and if needed, just open separate browser windows for the same spoke calculation.

Now open another browser window of the SpokeCalc page and again select a rear wheel but now make sure to check the Straight pull hub type. Almost all hub data stays except for the Spoke offset, where you enter a zero values (0 mm). This is the case for all radially laced straight pull hubs. Continue selecting 24 spoke holes and a radial lacing pattern which should get you a result of 268.3 mm for the non-drive side. I blurred the unneeded drive side spoke length calculation (253.71 mm), and as such it should be ignored completely.

Spoke calculation
The second step of this calculation is getting the non-drive radial straight pull spoke lengths.

That's it, basically. Leaving the process of rounding up or down to your own preference, the spoke calculator tells us that we will need twelve radial straight pull spokes for the non-drive side somewhere in range of 268.3 mm and the same amount of classic spokes to be laced with a 2-cross spoke pattern on the drive side in length of 267.5 mm. Why such a fuss anyways?

Here comes the bonus tip, the trick I mentioned in the first paragraph under this heading. If you don't wish to restart the whole calculation in the new browser window, the trick here is to stay inside the Classic hub type mode and just switch lacing from 2-cross to Radial. Afterwards, pressing again the Calculate button should get you a NDS spoke length of 266.97 mm. Not quite there yet, as, remember, we are after the 268.3 mm, but the difference between radial straight pull spokes and radial J-bend spokes is actually exactly one half of the spoke hole diameter. From the SpokeCalc's calculations algorithm viewpoint, this is the only difference for radially laced spokes of these two distinct hubtypes. Add this number to the calculated spoke length of a radial classic spoke and you again come at 268.3mm for a radial straight pull spoke.

Aivee Edition One hubs and Duke Baccarra road carbon wheelset
Here's the final result. One beautiful wheelset that any customer should be happy with! Foto: Tregoride Cycles

Simplifying the process with the App SpokeCalc

Let's now take this calculation on the whole new level. Knowing now of this little bonus trick I mentioned above, once inside the App SpokeCalc, you will be able to complete this calculation in just one step as it lets you select the spoke count and the lacing pattern for each side at the same time.

Although the base algorithm of the spoke calculator is the same, inside this membership based web app, you have lots of features that will noticably simplify your wheel building process. Follow the app's development on Instagram or read more on the official landing page.

App SpokeCalc, the total wheelbuilding app
Advanced lacing section inside the App SpokeCalc's spoke calculator.

Final thoughts

Hope this project cleared your mind of any fears and worries regarding using a spoke calculator in a different than the usual way. In fact, some spoke calculations will inevitably be a multistep process and therefore it helps understanding the logics behind the tool you are using to get spoke lengths. Having done multiple 2:1 wheel setup spoke calculations, from my experience, once you start experimenting and coming to the same results with different approaches, that is when you actually learn something!

At this point I would like to give a big thanks to our friend in France, Tregoride cycles, for supplying me with nice imagery and also an actual technical data. Check him on instagram!

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