How it works
Rayons is a highly visual tool for calculating bicycle spoke lengths. In the app, you are presented with drawings of wheel components. From these drawings you can see exactly what measurements are necessary to accurately calculate a spoke length. The fun part is, you get to manipulate the components yourself to enter the dimensions. The resultant spoke length is always updated in real-time. Once you are satisfied with component dimensions just enter a name for the configuration and save it in the app for future reference.
Finding the length
Rayons uses a very well known trigonometric formula to calculate the proper spoke length based on the component dimensions entered into the app. Some of these component dimensions are published by each manufacturer. However, Rayons highly recommends that you make your own measurements. One reason for this is because much of the information published by component manufacturers is out of date. In addition, this information often varies between component models or even within a batch of the same model. If the input dimensions are not accurate the calculated spoke length can be skewed considerably.
For the best results, make your own measurements.
The formula, which is published in the app, does have a set of limitations. These limitations are documented here and in the app.
All dimensions are in millimeters down to the tenth. This view shows only a few of the measurements that are required to calculate a spoke length. Settings contains some important but less frequently changed dimensions such as, spoke hole diameter. Wheel Sets contains your saved wheel set configurations.
Front Hub View
The effective rim diameter and the spoke hole offset are the most important measurements for a rim. Several rim shapes are supported by selecting Settings in the app. Asymmetric rims are also supported.
Front Rim View
The drawings in Rayons are dynamic and change in real-time when the dimension changes. This gives a sense of how each component dimension affects the spoke length. As you can see, there are two types of controls for changing dimensions. This makes it easy to control dimensions down to 0.1 mm.
Dynamic Drawings
The Perfect Length
The Rayons app calculates the length for the perfect spoke, hub, and rim. In other words, as if they are made out of materials that do not elongate, deform or compress. In reality, we know that all of these things happen to a degree when we build a wheel. There are a very large set of components to choose from. Material quality and tolerances may vary by manufacturer or between component models. Given these large set of variables it becomes an engineering exercise to take the “perfect length” and apply it to a given wheel build. This work is best left to the knowledge and experience of the wheel builder.
Accessibility
Rayons supports some iOS accessibility features in the app. Dark mode is also supported.