Calculating spoke length correctly is done by using an online calculator. Learn how to measure spoke length when building a bicycle wheel in this free video on bicycle wheel building.
Alright, the online spoke calculator, this particular example comes from United Bicycle Institute, is a valuable tool for accurately calculating your spokes. We've taken our measurements and we want to plug them into the calculator to see what our exact spoke length number is. First, I'll do the ERDR Effective Rim Diameter. We measured it as 542 millimeters. Next we'll do our hub flange diameter. We measured that at 38 millimeters. Now out center to flange number which we measured as 32 millimeters. We counted 32 spokes. We know it?s a 32 hole wheel. And we've decided on a three cross calculation, that's a very typical calculation for a front wheel on a mountain bike. Ask it to calculate and we get 265 millimeters as our accurate length. Now I should point out that we've calculated a front wheel in which both flanged are symmetrically spaced, they're equal on both sides. If we were doing a rear wheel or a mountain bike front wheel that had a disc brake, those flange numbers will be different. The center to flange numbers will likely be different and in some cases even the flange diameter numbers can be different. It?s important to calculate each side of each wheel to give you an accurate number.