There are a few threads about spoke length calculation; and most refer to online spoke calculation tools.Thank you! This is a great help! The double butted spokes are stronger? And maybe you could assist me with your excel sheet? I really have no idea what length I need other then that I know the ones I have are flat out too short.
Sometimes the online tools though, would ask for a selection of make/model of hub or rim, from a pull-down menu; or otherwise it seemed that my computer could not make the “go” button work(?).
The calculation is based on the dimensions of the rim and hub, (including number of holes), and the pattern of how many spokes cross another, (e.g., 3 or 4). It uses the law of cosines (a law) and Pythagoras’ theorem (just a theory, that I am still not too sure about).
I did my own calculation for a 28” rim and hub and compared what was more common online (thinking maybe every one else’s calculation could be better than mine), and for the 28” rims purchased 292mm spokes. Probably could have gone with 291 or 292; not sure about 630mm/27” rims though.
Maybe the double-butted spokes that are skinnier in the middle might be lighter weight and cause less air drag?