MarkJohnston said:
I'm building my first wheel too. I thought the 12G spokes we're stronger? It's damn hard to find the correct size 12G. What about butted spokes or double butted? Damn the washers, the sounds annoying. Why is chalo always saying the 12G are weaker? I put 6000 km on my hub motor and never had spoke issues. My rim did fail but that's because I brake super hard and am psycho with my stuff.
Remember that spokes like these don't "hold up the wheel" like columns, or like a solid-spoked cast wheel. They act as tensioned "cables" something like a suspension bridge, and if they aren't tensioned sufficiently they won't support the rim correctly. A simplified way of looking at it is that they don't push the hub up from the rim down at the bottom of the wheel, they pull up the hub from the rim at the top of the wheel, essentially hanging the bike from the top of the rims (as I said, simplified
).
Thicker spokes are only stronger if your rim and spoke flange on the hub are both designed to use them, and can take the forces from the spokes when they are tensioned correcttly.
Spokes that are thicker than the rim can support can cause rim damage when tensioned correctly. The nipple is pulled by the spoke so hard that it deforms or even cracks the rim around the nipple hole. This then lets the nipple turn and loosen the spoke, until the nipple falls off inside the rim and the spoke hangs loose (or enough spokes loosen for the wheel to come apart, or for less loose spokes in one section of rim they can then poke holes in the tube).
If you glue the nipples to the spokes so they can't turn, they won't fall off, but the spokes are still loose because the rim is damaged / deformed at the nipple hole from the overtension.
If the spokes are not tightened enough to deform the rim (but require this tension to operate correctly) then they will not support the wheel, and the same problems arise as if they were tight enough and damaged the rim and became loose instead.
Loose spokes may also bend repeatedly at the elbow, and break there, next to the spoke flange of the hub.
If the rim can handle the higher tension but the spoke flange can't, the flange may shear off the hub, or rip chunks out around the elbow holes.
Using the right spokes for the rim and spoke flange prevents these problems and makes a stronger wheel. Usually the right spokes are thinner rather than thicker. 14-15g butted or double-butted spokes would be a good choice for most typical ebike wheel builds. Thinner might work even better, depending on usage and specific rim/hub being used.
Butted just means that the end (elbow) is thicker, double-butted means both ends are thicker. This can be done to fit a specific hole size in a flange (or nipple) but still use thinner long part of the spoke so it tensions correctly.
If you find a well-built wheel with thinner spokes is failing from a very heavy load (hundreds to thousands of pounds), you would need to use heavier duty rims and hubs designed for the thicker spokes in order to use the thicker spokes without wheel failures.
But before moving to heavier duty wheels, looking at the specific failure mode would be good, to see what is breaking and why, to make sure the right fix is applied.