The wheel is a strange construction of cast aluminum hub and steel spokes. I had the welding instructor at a local makerspace do the welding for me. It did pop a little due to the casting having bubbles, but he had no problem welding it. I personally would of not attempted as aluminum is very tricky to weld. At home, I drilled and tapped the holes to 4mm and was able to mount the hub. There's a little gap between the hub and the horn button but I can fill that in with a ABS printed part (once I can get one of my two printers working again).