This time it’s a new rear wheel for the fixed gear. I’m using my old Suzue “1 B” hub (I think it’s an SIL-SP), which accepts 36 spokes (not 32, as I previously thought). The rim is an Alexrims DA22, which I got by disassembling the rear wheel of a wheelset I bought for Kathleen’s mom’s old bike, that Kathleen used to ride. The corresponding front wheel is currently spaced for a mountain bike fork. I’ll probably have more to say on here when I figure out what has to happen to adjust its width (i.e., can I just remove a spacer or two or is the hub just plain too wide?). I have 18 286mm spokes and 18 287mm spokes left over from disassembling the old rear wheel, but Dan Halem’s spoke length calculator tells me I need 282.7mm spokes for 3-cross lacing and 293.1mm for 4-cross lacing. This convinces me that the spokes I already have won’t work, although I’m tempted to try anyways to see what goes wrong.
There’s a good bit of Wheel Lacing Information at this site, including Spoke Length Tolerances and Fixes for Some Problems. Take-away messages seem to be that spokes are only too short if you can’t get them started. It seems that once they’re started there’s enough stretch and the threads are good enough that the wheel will be strong, even if some threads are showing. It’s harder to derive a rule of thumb for when spokes are too long, but the old rear wheel on my fixed gear had 2~3mm of spoke sticking beyond the end of the nipple (double walled rim + rim strip = no problem) and it never had a failure related to pulling through the nipple. Thus, I think visible threads sticking out the other side are also tolerable.