The bikes stand upright inside the van and the helmets ride on the floor with all their stalks sticking up. This usually works out well, but on our last trip my helmet rolled under my bike and rubbed the foam ball surrounding its mic against the chain, producing a result so awful that I had to install new foam.
For posterity, here’s the current state of the electret mic and its mount:
The foam comes from a sheet of Sonex acoustic foam baffle, snipped into a reasonable approximation of a ball, with a slit deep enough to surround the mic, and a cable tie holding it closed:
For what it’s worth, I’ve found that excessive wind noise correlates with too much mic gain. The mic rides about a finger’s width from the corner of my mouth, I talk at a normal volume, the amp supplies about 20 dB of gain, and we have no trouble with wind noise. The amp gain depends on the mic sensitivity, so your results will certainly differ; these mics came from the heap with no specs whatsoever.
I suppose wind noise also depends on the bike’s speed, but when I’m going that fast I don’t have enough brain or lungs left over to hold a conversation…