For those of you that haven't heard about wearing CoolMax under your leather riding suits, you’re missing out for two reasons: cost and comfort.
When you wear a leather suit in hot weather you’re going to sweat in order to cool down. The problem is that if you wear cotton under your leathers, the cotton locally absorbs the moisture (until saturated) and holds it next to your skin while the leather absorbs it. You won’t be very comfortable when wet, and eventually the suit will begin to smell funky and need replacement from repeatedly absorbed perspiration.
If you wear a high-tech wicking fabric such as CoolMax under your leathers, the perspiration is transported away to vented areas where it can cool you by being evaporated away. So unlike cotton, it moves sweat away from warmer areas with low air flow (like your butt.)
In short, absorbent fabrics soak up moisture and hold on to it, wicking fabrics transfer moisture to drier areas, without getting saturated. This behavior allows the air flow at the suit openings and the perforations of vented suits to more quickly evaporate the moisture away - even from areas where there is no air flow. In addition, Coolmax has a silky texture that feels nice against your skin, and it’s somewhat slippery which makes it easier to climb in and out of leathers.
You can see this behavior after you wash it. When you hang it up, the water isn’t held, so the excess drips off quickly. The wicking action distribute the remaining water over the whole surface area, so it evaporates in a few minutes, unlike cotton which will stay moist for a much longer time.
Kushitani makes their inner suit out of CoolMax and Dainese supplies one with their top-of-the-line T-Age suits. Bohn makes one also.
Lightweight shirts, pants, underwear and socks made of Coolmax fabric are considered essential for tennis, golf, skiing, hiking and and cycling - so check your local shops first. There are other fabric materials that have similar wicking properties but Coolmax’s moisture management is superior.