OK, let me tell you first of all, I'm an oldish, slow, touring kind of cyclist. I have always worn a short sleeve cotton t-shirt in warm weather, and a long sleeve polypro top in cooler weather. I don't wear a jersey, because they are expensive and I don't need or want pockets, I use a pannier to store stuff.
Now I am seeing products like Underarmour that are polyester, but meant for hot weather, and claim to keep one cooler. Is this stuff really any better than cotton?
Yes. Anything is better than a cotton T shirt even a cheap bike jersey and you don't have to use the pockets. Cotton is a fine fabric except when you are sweating. It stays wet forever.
try california, nevada, arizona, new mexico law enforcement supply t'shirts or go to Campmor.com. there are various polyester weights, weaves and coatings. see backpacker magazine's website site for a review and ask rec.backcountry archives.
the poly is terrific-for example a thunderstorm soaking doesn't chill after the searing heat didn't kill my energy.
the effect depends a lot on your body insulation-thin reduced fat people benefit more than fat people. with no discernable body fat- i ahve a sweet spectrum at 50-60 degrees where after crawling out of the tent and starting tea in the coolness, the poly effect is so pronounced that i react by savoring the effect. a fat person may have a spectrum at 40 degrees so the poly positive would not be as noticeable. the cotton problem is a wet suit function-the absorbed wetness warms to 98 and no heat transfer occurs.
