As indispensable and overlooked as the gilet, the undervest is the only piece of cycling kit that comes with me on every single ride, year round, in hot, in cold, in wet, or in dry. While one could be forgiven for assuming an undervest lives out its life as an insulation layer, the undervest serves a critical, more fundamental purpose: as a wicking layer.
If you’ve ever had the misfortune of carrying a gallon jug of water, you will have noticed that water is not particularly light, nor particularly dry. If you’ve suffered the further indignation of having said gallon jug of water poured over your head after making a pithy remark, you will have noticed that the introduction of water to your clothing makes them both heavier and less warm. As cyclists, these characteristics don’t do much for us in the way of making our sport easier from the perspective that sweat is made up largely of water and thus has a tendency to make the clothing we’re wearing both wet and heavy. Enter the base layer, whose specialty is not so much in keeping us warm, but keeping us dry.
If I’ve understood physics correctly, these magical fabrics are designed to maximize the capillary action of fluids by sucking the water in our sweat away from the skin and towards the outside of the fabric where it can either evaporate or at least stop touching us. Even though the fabrics in our jerseys and bibs are heralded as being able to perform this task on their own, they are busy doing other things as well, and I find that using a layer dedicated to this purpose improves the effect greatly.
To be fair, though, the thought of wearing an undervest – or any additional thread of clothing for that matter – is far from inviting when kitting up in the middle of Summer. This is where DeFeet really shines with their multiple weights of undershirts, each targeted at a different temperature range. From the cooler months of September, through Winter and on into Spring, the Un-D-Shurt tank base layer is my go-to garment, keeping me dry but also adding a bit of warmth to stave off the cool air around Puget Sound. Once the mercury starts rising, however, I switch to the Un-D-Lite, which is much more lightweight and purpose-driven towards wicking rather than also insulating.
With both of these pieces, they are so stretchy, soft, comfortable, and good at keeping your skin dry, I never even notice I’m wearing them. I’d like to meet whomever figured out how to make this stuff; their brains must be so big, I bet you can spot it when you look in their ear.
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Good tip to remember. Wearing a Craft mesh (hot weather) sleeveless layer feels great. Especially when you want to pull your jersey off in a parking lot after riding.
So do the "cooling" ones actually make you feel cooler?
I totally get the idea behind more wicking = more evaporation = cooler feeling, but the idea of adding more layers in the hot weather makes my brain hurt.
@mcsqueak
If you're talking about those ICE ones possibly yes maybe. Someone (LG?) makes shoes with an insole with xylitol, which is the sweetener used in sugar-free gum, that supposedly cools your feet. The wonders of science.
Interesting. I spend most of my time riding around 6000'-7500' here in Colorado, so wicked ranges of temperatures are a normal occurence. This material might be able to do double duty between warnth and wicking. This weekend I put in about 75K at 6200'-10200' on gravel on my 'Cross bike and was cold on the one downhill because of sweat and wind. Might be something to use if I can find it here locally. The Copper Triangle is this weekend and the high temp is only about 21C with a kickoff temp of 7C.
Wow, I was just out doing one of the local climbs with the temp hovering just below 100F with my training partner and the Defeet under shirt that is made out of some kind of material that is cool to the touch was a topic of discussion.
@mcsqueak
Look into the great Australian invention - the Coolgardie Safe. Evaporation on the outside = cooler on the inside. Something to do with heat transfer - not sure if this applies to wicking - but it might!
while i completely agree that base layers are incredible in general, i dislike them for warm weather. i have some great merino ones that i adore in anything around 20 degrees or less. between 20-30, i have a tight-fitting, synthetic, super-light layer that does a great job of wicking. above 30, forget about it. i've tried and i just can't do it. day-to-day comparisons in the same jersey both with/without a base layer tell me that when it's above 30 (and often, approaching 40), and the humidity is at 80+ percent, wearing an extra layer is stupid. both layers are soaked with sweat before too long and then you're really hating life.
the main thing for me is that when it's that hot and i have a base layer on, all i end up doing is unzipping my jersey and cruising around with the layer showing. looks better than with no base layer, but in that situation, i prefer to just ditch the layer and leave the jersey zipped (or when climbing, unzip and enjoy being much cooler than with a base layer).
Any time you're exerting yourself and experiencing any temperature changes, a wicking layer is a good thing. Only you can decide whether you want a(nother) wicking layer under your jersey on a given day. I'm more inclined to choose it if there's the threat of a chill from a change in weather or airspeed. I wouldn't start "stacking" for a flat ride on a hot still day.
Non-cycling-related: a light cotton shirt will cool your ass in the desert. Sometimes rapid evaporation right next to your skin is heavenly.
^^ I.e., what he said.
When I was young, dumb and full of .....life I had the opportunity to learn the error of my ways (or rather, the error of my drunken mouth) by having the odd container of fluid or, in one instance, a backhand to enlighten me. I too learnt that said fluid does increase body weight as well as making one colder when stumbling out into the night. It can get a bit sticky when it dries as well.
I also discovered undervests several years ago. I have an old Cima vest that I've been using for about 15yrs that still insulates well on cooler mornings. I also have various other brands for use through the seasons, i.e. Autumn to Spring - Canterbury, Castelli, DHB and a Santini. All work flawlessly for their intended purpose. I must admit though that I have never tried using one in the midst of a Sydney summer ride. I've always just gone with the jersey. Perhaps it's worth a try then.