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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They are great for changeable weather and mid-temperature but I also would not endorse using them in really hot weather.
I know the theory of wicking but experience suggests that after a certain point it is outweighed by having another layer on your body. have various Giordana and Craft vests but don't wear them when it gets really hot, like above 35C.
Good summer jerseys are also designed to wick moisture away from the body and allow it evaporate it so I don't see how adding another stage to the process is going to help.
I've been riding the UNDshirt and UNDREcycle. The UNDRecycle is incredibly comfortable as well. A great piece. As far as the discussion on whether or not to wear a base layer in high temps I'd add that while temps are a consideration, humidity is a bigger concern. If the relative humidity is high I find base layers to be stifling. My skin wants to breath and the best way to do that when the temp and dew point are both close to each other and high would be to ride naked. Since that's not legal or Rule compliant I opt out of the base layer. However, when the air is dry and/or cool the base layer is the way to wick. Plus it's oh so pro.
Any other Colorado cyclists with opinions?? The relative humidity here is typically very low...desert like. These materials sound like a a good idea.
Its funny that I only found out what a base layer was a year after getting my first bike. Don't think Ill ever need one while I live in Tucson. but its good to know that I might when I move to colder climates.
@RedRanger
Im guessing they would work better in humid areas. its so damn dry here I rarely feel sweat until I walk into the comfort of a ACed building.
I've used DeFeet UnDShirts for years, and they are an indispensable item in my opinion. Looking forward to testing the Wool version in the cold here soon... DeFeet really have the accessories game sorted, their socks, warmers and shoe covers get a lot of love from the Welliminati I ride with too.
I've always looked at undershirt with some suspicion, doubting it's benefit. May be it's time for me to pick one and enjoy a comfortable ride in the sticky weather
@RedRanger
I've found that in quite warm (33C) and very humid Singapore that a base layer doesn't feel nearly as nice as just a light short sleeve over bibs. No matter what you wear, you're going to be wet after an hour anyway.
@Marko
Agree with that - summer here is when the humidity gets very high, so maybe that's what makes the base layers less comfortable.
On a ride the other week we were sweating so much we had prune-fingers after the first hour.
@Marcus
Yeah, I tried one of those but found it chafed my back.