Apart from the hottest days of summer, a base layer is always going to be part of your ride clothing.
Base layers are there to keep you comfortable and they do this in two ways: by trapping a layer of air next to your body to keep you warm and by transporting sweat away from your skin to keep you dry. If you want to get unnecessarily technical about it, a base layer forms the bottom of any multi-layer clothing system intended to manage the climate differential between the inside and outside of your garments.
That’s all well and good but how is a base layer different to the sort of vest you might wear under your normal clothes? Ultimately, the difference boils down to the materials used to make them. A base layer intended for cycling has to work harder to handle the temperatures and moisture you body generates when it’s pedalling a bike for long periods.
As such, base layers tend to be made from so-called ‘technical’ fabrics. These are fabrics constructed to have properties to ensure the surface next to your skin remains as warm and dry as possible while dealing with the sweat your body produces to cool itself.
The other difference is that a base layer has to work and remain comfortable while being worn underneath cycling jerseys and jackets that are typically a lot tighter than everyday clothing.
How do base layers work?
The man-made fabrics used for base layers are designed to suck sweat off your skin and shift it to the outer face of the cloth where it can be more easily evaporated off. This is what people mean when they talk about wicking.
Some do it by capillary action (the fabric’s inner face has lots of tiny voids to make it porous), while others do it using hydrophobic and/or hydrophilic coatings that repel/absorb moisture to move it through the garment.
Wool, the natural alternative, achieves the same result thanks to its internal construction, which has hydrophilic fibres held together inside a hydrophobic sheath.
But when it comes to choosing a base layer there are other things to consider besides the material it’s made from.
What to look for
Assuming you want sleeves, the first thing to consider is how long you want them to be. You probably won’t want a long-sleeved base layer if all your jerseys have short sleeves. Short-sleeved base layers will work with long- and short-sleeved jerseys but you may find the sleeves bunch up around your shoulders, especially underneath some of today’s closely tailored tops.
Whether you prefer short or long sleeves, you’re better off going for ones that use a raglan design. Raglan sleeves extend over the shoulder and all the way up to the collar. The design provides more freedom of movement for your arms and uses a diagonal seam that runs from your armpit to your collarbone, rather than circling your shoulder.
The other option is to go sleeveless. If you can’t bear to go without a base layer on even the hottest days, a sleeveless, string-vest style garment might be the way to go.
Some base layers have high collars but those that do are geared more towards winter use and may be too warm to wear in the summer months. A lighter base layer with a lower collar is more suitable for warmer weather and can be worn with a high-collared jersey/jacket and neck warmer when the mercury drops.
The bottom of the base layer is just as important as the top and it’s worthwhile looking for one that extends down a little further than the typical jersey. A base with a longer body provides more coverage but also more material to overlap, so you’re less likely to be exposed if your jersey rucks up or shorts slide down.
Seams and zips
As a general rule, the fewer the better. A base layer is worn next to your skin so you’ll want to avoid anything that might catch, nip, rub or irritate as much as possible.