Base Layers: Out Of Sight, Out Of Mind

We delve into the world of cycling base layers and discuss why you should consider pulling one on – even when a heatwave strikes.

Ah, the base layer; that most inconspicuous and misunderstood garment of the cycling wardrobe. Base layers have proven to be a surprisingly divisive subject. Some won't clip in without wearing one; others just don't get how another layer can actually keep you cool and comfortable.

We thought we'd shed a little light on how they work and when to use them – even if the temperature hots up.

If you're into a variety of outdoor sports such as skiing or mountaineering, you probably already have some concept of layering your kit, especially in winter.

When it's cool, multiple layers help trap air, which warms up and keeps you toasty. Meanwhile, specifically designed layers can also aid the transfer of sweat from the skin to an outer garment – a process called wicking. This keeps you drier and being dry is obviously warmer than being wet.

So far, so good. Base layers make a lot of sense in the cold. What most people don't understand, or even consider, is the role of base layers during mild and hot weather.

First off, not all base layers are created equal. Some are designed to actively cool you; some are designed to passively regulate temperature, some are designed to move moisture and some are designed for warmth. You need a very different base layer for 35°C than 2°C.

From enhancing your comfort to increased performance and protection, there are plenty of reasons for wearing a base layer year-round.

Moisture management

Either through capillary action or chemical treatments applied to the material, a base layer absorbs moisture (your sweat), getting it away from the skin where it can evaporate. This is that mysterious 'wicking' word bandied around on product specifications.

Imagine, if you will, climbing a hill in direct sunlight without a base layer. As the intensity ramps up, you're soaking your favourite Castelli jersey with sweat. Then you plunge down the shaded northern flanks of the hill – that hot sweat turns into a cold, wet compress. As well as being chilly and uncomfortable, it's just a bit unattractive.

By putting a moisture management base layer between skin and jersey – just as you'll see the pros doing at Le Tour – that next-to-skin saturation is mitigated and the moisture can be freed into the air.

Your base layer also absorbs the salts and minerals you sweat out, stopping them from blocking the pores in your breathable jersey.

Our best moisture management base layer are the Pro Mesh these can be found in men's base layers and women's base layers variations, it uses capillary action to move sweat away from the skin. It also has a 3D knit meaning it can trap air for better temperature management. Speaking of which…

Temperature management

By having air pockets in a base layer, the skin stays drier and more comfortable thanks to your body being able to better regulate its temperature. Old-fashioned style string vests, but in modern fabrics, are best at temperature regulation.

Check out the Castelli Core Mesh base layer for the perfect next-to-skin experience that keeps your body nice and dry all year round.


Another area where's there's more than meets the eye, the humble base layer can perform a variety of valuable protective tasks.

Slip sliding away

If you crash with just a jersey on, you will almost certainly get road-rash friction burns and possibly even melted polyester jersey sticking to your skin. Definitely not desirable. Using a base layer allows a lot of the friction to be dissipated, meaning you're less likely to get superficial – and painful – injuries.

There are even some who believe that a base layer can help reduce the chances of a broken collarbone in a crash. While this might be more to do with the fact that experienced riders, who happen to wear base layers, know to roll in a crash, we still think you're better off crashing a base layer than not. Of course, not crashing at all is the gold standard to which we should all aspire!

Feeling hot, hot, hot

It's a gloriously hot sunny day. You wear your open mesh cycling jersey to keep yourself cool and – ouch! You get burnt through your jersey. Not only are the long-term health risks of sunburn pretty dire reading, if you're on a long ride and you get burnt, you get hot, dehydrated and your performance suffers. Then, because you're going slower, you have even more sun exposure, making all the symptoms worse. Avoid that nasty pattern by wearing a base layer.

As a caveat, it's worth noting that Castelli does offer some jerseys that are designed to be worn next to the skin. The Climbers 2.0 jersey, for instance, is so light that it wicks, breathes and dries almost instantly – just like our base layers. Do remember to use sunscreen, though.

Cool runnings

This is the one most people think about and really, it's a combination of trapped air and moisture management but add a little bit of extra insulation and you've got a layer fit for the winter warrior. Usually known simply as 'thermals' Castelli's warmest base layer is the aptly named Flanders Warm, which is part of the winter collection.

Virtue in modesty

Some cycling jerseys are very see through and both men and women can find this a little disconcerting. A base layer under a jersey will smooth out the worst of your lumps and bumps, hide your bra, HRM or straggly chest hair, meaning you and your mates will all be more comfortable in the cafe mid ride.

This is probably also a good time to mention the Rosso Corsa Cycling Bra's. These cycling-specific sports bras work like our base layers, offering maximum ventilation and moisture management as well as modesty with a design created especially for light cycling specific support while out on the bike.

Take a breath

If you're still not convinced, there's another very good reason for wearing a base layer on cool wet or windy days. Most technical jackets and mid-to-outer layers rely on a base layer for best performance. Something like the Gabba or the Tempesta rain jacket can't do its job properly when worn next to the skin.

Breathable garments rely on the fact that moisture vapour is 'smaller' than moisture droplets. A base layer helps regulate your sweat, keeping it in vapour form to allow your breathable jacket or jersey to work at its best.