Base Layers: The Underappreciated Cycling Essential

Rode without base layers for years. Just threw on jerseys over bare skin. Then someone lent me a proper base layer for a cold early-morning ride. The difference was immediate and embarrassing — how had I been missing this basic piece of kit?

What Base Layers Do

The first layer against your skin serves two purposes: wick sweat away and regulate temperature. A jersey alone does neither well. Cotton does neither at all.

Sweat against skin makes you cold when you stop and clammy when you’re moving. A base layer moves that moisture outward to where it can evaporate. You stay drier and more comfortable.

Material Options

Merino Wool

Natural fiber that regulates temperature beautifully. Warm when cold, doesn’t overheat when warm. Naturally antibacterial so it doesn’t smell after multiple uses. That’s what makes merino endearing to us multi-day touring types — one shirt does a whole trip.

Downsides: more expensive than synthetics, dries slower when wet, requires more careful washing.

Synthetic (Polyester Blends)

Lightweight, cheap, dries incredibly fast. Most cycling-specific base layers are synthetic. Great for high-output efforts where you’re generating tons of sweat.

Downsides: develops odor faster, less temperature-regulating than wool, feels less pleasant against skin (to me anyway).

Blends

Wool-synthetic blends try to capture benefits of both. Often successful. More durable than pure merino, better temperature regulation than pure synthetic.

Choosing by Weather

Hot Weather

Lightweight mesh or sleeveless. Sounds counterintuitive — adding a layer in heat? But the wicking makes a difference. Sweat evaporates instead of soaking your jersey.

Moderate Weather

Short sleeve or sleeveless, medium weight. This is the most versatile option. I wear one 9 months of the year.

Cold Weather

Long sleeve, heavier weight. Provides insulation as well as moisture management. Thermal base layers trap warm air while still moving sweat.

Variable Conditions

When weather is unpredictable, a medium-weight merino works for everything. It self-regulates better than synthetics.

Fit Matters

Base layers should be snug without being constricting. Loose base layers don’t wick properly — there needs to be skin contact. But too tight restricts movement and becomes uncomfortable.

Length matters for cycling specifically. Long enough to stay tucked in your shorts while bent over handlebars. Short base layers ride up and expose your lower back — unpleasant in cold weather.

Brands That Work

Rapha: Their merino base layers are expensive and excellent. Worth the investment if budget allows.

Castelli: Good synthetic options, many weights and styles. Widely available.

Craft: Swedish brand with excellent temperature regulation. Popular in cold-weather cycling communities.

Smartwool: Not cycling-specific but their merino base layers work perfectly. Often cheaper than cycling brands for equivalent quality.

Care and Longevity

Follow washing instructions. Merino requires cold water and gentle cycles. Synthetics are more forgiving but still benefit from cool water.

No fabric softener — it coats fibers and ruins wicking properties. Air dry when possible; dryers are harder on technical fabrics.

Properly cared for, a quality base layer lasts years. I’m still wearing a Rapha merino I bought five years ago.

How Many Do You Need?

Minimum: one for cold weather, one for moderate weather. That covers most situations.

Better: add a lightweight summer option and a backup for laundry days. Four base layers handles year-round riding comfortably.

My rotation: two merino for cold weather, two synthetic for warm weather, one for each season in the wash at any given time.