Black Diamond Rhythm Tee Review

Black Diamond set out to make the lightest running shirt possible with the benefits of Merino wool. At 3.3 ounces, the Rhythm Tee is wonderfully light, very breathable, and our absolute favorite for layering. While the price is steep, this piece offers more than most running shirts in the form of Merino wool benefits. A simple construction paired with amazing stretch creates a layer that doesn't chafe with a pack or layers, has no excessive stitching (thus reducing weight and increasing durability), and breathes well while wicking moisture. It could use some added reflective banding, but other than that it's simply stellar.

Performance Comparison

Comfort

The Rhythm Tee topped the charts in overall comfort, both when pulling it on for the first time and when performing on the trail. Unlike some Merino wool shirts, there is no itch or discomfort against the skin here. At 3.3 ounces, the lofty fabric feels almost cloudlike and is barely noticeable.

It can't be said enough; the stretch and shape retention of this shirt are ridiculous. While our tester, at 5'10" and 155lb, wore a medium, he likely could have comfortably worn a small or large. Smooth and soft flatlock seams stretch with the Merino wool and nylon fabric, and however perplexing it may be, the shirt kept its form. Even the soft thread used on the flatlock seams contributed to the four directional stretch. Outperforming many shirts with body-mapped mesh panels and underarm gussets, this tee has a very simple design with side seams and raglan sleeves connecting to the collar. Fewer seams, paired with the qualities of the Nuyarn fabric, make for a more comfortable and durable ride by eliminating weak points.

While we worried that the stretch of the Rhythm Tee might cause bunching, and shape retention made us think of discomfort and bunching, it fit comfortably beneath a light windbreaker, fleece hoody, and three layer shell. The highly breathable fabric with its natural wicking properties led us to ditch our normal long underwear. As the lifts stopped spinning in the spring, we lived in this shirt for spring ski missions, often leaving the house on a bike, skinning for hours, ripping down our objective, and biking home.

Breathability

There are shirts that feature strategic mesh paneling to promote ventilation, and there are shirts that use a uniform polyester blend to capitalize on evaporative cooling. This shirt does not fall into either of these categories. The Rhythm Tee is made with Nuyarn, a fabric that uses Merino wool drafted over a synthetic nylon core. On the outside of the fiber is Merino wool, an excellent wicking agent, while on the inside is highly stretchable nylon. This makes the entire shirt permeable to airflow and equips it with the thermoregulating benefits of Merino wool.

If you have enjoyed the breathability of other Merino wool shirts but felt uncertain about the comfort or durability, this shirt may change your mind. During hill repeats in the heat, it wicked moisture and promoted evaporative cooling. And, while nordic skiing on the spring crust in Ashcroft, CO, it retained enough body heat to keep our testers warm while not sweating through. The best of both worlds.

Drying Speed

Our standardized drying speed test helped us compare polyester shirts surprisingly well, but it didn't take into account the feel of the damp material against the skin. While the Rhythm Tee did not exhibit the same drying capabilities as some of the polyester shirts in the mix, on the trails, it performed phenomenally.

When wet, this shirt held 63% of its weight in water. After the first spin cycle, it retained 30% of its weight in water, and after ten minutes in the dryer, only 9% of the shirt's weight in moisture remained. The notable difference here is that at 9%, it felt completely dry to the touch, while polyester shirts feel damp with between 2%- 5% of their weight in water remaining.

Outside of our kitchen lab test, we never reached a point of discomfort while wearing the Rhythm. We did note, however, that when properly wet from a spring rainstorm, the fibers stretched out, and the shirt got larger — though it returned to its normal shape and size as it dried. When wet and stretched out, the fibers were more susceptible to degradation. Since wool is a natural fiber and not a plastic, we tried to avoid direct friction between pack and shirt when it was wet.

Features & Versatility

This is one versatile base layer, so much so that it performs phenomenally as a running shirt. We wore it during both hot yoga and freezing dawn patrol missions, and it crushed. For 50 kilometer races and track workouts, same deal. From rock climbing to mountain biking, the comfort and performance of the Rhythm Tee rang true. It is a highly effective base layer for all seasons.

With a tag-less neck and an integrated collar sweatband that stretches with the shirt, comfort was spared at no cost. Sadly, though, the Rhythm Tee doesn't boast UPF protection and only features two small reflective logos, a critical feature that could make this highly versatile shirt a great choice for urban commuters. Nonetheless, the primary features of this shirt remain in the fabric.

We couldn't smell a hint of our efforts on this versatile shirt. It felt like forgetting to record a run on Strava. Week after week, there was nothing to show or smell. The odor-control benefits of Merino wool are striking. We sniffed for odors while exercising in the shirt, after workouts, and after it had been balled up dirty on the floor and found little to no trace of all our adventures. Impressive.

Should You Buy the Black Diamond Rhythm Tee?

The Merino wool of the Black Diamond Rhythm Tee eliminates odor and offers superior breathability and unparalleled stretch. This shirt is ideal for layering, creating a fit that is excellent for running or as a base layer. For the multi-sport enthusiast or the hundred-mile veteran, this shirt helps with thermoregulation and ventilation and provides a comfortable fit with layers or a pack. The lofty Merino wool is so light that it feels — and smells — like you aren't even wearing it.

What Other Running Shirts Should You Consider?