Last year, just after the Cirque Series race at Alta, I was sent the all-new Black Diamond Rhythm Tee. The folks at Black Diamond knew my penchant for Merino wool, so we were collectively anxious to get it into the testing fray. After nearly a year of use, it’s time to share my long-term thoughts.

Black Diamond Rhythm Tee Features:

  • Uses NuYarn Wool that’s lighter, stronger and faster-drying Merino Wool
  • Claimed to be the lightest wool shirt on the market
  • Responsible Wool Standard (RWS) Certified
  • Machine washable — yup!
  • Fabric Blend: 57% Nylon, 43% Merino Wool, 95 gsm
  • Fit: Slim (I’d call it short)
  • Weight: 90 grams (large, actual)
  • MSRP: $75
Black Diamond Rhythm Tee Review

You can see the sleeve poking out and the crinkled collar.

Rhythm Tee around town and on the trails

Sometimes, it’s pretty clear the difference between a technical, trail running or hiking shirt and an office shirt and other times it’s not so cut-and-dried. With the Black Diamond Rhythm Tee, you get a Merino wool blend shirt that looks snappy around town, but can also double as a technical tee for any sort of outdoor adventures. I’m a Merino wool fan and love when it’s infused into socks, base layers, hats and shirts, but not all Merino wool blends are the same.

Black Diamond is quite proud of their use of NuYarn wool. In short, it’s made to be lightweight and faster-drying than other Merino blends. The best Merino wool still comes from Australia (not sure why — breeding, climate, etc. — but it does), so NuYarn starts with that. Then, that Merino yarn is woven loosely around a nylon core. We’re talking pretty cool yarn tech at this point, right? Of course, nylon has natural stretch and that loosely-wrapped Merino can subsequently stretch and rebound in ways that other Merino fabrics only dream of. On paper it sounds awesome and in practice it’s pretty awesome too.

Sizing on the Rhythm Tee is small. I’d say it’s definitely not “slim” but just small. I’m 5’11” and 170 lbs and the size large is about right. I’d really like a little more length in the sleeves and hem, but the chest size is just right — not snug and not overly-loose. I’d say the sleeves could be just a touch longer so as to avoid unnecessary armpit hair exposure, but they could also be reduced in their diameter. As it is, they poke outward instead of curving around my not-so-muscular arms. In short… size up on this one.

Black Diamond Rhythm Tee Review

Trail running at sunrise in my all-black ninja suit.

For office duty, the Rhythm Tee is great. It looks awesome with a pair of shorts or jeans and the black color goes with just about anything. I love the subtle horizontal striping that gives it a little more depth. That striping is actually the woven yarn and allows the shirt to stretch a lot horizontally, but less so vertically. It’s like a 3:1 ratio of stretch between the two. That stretch definitely adds to the overall comfort and keeps the shirt from sagging under a hydration pack, for example (it’s all part of the plan).

With cap sleeves, pack straps sit nicely and remain comfortable. Wool isn’t always the softest material and while NuYarn is nice and cozy, it’s still Merino wool and will definitely be scratchier than the Patagonia Capilene Cool Trail Shirt, which is super-duper soft. It’s wool, but not your grandpa’s wool, capiche?

Now, testing the shirt trail running and hiking yielded some good results overall, but it’s not perfect. It holds its shape well and is lightweight, but not nearly as light as Black Diamond claims. I’m getting a respectable 90 grams for a size large on my scale. With that, it does breathe well and dries out pretty quickly (but still not as fast as the latest synthetic shirts). What’s odd is that, for me, the moisture tends to migrate down the back of the shirt towards my backside. Because of that, the back hem tended to remain damp longer than it should. I don’t know if gravity does a number or what, but the tail just stayed damp much longer than there body of the shirt.

Black Diamond Rhythm Tee Trail Running Review

In the direct sun, the black color gets a little toasty.

And, I’ll add that when Merino wool does get saturated, it does tend to drape a little saggily. The above mentioned lack of vertical stretch does help in this regard, but it’s no silver bullet and comes with the Merino territory. Again, it does an admirable job, but for all-out performance, it leaves a little to be desired.

Anti-stink qualities are well-documented with Merino wool and the Rhythm Tee does about an average job in the regard. It doesn’t get putrid, but after a couple of trail runs, it needs a washing in my book.

I’m not going to lie to you and say that I’ve taken extra care of this shirt over the past year, because I haven’t. It’s gotten loaded in with the family’s laundry and likely washed and dried in all kinds of unnatural ways. The only thing that I’ve noticed is that the collar and hem have become a little wrinkled. That’s something I’ve come to accept with other Merino shirts, so it’s not a surprise that it’s happening with the Black Diamond Rhythm Tee.

The Good

  • Stretchy, lightweight Merino wool
  • Looks snappy on or off the trail
  • Washable without worry
  • Still no snags, rips or tears

The Bad

  • Collar and hem get creases in them
  • Dries fast for Merino, but synthetics do beat it
  • Moisture tended to gravitate to my backside
  • Claimed weight of 69 grams is not even close on this one

The Bottom Line: Black Diamond Rhythm Tee

I’m in love with all things Merino and the Black Diamond Rhythm Tee is pretty darn good overall for a Merino active shirt. The cool thing is that it can be worn around town, at the office or at the trail. It’s very light, comfortable and uniquely-stretchy. It doesn’t knock it out of the park as far as breathability goes, but it will stay warmer on colder days than a synthetic layer. The black color isn’t my favorite for hot summers on the trail, but there are other colors on offer, so choose one that suits your typical use.

Buy Now: Available from Black Diamond

About Author

A native of the Pacific Northwest, Jason quickly developed a love for the outdoors and a thing for mountains. That infatuation continues as he founded this site in 1999 -- sharing his love of road biking, mountain biking, trail running and skiing. That passion is channeled into every article or gear review he writes. Utah's Wasatch Mountains are his playground.

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