The Lightest Bike Wheels Use String Spokes: Berd Sparrow Carbon Gravel Wheel Review

When I lifted the Berd Sparrow wheels out of the box, I knew they were something special. They are incredibly light, 1,140 g for the pair, complete with freehub body, valves, and rim tape. The Sparrow was the lightest set of gravel wheels I ever threw tires on, and the brand claims it’s the lightest 25mm internal width production gravel wheel available.

I couldn’t help but pluck the Dyneema string spokes like a guitar. They felt like they were under extreme tension but simultaneously “soft.” I wondered if that would translate to a more forgiving ride or a frighteningly flexible set of hoops.

I mounted the Berd Sparrow Carbon Gravel Wheels on my workhorse gravel bike, a Revel Rover. The wheels survived a dry and extremely dusty Central Texas summer and a wet winter. I didn’t lay a finger on the wheels during the entire 8-month testing period, and I wasn’t nice to them. I rode deliberately to see if the novel spokes had a significant downside.

In short: The Berd Sparrow Carbon Gravel Wheels, first and foremost, are incredibly light. It’s not a marginal difference, as is the case with most cycling components; it’s a huge difference. Accelerating and climbing aboard the Sparrow is wholly different, coming off of other (still light) wheels. And the ride quality is extremely comfortable. But, they are about as un-aero as you can get.

Berd Sparrow Carbon Gravel Wheel Review

First, the String Spokes

It’s impossible to look at or touch the Berd Sparrow wheels without immediately focusing on the unique white spokes.

Berd fashions the spokes out of ultra-high molecular weight polyethylene (UHMWPE), otherwise known as Dyneema or Spectra. Dyneema and Spectra are known for being incredibly light and resistant to stretch, abrasion resistance, and fatigue life.

UHMWPE is also resistant to most solvents. It’s simply an extremely durable material. Berd chose the Dyneema brand of fancy plastic and weaves it into round, stringy spokes.

Dyneema has a claimed strength-to-weight ratio that is five to 12 times greater than steel. This is extremely impressive in the context of a bicycle spoke, as carbon wheels with steel spokes are already extremely light. Berd claims its spoke weighs 2.5 g, or half the weight of a quality steel spoke. This saves about 100-200 g in a complete wheel.

I have used Dyneema in the form of alpine backpacks and tents. I’ve relied on the mentioned material properties to literally keep me alive in very challenging conditions while keeping my climbing load manageable. So, I was already confident in the material before receiving the Berd Sparrow wheels. UHMWPE is also used for parachute cords, which is another testament to its reliability under extreme conditions.

The rim end of the spoke has a metal threaded fitting that Berd glues in place. But it’s also held in place by the squeezing action of the hollow woven spoke when placed under tension — think finger trap. The more tension is placed on the spoke, the harder it grabs the fitting.

Berd explained that the drop of adhesive is mostly to keep the metal end in place when the spoke isn’t under tension. This fitting is compatible with standard 14-gauge spoke nipples.

The hub end of the Berd Dyneema spoke is woven into a loop, making it incompatible with standard hubs. The Berd Talon hubs on the Sparrow wheels have a “hooked” flange that anchors the woven spoke loop.

Berd Talon Hubs

Besides the hooked flange, Berd’s Talon hubs are similar to high-end aluminum hubs. The anodized aluminum shells house 17mm front and 15mm rear aluminum axles. Four sealed bearings in the rear and two in the front keep things spinning. Interchangeable aluminum endcaps ensure compatibility with freehub bodies.

The rear freehub body uses a DT Swiss-style 36-tooth ratchet driver with individual coil springs producing 10-degree engagement. An available 54-tooth ratchet would drastically speed up engagement at the cost of more internal friction.

Berd Sparrow Carbon Gravel Rim

Berd outfits the Sparrow gravel wheels with carbon rims that visibly prioritize low weight above all else.

A very shallow 25mm rim depth combined with a 25mm internal width gives the rims a very “old” and “square” appearance against the deeper, more aerodynamic gravel wheels that are now more common. However, the design priority was minimal weight, and at a mind-bending claimed weight of 265 g per rim, Berd clearly achieved the goal.

Another departure from newer wheels is the semi-hooked sidewalls. This “halfway” tubeless-compatible rim configuration delivers a 70psi maximum pressure rating for a 28mm-wide tire.

A detail to note about these rims is that they are not ETRTO-compliant since semi-hooked rims are not included in the technical guidelines for approval. Berd claims its 70 psi/28 mm limit is conservative based on tire blowoff testing done with Kenda.

All these components produce a verified weight of 640 g for the rear wheel and 500 g for the front, with rim tape, valves, and a Shimano Microspline freehub body. Whoa! 1,140 g for the pair, minus the tires and sealant, is astoundingly light. The Berd Sparrow Carbon Gravel Wheel was the lightest wheel I had tested, regardless of cycling discipline. Surprisingly, Berd’s suggested rider weight limit is 250 pounds.

The Berd Sparrow Carbon Gravel Wheel Ride

The Berd Sparrow wheels sounded, looked, and felt unique just handling them while building up the Revel Rover test rig. But how would they actually ride on dirt? Were they fragile? Would the hubs twist? Are the wheels laterally wimpy? Would they smooth out the terrain like a Cadillac?

I was not kind to the wheels during my test period, and these are my impressions.

Damn, These are Light!

The super-low weight of the Sparrow wheels wasn’t just a number to brag about. I felt it immediately, and it wasn’t marginal or even apparent. It was a hit-you-in-the-gut, drastic difference.

I have to immediately climb up a steep gravel and rain-rutted driveway right out my front door. Some delivery services will not come down when it’s raining because they have gotten stuck on the way out. It’s a stay-on-the-saddle, lowest gears rude punch to the legs.

At the bottom, as soon as the two-track transitioned from flat to uphill, I felt it. The rear wheel rotated around much quicker for the same pedaling pressure than any other of the numerous carbon gravel wheels I’ve tested.

The next, higher-speed, and longer hill bore out even more. Not only did the Sparrow wheels accelerate quicker at the bottom, but the bike literally danced up the hill when I stood up. The lower rotating mass of both wheels, combined with the absolute static weight loss, made my trusty Revel Rover feel like a new bike. I cannot overstate the sensation the lightness of the wheels created.

The low mass of the wheels also significantly impacted the flats at speed. The Berd Sparrow wheels, especially the front, felt extremely flickable. Tight S-turns or sharply cutting an apex on a downhill switchback were much easier and quicker. And standing the bike up after banked turns felt effortless.

Berd Sparrow Compliance

Based on the string spokes’ lack of compression strength, I thought they would be much more compliant. I understood they were still under tension and crossed, but my mind also assumed they would be laterally and torsionally less resistant. I was half-wrong.

The Berd Sparrow wheels indeed provided a sublime ride quality. I wouldn’t describe them as “soft;” I would say they made all sizes of square edges “less square.” Put another way, it felt like I had lower tire pressure but without all the negatives of lower pressure. The wheel took noticeable sharpness out of the hit against an edge, but none of the sidewalls squirm, have an inefficient feel, or demonstrate diminished pinch flat resistance.

At least some of this vertical compliance had to be attributed to the shallow rims.

This edge-reducing effect was most felt when I had to navigate square-edged potholes or small rock ledges in succession at high speed. I didn’t instinctively tighten up as much to resist the rapid-fire series of abrupt jolts. This was especially beneficial to me due to a surgically reconstructed wrist.

Fortunately, the concerns about lack of lateral or torsional rigidity followed physics and not the trick my eyes played on my mind. The Sparrow wheels were laterally and torsionally resistant, making handling just as precise as high-quality steel-spoked carbon wheels. This held true despite Berd’s claim that its woven UHMWPE spokes are slightly less resistant to stretch in comparison to high-end steel spokes

Another hard-to-describe effect of the Berd Sparrow aspects was its “silent” ride over chattery terrain. I’m not sure what contributed more — the slightly stretchy spokes, shallow rim depth, or just the fact that the spokes are not steel — but the wheels were pleasantly planted and rode with less “disturbance” over high-frequency, low-amplitude bumps. Riding over “champagne” gravel was truly extraordinary.

Berd Sparrow Carbon Gravel Wheel Concerns

I did have a few concerns regarding the Berd Sparrow’s unique spokes. First, since Berd spokes are less resistant to stretch compared to steel, I thought maybe they would lose tension quickly. This could potentially put the rim out of true sooner. The Sparrow wheels survived what I deem harsh gravel for the entire test duration, and not once did they even go a speck out of true.

Berd claims that some riders will need to true the wheels after an initial period when the spoke tension creeps due to the inherent stretch of the braided structure. But, after this initial truing, Berd states that the spokes are then done stretching, and truing will be unnecessary or rare. The wheels should be more consistent in tension moving forward than steel spokes.

Like bladed spokes, a special tool is required to hold the metal fitting on the rim end of the Berd spoke to ensure the spoke doesn’t twist with the spoke nipple.

Finally, the hub side of the Berd Dyneema spoke isn’t standard and requires a hooked flange. However, a handful of high-end component brands, like Chris King, Industry Nine, DT Swiss, and Onyx, offer hooked flanges. Berd offers build options that include some of these brands.

The Elephant in the Room: Aerodynamics

Finally, the one thing that is obvious to the gravel racing set is that round profile spokes with shallow rims are undeniably not aerodynamic by today’s standards. Round profiles are the worst at slipping through the air, and there are a lot of spokes in a wheel.

If aero doesn’t matter to you, this is a moot point. But to many, and increasingly so, the growing competitive arm of gravel biking and the related market forces increasingly produce deeper-section, more aerodynamic wheels. The Berd Sparrows were the first set of gravel test wheels in 2 years that didn’t have a rim depth of at least 35+ mm.

Berd doesn’t have any wind-tunnel data on its Sparrow Carbon Gravel Wheels and claims that the flyweight status was the design goal. However, the Minnesota-based brand recently released an aero road wheel. The spokes are the same, but the rims are 62 mm deep. If I look into my personal crystal ball, I’d bet Berd is planning on deeper-section rims for gravel.

The Final Say on the Berd Sparrow Carbon Gravel Wheels

Outside of the lack of aerodynamic efficiency, the Berd Carbon Gravel Wheels look outstanding on paper. The brand’s promises regarding the weight and the compliant ride were 100% true — I haven’t said that many times in the world of hyperbolic cycling product claims.

To add to the almost unbelievable spec is the MSRP. At $2,195, the Sparrow wheels cost half or less than many comparable wheels (albeit with deeper rims). Berd also backs the wheels with a 5-year warranty against defects to the original owner and a $200 crash/damage replacement policy for the same term.

I cannot think of a reason not to try the Berd Sparrow Carbon Gravel Wheel if you are not concerned about aerodynamics. The benefits of the incredibly low weight and comfort afforded by the UHMWPE spokes and design equate to improved enjoyment and fun on your gravel grinds.