Syncros Capital SL Reshape Ultralight Aero Monocoque Carbon Wheels for Road & Gravel

Born as an ultralight, super-stiff ultra-premium carbon mountain bike wheel concept, Syncros has adapted their 1-piece molded monocoque full-carbon wheels for drop bars with two new Capital SL wheelsets. Designed to deliver industry-leading lightweight, ride-tuned stiffness, aerodynamic performance, and modern road & gravel versatility the Syncros Capital SL wheels are undeniably expensive, but it’s hard to argue with their performance either…

The Syncros Silverton SL mountain full-carbon monocoque mountain bike wheels were a bit game-changing in their combination of stiffness, lightweight & off-road durability. So, Syncros figured why not adapt that same monocoque tech for road riding too, with extra added aerodynamic benefits too.

These aren’t just narrower, deeper versions of the Silverton though, Syncros completely reshaped the concept for the Capital SL road wheels under a new “System for Speed” guise.

Syncros says the all-new Capital SL wheels are built to be faster than other aero road wheels around 4 key points: low weight & inertia, low aero drag, low rolling resistance, and better handling & riding character.

Low weight is relatively easy to quantify thanks to the full carbon construction, with continuous fibers molded for the spokes from one side of the rim to the other around a carbon hub flange. These even ditch the extra carbon spacer the mountain bike wheels put around the alloy hub shells, as Syncros realized their bonding process made them unnecessary.

Low aero drag is the biggest real difference between the new Capital SLs and the mountain biking Silverton SLs. Syncros optimized aerodynamics in two different rim depths – 40mm or 60mm – based on 3 years of real race wind data collected by team DSM, to get a weighted impact of -20 to +20° yaw angles to find a single weighted drag figure to optimize for real race conditions.

Surprisingly to me, the carbon spokes stick with a mostly flat 2mm thin profile x 4.75mm wide. Durable carbon doesn’t really like the sharp edges that would give you a conventional bladed spoke shape, but the Capital SL’s spokes are slightly aero-shaped smoothly narrowing to 1.5mm thick at their front & rear edges.

Syncros also then had to develop a new motor within a wing to measure rotational drag inside the GST wind tunnel (claiming it to be 27.5% of total aero drag) since previous testing was limited to measuring only translational drag (the wheel moving horizontally through the wind, but not taking into account the effect of aerodynamics on the actual spinning of the wheel). Syncros says the Capital SL Aero has about 15% lower rotational drag than a comparable Zipp 404 Firecrest wheel, thanks to the 1-piece design, optimized spokes, fewer spokes, and no nipples.

In the end the 60mm deep Syncros Capital SL Aero wheels outperformed all of its direct competition. The 40mm Syncros Capital SL was a bit closer, but still faster than its competitors. And in fact, the 40s were pretty much on par or faster than several much deeper wheels, that weigh a lot more, even with the riding benefit of wider tires.

The low rolling resistance came a lot with the choice to use wide hookless internal widths, and to partner with Schwalbe for the development of their faster-than-ever Pro One Aero road tires. Those resulting tires will be exclusive for OEM spec to Scott bikes with Syncros wheels for the next year, but can be bought on their own direct from the German tire maker, too.

Lastly is the hardest-to-quantify ride quality, but we noticed a number of tweaks here that differ from the Silverton SLs to make the Capital SL wheels more forgiving, without sacrificing on ultra-lightweight or unparalleled stiffness. The biggest change besides going to narrower & deeper rims was moving the carbon spoke attachment close to the centerline of the rim. Compared to the MTB wheels which align the spokes with the outside edge of the rim for max stiffness, the Capital SL wheels are able to maintain the stiff ride feel from hub to rim, while allowing the rim itself to slightly flex independent of the ultra-stiff spokes for more of a snappy feel when cornering.

The new wheels are built with the same monocoque carbon tech as the Silverton SLs, making them the only 1-piece carbon-spoked wheels on the market with the spokes actually in tension.

The wheels are laid-up with both hub flanges closer to each other in the mold than they will end up, then spread after they are cured and come out of the mold to bond the DT Swiss hub internals in place.

All of the new Capital SL wheels feature hookless tubeless-ready rims. That will limit what tires are compatible – you can certainly match them to the new Schwalbe Pro One Aero tires that were co-developed with Syncros on these wheels – but Syncros also prints a small QR code directly on the rim next to the valve that takes you to a page to find compatible tires.

The Capital SL Aero wheels feature a narrower 23mm internal width on the front wheel to create a taller, more aerodynamic profile for your front tire, while the 25mm internal rear will ideally make the same tire a bit wider for lower rolling resistance and improved grip. The lower-depth Capital SL wheels share that same 25mm width prioritizing rolling resistance and extra grip, control & rider comfort.

Because of their unique construction, they also have a continuous rim bed with only one hole for the valve, making tubeless setup easy without any tubeless tape needed.

Two different versions of the new top-tier Syncros monocoque carbon road wheels are offered with two different depths – available from September 2023. The deeper 60mm Syncros Capital SL Aero wheels sell for $4200 / 4200€, featuring a narrower 23mm internal front & wider 25mm internal rear wheel for maximum aerodynamic gains and still a claimed wheelset weight of just 1290g.

The shallower 40mm Syncros Capital SL wheels sell for a bit less at $4100 / 4000€, featuring the same 25mm internal width front & rear for versatility, and with an ultralight claimed wheelset weight of only 1170g. Mixed-depth wheelsets are also available.

Both are ostensibly ultralight and aero road wheels, but Syncros assures us that they are actually approved for use either as road or gravel racing wheels. We can’t expect there will be a ton of riders buying 4000€ wheels for their gravel bikes, but their performance claims would be hard to argue with for top-tier gravel racing.

Much more attainable for riders with a budget, there are also conventional steel-spoked Capital wheels coming in September too. Next-tier Capital 1.0s Aero (1470g) & 1.0s (1335g) wheels get the same carbon rim shapes plus DT 240 hubs & Aerolite spokes for 2400/2200€. Then, Capital 1.0 Aero (1630g) & 1.0 (1489g) wheels share those same carbon rims but swap in Syncros hubs & round spokes for 1700/1600€.

All get a 3-year discounted crash replacement program, and reasonable warranties – welcome additions on wheels at these pricepoints.

Syncros.com