Syncros Capital SL 40 Wheelset

The Syncros Capital SL wheels have been high up our reviewing wish list for some time, and come with the tagline of 'Ride the future today'. The one-piece carbon construction certainly sets them apart from 'traditional' wheels and if the Capital SLs are anything to go by then the future of road wheels is stable, fast, and insanely light, if rather impractical if you crash, and eye-wateringly expensive.

> Buy now: Syncros Capital SL wheels for £3,514.94 from Lordgun

For slightly more affordable options, check out our guide to the best road bike wheels and the best gravel wheelsets on our sister site off.road.cc.

We've tested all manner of the latest carbon wheelsets here at road.cc, from budget-friendly hoops such as the Velocite Hyperdrive 50s (£699) to bank-breaking beauties such as the Princeton Carbonworks Peak 4550 Evolutions with a staggering price tag of £4,899. Despite their huge variations in price, nearly all of the recent carbon wheels we've tested follow a similar pattern: a wide carbon rim, 20 or so steel spokes and an aluminium hub holding it all together.

The Capital SLs, though, for better or worse, very much go against this trend. Pull them out of the box and you'll be greeted by a one-piece carbon design. Oh yes, the spokes, the rim and even part of the hub is just one piece of carbon fibre.

Syncros says this monocoque design delivers a 'lighter, stronger and more responsive feel that will make you faster on both road and gravel. Faster acceleration, faster cornering, better handling and unreal aero performance is achieved on a wheelset barely tipping the scales'. Just about everywhere then!

I'll start with the easiest claim to verify: the weight. Syncros makes the Capital SL wheels in two variations, the 40mm-deep version that we have here and an Aero model with a deeper, 60mm rim. The 40mm wheelset has a claimed weight of a mere 1,170g, making it one of the lightest wheelsets we've ever tested, and on our Scales of Truth the wheels weren't far off, weighing in at 1,202g with tubeless valves fitted (648g rear, 554g front).

Whichever way you look at it, that's a class-leading weight. Compared to other ~40mm-deep wheelsets we've tested recently, they're only pushed by the more expensive Peak 4550 Evolutions (1,220g). Other premium (£1,500+) 40mm-deep wheelsets such as the DT Swiss ARC 1400 38s (1,360g), Fulcrum Speed 42s (1,420g) and Reserve 4044s (1,435g) give a good indication of just how many grams this futuristic way of creating wheels can save.

Low weight is far from the be-all and end-all, though; in fact, many pro teams and manufacturers are sacrificing weight in the name of aero gains. In truth, the low weight itself is unlikely to make a difference to your performance even on a relatively hilly course – after all, there are far cheaper ways of getting that 150g saving!

The benefit of saving it off your wheels, and in particular near the rims, is a reduction in rotational weight. It's hotly debated whether wheels with lower inertia are measurably faster in the grand scheme of things, but it's undeniable that a light wheelset such as the Capital SL is more responsive to accelerations and FEELS faster.

Out on the road, the wheelset performs just as impressively as it looks. The easiest way to describe it is to imagine how your bike felt when you switched out those floppy stock wheels for a set of carbon wheels... then add another level. My Specialized Tarmac SL7 has never felt tighter or more direct; I hate using wishy-washy words in reviews but I'm struggling to find any other way to put it.

These, as you might expect, feel right at home on an out-of-the-saddle climb or sharp acceleration out of a junction, but how about on the flat? Well, as for the aero performance, road.cc still hasn't bought me a wind tunnel, but on my regular routes these held their own against the best in the business. Many of the wheelsets I've used recently have been 50mm deep but despite a clear correlation between rim depth and aero performance, these didn't clock times any slower.

You can't, of course, tell the aero performance of a wheel just by looking at it but in my mind at least there are clues to back up Syncros' big claims. The hub flanges, for example, are freakishly thin; the spokes are deeper than would be reasonable for any steel spoke; and then there's the fact that there are just 16 of them front and rear, which has surely got to help ward off rotational drag.

The wheels also play nice with wide tyres, as you'd hope for a wheelset that claims to be capable of gravel adventures too. The Capital SLs boast a 23mm internal width at the front, a 25mm inner width at the rear, and 32mm and 33mm external widths respectively. Throughout the testing period I've been using a set of 28mm Schwalbe Pro One Aero tyres although I did also mount a set of Continental GP5000s with little issue.

Hooked or hookless?

One of the recurring topics in our reviews is the hooked vs hookless debate (you can read our feature, What’s the difference between hooked and hookless bike wheels, and which is better for you? for more on this) and it's little surprise that at under 1,200g the Capital SLs belong to the latter category. Make of that what you will, but whichever side of the fence you sit on it's undeniable that there are quite a few red crosses on the tyre compatibility chart and it's impossible to say that's a positive.

The wheels roll on an aluminium hub shell made by DT Swiss, which is kind of shoehorned in between the hub flanges to give the wheels tension. In the rear one, you'll find DT Swiss's latest EXP ratchet system, which we're yet to find fault with, as long as you don't mind plenty of noise.

One curious point is that you won't find ceramic bearings in the hubs. Don't get me wrong, there's nothing wrong with steel bearings, but at this price point you do come to expect the best of the best.

And that brings me to what I see as the biggest negative of the wheels, they're one piece! As you've just read, this has an undeniably impressive effect on the weight, responsiveness and aerodynamics of the wheelset, but this isn't a test lab, these are designed to be used in the real world – a place where accidents happen all too often.

Having abused the wheels for the past few months I am confident in their abilities during 'normal' riding conditions, including gravel; they even have a pretty generous 120kg maximum weight limit. With no spoke nipples or conventional spokes, there's also very little to go wrong – they won't need truing or the spoke nipples replacing, for example. However, would I feel confident racing on a £4,000 pair of wheels which could be written off by a broken spoke? I don't think I would.

Any wheels can get broken, but for me, these take integration too far. I don't see the point in having the fastest wheelset out there if you won't race them in earnest. Even with the tiered crash replacement policy, it's safe to say these will cost an absolute bomb to repair or replace.

Despite looking like they'd rattle you to pieces, the Capital SLs are surprisingly comfortable – the most comfortable carbon-spoked wheelset I've ridden to date, in fact – with each spoke apparently acting like a leaf spring.

Value

There are plenty of positives then, so let's address the elephant in the room – the price. At £4,000 it's impossible to say these are good value, not when there are excellent wheelsets that give away very little in terms of performance for a lot, lot less. Somewhat surprisingly, though, these aren't the most expensive wheels we've ever tested – that title goes to the Princetons mentioned earlier, closely followed by a set of Lightweights.

I'd usually now compare the price of the wheels against some rivals, but the Capital SLs feel like a bit of a unicorn...

Compared with other big-money wheels these more than have the performance to compete, and I do think that they bring something different to the table in a segment full of boring uniformity. As an experiment of what is possible, I think they're an incredible set of wheels and I'm glad to have ridden them, but would I recommend spending your own money on them? In truth, no, I'd tell you to go and get the Syncros Capital 1.0s with replaceable spokes instead.

But do buy them if you want the aero performance of a 50mm wheel, the weight of a 20mm wheel, and the looks of a wheel from 2040.

> Buy now: Syncros Capital SL wheels for £3,514.94 from Lordgun

Verdict

Testament to what is possible when the rule book is torn up