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review

Syncros Capital SL 40 Wheelset

8
£4,000.00

VERDICT:

8
10
Testament to what is possible when the rule book is torn up
Light
Responsive
Impressive speed
Incredibly expensive
The usual hookless limitations
No ceramic bearings
Weight: 
1,202g

At road.cc every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

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  • Bad
  • Appalling

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.

2024 Syncros Capital SL 40 Wheelset - front hub.jpg

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!

2024 Syncros Capital SL 40 Wheelset - spoke detail 2.jpg

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.

2024 Syncros Capital SL 40 Wheelset - valve.jpg

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.

2024 Syncros Capital SL 40 Wheelset - rear hub 2.jpg

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.

2024 Syncros Capital SL 40 Wheelset - rear hub 1.jpg

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.

2024 Syncros Capital SL 40 Wheelset - spoke detail.jpg

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.

2024 Syncros Capital SL 40 Wheelset - rim detail.jpg

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

road.cc test report

Make and model: Syncros Capital SL 40 Wheelset

Size tested: 700 C

Tell us what the wheel is for and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

Syncros says: "The one-piece carbon design delivers a lighter, stronger and more responsive feel that will make you faster on both road and gravel." They certainly perform exceptionally well, but they're not without their drawbacks.

Tell us some more about the technical aspects of the wheel?

From Syncros:

Range of use: road and gravel

Material: carbon

Rim: One piece carbon fiber, Hookless, 40mm height, 25mm internal width

Nipples: One piece carbon

Spokes: One piece carbon

25 mm inner width/23mm front

Rear hub: DT Swiss EXP 240 custom, DB, 142mm, 12mm TA, CL, XDR

Accessories: Single wheelbag, Tubeless valve 60mm

Diameter: 700c

Wheel axle: TA

Rate the wheel for quality of construction:
 
9/10
Rate the wheel for performance:
 
9/10
Rate the wheel for durability:
 
7/10

See main review: no issues and a generous weight limit, but if you crash and break a spoke then the whole wheel is written off.

Rate the wheel for weight
 
9/10
Rate the wheel for value:
 
5/10

They're not good value but it's easier to see where your money's going than some and the performance is exceptional.

Did the wheels stay true? Any issues with spoke tension?

Perfectly true, spoke tension was good – good job too as there's no way of changing it!

How easy did you find it to fit tyres?

No issues, the tubeless tyres inflated without issue with a track pump.

How did the wheel extras (eg skewers and rim tape) perform?

Ours came with tyres and tubeless valves fitted, no issues.

Tell us how the wheel performed overall when used for its designed purpose

Very well – they're light, spin well, plenty stable enough and surprisingly comfortable.

Tell us what you particularly liked about the wheel

They accelerate phenomenally.

Tell us what you particularly disliked about the wheel

I felt nervous riding them in case I fell off and broke a spoke!

How does the price compare to that of similar products in the market, including ones recently tested on road.cc?

As mentioned in the review, these are some of the most expensive wheels we've ever tested. Compared with the 'similar' Lightweights these actually stack up quite well but they remain an example of paying for diminishing gains.

Did you enjoy using the wheel? 100% yes!

Would you consider buying the wheel? No

Would you recommend the wheel to a friend? No

Use this box to explain your overall score

It's a hard product to score; they're superb wheels with impressively low weight, impressive aerodynamics and a ride experience that is, dare I say, unmatched. Who are they for, though? Who's going to buy a £4k wheelset that is easier to write off than any other? I'm sure there are some people out there who will be happy to take the risk, and if that's you then, overall, they are very good – an 8, that risk tempering a potential 9 – but for most of us they should stay in our dreams.

Overall rating: 8/10

About the tester

Age: 23  Height: 6ft  Weight: 74kg

I usually ride: Specialized venge pro 2019  My best bike is:

I've been riding for: Under 5 years  I ride: Every day  I would class myself as: Expert

I regularly do the following types of riding: road racing, time trialling, cyclo cross, commuting, club rides, sportives, general fitness riding, mtb,

Jamie has been riding bikes since a tender age but really caught the bug for racing and reviewing whilst studying towards a master's in Mechanical engineering at Swansea University. Having graduated, he decided he really quite liked working with bikes and is now a full-time addition to the road.cc team. When not writing about tech news or working on the Youtube channel, you can still find him racing local crits trying to cling on to his cat 2 licence...and missing every break going...

Add new comment

14 comments

Avatar
lesterama | 3 weeks ago
1 like

If I sell my Park Tool truing stand I can afford ten percent of one these front wheels. Result!

Avatar
PRSboy | 3 weeks ago
0 likes

For £4,000 I'm surprised to see only 4 stars for performance and construction.  I'd expect perfection, or close to it.

Avatar
Secret_squirrel | 3 weeks ago
0 likes

Out of interest I've never (yet) broken a spoke, though my annual mileage is pretty low.

Am I an outlier?

If I had this sort of money to waste on wheels I'd be tempted... (Not that I actually have any legitimate use for them).

Avatar
wtjs replied to Secret_squirrel | 3 weeks ago
2 likes

Out of interest I've never (yet) broken a spoke

Many decades ago they used to break all the time, but I haven't broken one for 25 years- even on my present gravel bike. The rims break, but not the spokes

Avatar
lesterama replied to wtjs | 3 weeks ago
0 likes

Same. Broke plenty until around 20 years ago. I've smashed a few wheels out of true since, though.

Avatar
Steve K replied to Secret_squirrel | 3 weeks ago
1 like
Secret_squirrel wrote:

Out of interest I've never (yet) broken a spoke, though my annual mileage is pretty low.

Am I an outlier?

If I had this sort of money to waste on wheels I'd be tempted... (Not that I actually have any legitimate use for them).

I broke two on the same wheel on a multi day trip from London to Sunderland in 2016 - I think the repair on the first was probably botched hence the second.  They are the only broken spokes I have ever suffered.  (I bet break one on the commute home tonight.)  In a similar vein, I've only ever had a chain break on me once.

Avatar
andystow replied to Secret_squirrel | 3 weeks ago
0 likes

I made a forum post on my repeated broken rear spokes on the Trek District I bought new two years ago. That seems to now be sorted after replacing the rear wheel once, then having that replacement rebuilt by hand.

The only other time I've broken spokes was on a 1990s Raleigh hybrid, which was 20 years old when they started to go, and on my Bickerton Portable, which had really bad spoke angles due to the small wheels.

My Hunt wheels in my other forum post cracked around every drive side spoke hole, so the spokes were stronger than the rim.

Avatar
wtjs replied to andystow | 3 weeks ago
1 like

That seems to now be sorted after replacing the rear wheel once, then having that replacement rebuilt by hand

I think all my wheels now (apart from the original front on the gravel bike, which has unaccountably kept going) are now built by Paul Hewitt at Leyland

Avatar
hawkinspeter replied to Secret_squirrel | 3 weeks ago
0 likes
Secret_squirrel wrote:

Out of interest I've never (yet) broken a spoke, though my annual mileage is pretty low.

Am I an outlier?

If I had this sort of money to waste on wheels I'd be tempted... (Not that I actually have any legitimate use for them).

I've broken a few over the years, but mainly on factory built wheels. Even managed to break a front wheel spoke just by braking (disk brake obviously). Wheels that I've built myself don't seem to have the same issue though.

Avatar
hawkinspeter | 3 weeks ago
1 like

When you really don't want to break a spoke.

Sorry, but I'm going to pass on a set of these as I don't like the sound of "each spoke apparently acting like a leaf spring" - I want strong spokes that aren't going to waste energy by moving around and it's surely a myth that spokes provide any meaningful suspension. There's a reason why we don't see wheels like this:

Avatar
levestane replied to hawkinspeter | 3 weeks ago
0 likes

'each spoke' (single) and 'leaf spring' (made of many leaves) seems contradictory. 

Avatar
hawkinspeter replied to levestane | 3 weeks ago
0 likes
levestane wrote:

'each spoke' (single) and 'leaf spring' (made of many leaves) seems contradictory. 

"Acting like", not necessarily "built like". However, I don't think leaf springs work under tension and instead require compression which isn't how spokes usually work.

Avatar
levestane replied to hawkinspeter | 3 weeks ago
1 like
hawkinspeter wrote:

"Acting like", not necessarily "built like". However, I don't think leaf springs work under tension and instead require compression which isn't how spokes usually work.

Agreed on the spokes (tension reduction), leaf springs normally work under bending (sometimes cantilever). 

Avatar
mctrials23 | 3 weeks ago
1 like

Pretty cool to be fair. Insane money but pretty cool. 

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