Crankbrothers Synthesis XCT 11 Carbon mountain bike wheelset review

Crankbrothers’ Synthesis XCT 11 Carbon wheels feature specific front and rear designs to tune the feel to your requirements; the front is compliant and the rear stiff, defined by rim width and spoke count.

As one of Crankbrothers' lightest (1,570g – 29in, Boost 110 and 148mm axle spacing, XD driver, six-bolt disc pattern) and most expensive wheels (£2,250 / $2,400), this model is designed specifically for cross-country and trail riding.

The carbon rims are built to Industry Nine Hydra hubs with a 0.52-degree engagement angle.

On the trail, they’re remarkably supple and smooth, insulating you from feedback. There’s plenty of grip and control on tap, too.

Push very hard in turns and there’s some unwanted flex, but that’s not surprising given their cross-country (XC) credentials.

If you’re not on a budget and want XC-light wheels with trail bike performance, the Synthesis XCT 11 Carbon wheelset will not disappoint – unless you’re a particularly heavy or hard rider.

Crankbrothers Synthesis XCT 11 Carbon wheelset details and specifications

The front rim is 26mm wide internally (measured) and uses 28 spokes. It's designed to create a 'compliant' feel, improving grip and control.

The 26mm figure is claimed to create a wider front-tyre profile to increase volume and its contact patch, while rounding the tyre to “enhance turning”.

Tuned for stiffness, the rear wheel ups the spoke count to 32, but reduces internal width to 24mm (measured) in a bid to increase strength and resistance against loads.

The narrower width makes the tyre’s profile decrease in width, but also should “sharpen [its] edge[s] for grip,” according to Crankbrothers.

While both wheels share their 10mm (measured) internal depth, their external depths (measured at 32mm for the front and 30mm for the rear) and sidewall widths (2.3mm for the front, 2.5mm for the rear) differ.

Both rims are tubeless-compatible and have a lifetime guarantee.

They’re laced to USA-made Industry Nine Hydra hubs – with a quick-engaging 0.52-degree freehub – using Sapim CX-Ray J-bend bladed spokes.

The Hydra’s freehub is easily swapped out and HG, Microspline and XD are all available.

Only 29in wheel diameters are available and my 29in Boost 110 front, 148 rear XD driver six-bolt hub test wheels weigh 1,570g (700g front, 870g rear).

Crankbrothers Synthesis XCT 11 Carbon wheelset performance

Setup and tubeless inflation

Tyres are easy to fit without tyre levers if the bead is pushed into the centre of the rim’s bed.

Both front and rear tyres inflated and seated using just a high-volume track pump, popping onto the rim’s edge with a loud bang at 17psi.

No air was lost during the test period and the factory-installed tape has proven to be very robust; these wheels had been tested for over a year on a colleague’s bike before I got my hands on them.

On-trail feel

Both front and rear wheels feel impressively smooth on high-frequency, small-amplitude trail buzz, doing an impressive job of insulating you from unwanted feedback.

You can sense the wheels reacting to deflection inputs, feeling malleable and forgiving as they make it easier to hunt out grip on rough off-cambers or through turns.

Feeling novel but also brilliant on the trail, it creates a calm and muted ride where control and predictability are at the forefront.

Loading them up into a turn generates a corresponding pop as you unweight the bike; there’s an element of playfulness to their build, accentuated by their light weight.

Push them further – on steep, technical descents or high-load berms – and some unwanted flex is present. While not ruinous for steering accuracy, the limits of these XC-focused wheels are relatively easy to find.

Except for the hub – that emits a brilliant-sounding high-pitched buzz and has lightning-quick engagement – they run quietly.

Heavy deflection doesn’t cause the spokes to bang, ping or twang as they cycle in and out of tension, and the rims don’t dong on hard bottom-outs.

Both the front and rear tyre profiles are pleasantly rounded, helping to improve leant-over side-knob transition grip and predictability.

However, the rear is more rounded than the front; I’d prefer the rounder-shaped tyre profile on the front to improve steering grip, and the blockier, squarer one on the rear for better braking traction and more carcass stability.

That said, at 26mm (front) and 24mm (rear) wide, they’re narrower than most mountain bike wheels on the market.

Once again, pushing the wheels beyond their XC-cum-trail limits can reveal plenty of carcass deformation. High loads frequently burped the rear tyre and deformed the front’s carcass.

Increase tyre pressures to 32psi, both front and rear, and burping reduces, but then grip and comfort is compromised.

Of course, a tyre with a heavier-weight casing wouldn’t suffer the same plight, but it would deceive the principle of lightweight wheels.

While touted for trail riding, the XCT 11s are better suited to cross-country, or lighter riders who push the limits.

Heavier or harder riders might come away looking for a more robust tyre-to-rim connection.

For improved tyre stability, such riders should consider the Synthesis Enduro wheels instead.

How do the Crankbrothers Synthesis XCT 11 Carbon wheels compare to the Reynolds Blacklabel 329 Trail Pro and FFWD Outlaw?

If you’re seeking a forgiving ride, and can stomach the £2,000 asking price, the Synthesis XCT 11 Carbon wheels are guaranteed performers. The Hydra hub is seriously impressive, and the wheels are smooth and damped.

Heavier riders or harder chargers might want to look at the stiffer, marginally heavier (1,620g) and slightly cheaper (£2,250) Reynolds 329.

Although constructed from carbon, the deeper rim profile (38mm versus 32mm on the front, 30mm for the rear) and generous width create a much more robust ride, and a better anchor point for tyres.

FFWD’s Outlaw wheels sit in the middle in terms of feel; they’re both comfortable and damped, but don’t flex as much under higher loads.

They also suffer from tyre-carcass deformation, like the Synthesis, despite being wider. Costing £1,349 and weighing 1,580g, they’re only 10g heavier than the Synthesis and way more affordable.

Crankbrothers Synthesis XCT 11 Carbon wheelset bottom line

Justifying the expense is the Synthesis’ ride-feel. Smooth, compliant and well-damped, there’s nothing unpredictable about them.

Generating masses of grip, it’s possible to rattle down most trails in total comfort.

The Hydra hubs sound brilliant, pick up quickly and are reliable, too.

However, heavier or harder riders might struggle with too much flex when the rims are pushed beyond their XC and trail remit, and the cost is eye-watering.

If that’s not a problem for you, there’s little reason to look elsewhere.