Crankbrothers Synthesis Enduro Alloy I9 Wheelset Review



Words by Robert Johnston | Photos by Adam Lievesley

Crank Brothers introduced their Synthesis line of wheelsets in 2019, bringing their “tuned” philosophy to the table. Essentially, Crank Bros determined that the front and rear wheels had different jobs and different needs, so they tailor-made front and rear specific wheels to provide the best performance on each end of the mountain bike or eMTB. A couple of years later, they trickled the Synthesis nomenclature and build approach down to a lower price point, with their Synthesis Enduro Alloy wheelset available with their own-brand hubs or with Industry 9’s 1/1 hubs. We put the latter to the test with a hammering across a range of UK bikeparks and natural tracks. Keep reading to find out how they held up.

Following on from their carbon fiber premium siblings, the Crank Brothers Synthesis Enduro Alloy I9 wheelset aims to offer the same tuned ride feel in a cheaper offering. The front wheel is designed to offer a little more flex to conform to the trail and maximize grip and comfort. The rear wheel is designed to be a stiffer and more durable platform to withstand the rigors of life on the back of the bike, which is typically where the abuse is greater.

Crankbrothers Synthesis Enduro Alloy I9 Wheelset Review

Both rims are produced from a 6013 T6 aluminum alloy, with a welded and sleeved joint to ensure there’s not a weak point on the rim. The front rim features an inner rim width of 31.5mm, whereas the rear is slightly narrower at 29.5mm to offer the optimum level of support for the typical tire sizes on each end of the bike. The rims are quite shallow at 20mm high, which should offer some vertical compliance on the trail.

Further trail compliance is added by the 28 Sapim D-light spokes present on the front wheel. The rear wheel, tuned to be stiffer and stronger, sees this bumped up to 32 spokes of the burlier Sapim Race variety. These are laced into Industry 9’s American-made 1/1 hubs, which feature a six pawl driver that produces 90 POE from a 45 tooth drive ring thanks to the double-phased design. These hubs can be had in Boost spacing with XD, HG or MicroSpline drivers in both 27.5” and 29” sizes, with 29” superboost options too.

The Crank Brothers Synthesis Enduro Alloy I9 wheelset is offered in single wheels only, with the 880g front wheel retailing for $350/£300 and the 1077g rear going for $550/£435. That adds up to a 1957g wheelset that retails for $900 all in.

Crankbrothers Synthesis Enduro Alloy I9 Wheelset Review

The wheelset came on a YT Capra test bike, which ensured it would be put to work on some of the gnarliest terrain in the UK. Through perfect bikepark turns that begged to be attacked and railed, through to rough natural terrain, the Synthesis Enduro Alloy I9 wheelset proved to be simply excellent.

In the world of Enduro wheels, their weight and acceleration is quite average. They’re certainly not a heavy feeling wheelset, but don’t have quite the same “snap” in acceleration or when switching direction as a lighter alternative. As a balance of compromise they feel like an appropriate wheelset to support heavy hitting on enduro trails or in the bikepark without ruining climbing and mellow trail performance, but they likely won’t be the ticket to transforming your bike into an XC whippet.

The wheelset appeared to roll exceptionally fast, regularly pulling away when rolling on a fireroad and spinning for a very long time when in a bike stand. The hubs never skipped a beat throughout testing, with solid engagement that is fast enough to keep all riders happy except for those who demand the instant engagement of the likes of the I9 Hydra or Onyx hubs. Given that they are the “budget” I9 hub, they certainly don’t take away from the performance of the Crank Brothers wheelset.

Crankbrothers Synthesis Enduro Alloy I9 Wheelset Review

The effects of the “Tuned” design approach were quite apparent, with a difference in the reaction of front and rear wheels under certain situations on the trail. The front wheel did feel quite compliant when pushing in hard for a turn, no doubt accentuated by the stiff 38mm fork on the front. That said, though it was clear that the wheel was offering a bit of “give”, it never felt vague or unpredictable nor did it “snap” out of a corner. Through rough terrain there was a little less deflection off angled faces that I’ve come to expect from bikes equipped with the new crop of burly forks, but certainly still that bar-wheel connection that is so reassuring when on the charge. The rear wheel wasn’t “carbon stiff”, but didn’t flex excessively under hard cornering loads on some of the best corners in the country in hero dirt conditions. Reassuring would be the word, feeling plenty stout to take a good beating, but without feeling like anything other than a good alloy enduro wheel.

Throughout testing there were a number of moments riding trails blind, during which I wasn’t holding back. This led to a number of hard impacts to the tire and rim, which suggested they’re not an ultra-tough wheel in terms of dent resistance as I managed to put a few dings in them early on prior to fitting an insert. These dings were not concerning and didn’t compromise the tubeless seal, but were noteworthy, nonetheless. Denting rims seems to be a bit of a lottery, and in this case, I think all the numbers that came up were 13, but the bad luck didn’t lead to any write-offs.

Crankbrothers Synthesis Enduro Alloy I9 Wheelset Review

Through a lot of hard charging and corner slapping they remained true and tight, which was impressive as the Capra they came equipped on saw some of, if not the rowdiest riding I’ve ever done. At 95kg, there’s not too many wheelsets that hold up to my abuse without needing a little TLC, but the Crank Brothers Synthesis Enduro Alloy I9 wheelset did just that. They’re certainly approaching the premium level of aluminum-rimmed wheelsets but offer performance to justify every bit of that premium price tag.

The Wolf’s Last Word

Though they weren’t the first to do it, Crank Brothers’ move to tune each wheel for their discrete requirements led to their Synthesis Enduro Alloy I9 wheelset offering some fantastic performance out on the trail, feeling great and surviving a whole lot of abuse in the process.

Price: $350/£300 (F) | $550/£435 (R)
Weight: 880g (F) + 1077g (R) (29”, microspline, taped)

We Dig

Fast Rolling Hubs
Quick Engagement
Front wheel “give” in rougher terrain
Rear wheel stiffness
Strength and build quality

We Don’t

Rims did dent


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