Crank Brothers Synthesis i9 wheelset uses a front ‘tracking’ wheel and rear ‘drive’ wheel; different spoke counts, wider front rim and thinner rear rim.

Product Overview

Overall rating:

Score 8

Crank Brothers Synthesis i9 wheelset


Crank Brothers Synthesis i9 wheelset review


Price as reviewed:


The Crank Brothers Synthesis i9 wheelset uses a different tuning, manifested as different spoke counts (28F and 32R), spoke tensioning and also a wider front rim and thinner rear rim. We’ve said before how much sense it makes on the exceptional Crank Brothers Synthesis E11 carbon wheels, but can these premium aluminium models produce the same handling benefits for half the money?

Read more: Best mountain bike wheels in 2021 – aluminium and carbon options

Crank Brothers’ mountain bike wheel philosophy is arguably more advanced than other brands. It essentially treats front and rear wheels individually and tunes their specific ride qualities depending on their differing requirements.

The broader sleeve-joined and welded front rim gives a more squared-off tyre profile, more air volume for damping and extra transverse grip leant over, whereas the skinnier rear encourages faster rolling with a rounded tyre profile that also sharpens directional changes. This translates in a similar way to the camber on a set of skis helping initiate turning, and both decisions prove beneficial in the real world too.

Crank Brothers Synthesis i9

Rear ‘drive’ wheel is specced independently of the front ‘tracking’ hoop

On top of this, fewer front spokes should increase radial compliance – or the ability to absorb impacts with square edges, like thick roots, without feeding back harsh jolts into hands and arms that cause premature tiredness and affect tracking and grip.

The pricier alloy versions here use an Industry Nine 1/1 hub with a snappy four-degree pick-up and a Sapim spoke blend with D-Light front – they’re a (significant) 100g lighter than the cheaper alloy versions we’ve tested before.

The Crank Brothers Synthesis i9 package rides tight with a good zingy feel and the rear tyre profile does seem to have comparatively fast rolling speed and good dynamism. It’s hard to detect, however, much difference from other similar, good quality, front alloy wheels, and Crankbrothers’s aluminium rim doesn’t feel especially soft or resistant to fluttering across stone-flecked surfaces compared to its remarkable carbon sibling. Our guess is that it’s a lot harder to replicate in metal the complicated fibre lay ups and rim depths of the carbon wheels.

This is a snappy, tough-rimmed, quality set of alloy wheels delivering optimised tyre profiles at each end, but otherwise it struggles to stand head and shoulders above the competition when cheaper, lighter and faster- feeling alloy packages are available for a similar price. Your wallet won’t thank you, but splash out on the superb carbon versions if you want the maximum Synthesis advantage.


Weight:900g front + 1,008g rear = 1,980g pair
Internal rim width:31.5mm front, 29mm rear