Review: Middleburn RO1 chainset

The black chainset and crank of a bicycle
Middleburn’s RO1 chainset offers multiple options and engineering excellence – at a price
Cycle magazine’s technical editor Richard Hallett reviews a superbly engineered square-taper chainset from Middleburn with lots of options

Perhaps the only hurdle when considering the purchase of a Middleburn chainset is getting to grips with the generous selection of crank formats, of which there are at least five (excluding ones for tandems).

In part a legacy of the brand’s early involvement in mountain bike components, the range includes external bottom bracket and square-taper options in wide and narrow tread styles. There is something for everyone from fat bike riders to old-school cycle tourists.

If you’re after a narrow Q-factor (pedal tread) and a square-taper axle, the RO1 is the one you want. Like all Middleburn parts the cranks are offered in silver or black finishes, making it easy to assemble a chainset to suit a bike build.

Available in 160, 165, 170, 172.5 and 175mm lengths, the cranks are hot-forged in 7075 T6 aluminium alloy to a shape determined using advanced stress analysis and then CNC-machined where necessary before being hand polished and anodised.

The result is not only visually pleasing but, going by ride feel rather than scientific measurement, commendably stiff when mounted on the recommended 113mm square-taper axle. This gives the standard road double chainline of 44mm. The 148mm pedal tread is also close to the road convention of 150mm.

Choosing a chainring spider is almost as much fun. All the Staffordshire firm’s spiders and right-hand cranks share the same 12-lobed interface with a threaded lockring, so there are near-endless chainring possibilities – including 130mm and 110mm BCD doubles and a four-arm triple option. I choose the RO1 94BCD Double Road spider, which will take a usefully-low 30t inner ring.

There’s a wide range of fittings for this spider, including the specifically paired 11-speed 46-30 rings tested, which run and shift perfectly well with a 10-speed chain. Also available are 8/9- and 9/10-speed rings, some with a hard coat finish. Middleburn’s own black aluminium chainring bolts and self-extractor crank bolts complete the chainset.

Along with Middleburn’s precision engineering, the RO1 has two particularly attractive features: the vast range of chainring sizes, making it ideal for a customised transmission; and the square-taper axle interface. Suitable JIS square-taper, cartridge-bearing bottom bracket assemblies are inexpensive and readily available and offer greater durability than many external bearing designs.


An exhaustive choice of options including, importantly, a square-taper axle fitting, plus engineering and manufacturing excellence make Middleburn chainsets a compelling proposition – albeit at a price.

Other options

Praxis Alba DM-X Chainset £185

A chainset

Price includes a Praxis BB M30 bottom bracket. It’s a versatile, sturdy design with a specific bottom bracket assembly.

Shimano GRX £104.99

A chainset

Gravel-specific chainset with 46-30 rings and four crank lengths. Also available in a 1× format.

First published in Cycle magazine, October/November 2022 issue. All information correct at time of publishing.

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Tech spec

Price: £329.50 (as tested).
Crank lengths: 160mm, 165mm, 170mm, 172.5mm, 175mm.
Available from: Mountain Bike Components.

Pros & cons

+ Wide range of size options
+ Silver or black finishes
+ Superb fit and finish