The new Black Series Corsa is the lightest production bike in the world, at 5.24kg, according to its designer, Andy Wallis.
The Black Series range of bikes and components has long been the ’secret' or 'special projects’ label of engineer and designer Wallis, the owner of Poshbikes.
Wallis says: "Whenever a new frame, wheelset or component was required to outperform the standard item, or a specific bicycle is required for a factory race team, when one was not available from their current line-up, a custom item was created under the Black Series codename."
Over the years, this special project division has amassed a collection of frames and components that have proven themselves for pro riders. Yet they've never been available to the public, until now.
Wallis is readying a complete line-up of Black Series bikes and components, including road, aero, gravel and hardtail XC mountain bikes. There are also bars, stems, seatposts, wheels, hubs and a host of small parts, all under the Black Series name.
This special-edition Corsa tips our scales at an outlandish 5.338kg (size-medium). That’s with standard butyl inner tubes, as the bike was being studio shot when I came across it.
Wallis claims the bike weighs in at 5.241kg in full tubeless trim.
Frame and fork details
The frame is a single monocoque construction made with a complex dual-mould technology. The Corsa frames are all proportional, meaning the diameter of the tubing expands across the sizes. This is intended to ensure the ride is the same from XS to XL sizes.
The geometry is aggressive, with a super-short back end with 405mm chainstays.
The Corsa frame has generous tyre clearances (conservatively 36mm, although it looks greater than that) and a threaded T47 bottom bracket shell.
The head angle is race-bike steep, and the front centre is longer than standard road bike geometry.
Wallis tells me the idea behind the Corsa is to build a classic climber’s race bike, yet one that adds stability on descents with the longer front centre.
The frame and fork are light at 595.7g (unpainted, size medium) and 348g (300mm steerer), respectively. That's impressive for a bike with internal routing and clearance for 36mm tyres. It gives current featherweight bikes such as Scott’s latest Addict RC (640g) and Specialized’s Aethos (585g, size 56cm) a run for their money.
Attention to detail
This Black Series bike, however, cheats the scales further thanks to its build. The 220g (100mm x 42cm) one-piece bar/stem is made in collaboration with German lightweight specialist Schmolke. The internally routed one-piece design bonds the stem piece to the bar. That means the combination is available in any size you could wish for.
The carbon crankset is also a collaboration, with carbon specialist THM, weighing 289g (172.5mm) with a Carbon-Ti chainring at 112g.
Conventional wheels, unconventional weight
The Corsa wheels, which use a conventional 28-spoke build, connect the 280g rims via Sapim CX-Ray spokes, with Black Series' own ultra-light hubset (64g front, 149g rear). The wheels weigh in at a mere 1,081g a pair, including tubeless rim tape.
They’re shod with Tufo’s 220g Comtura Prima tubeless tyres in a rough-road ready 32mm width.
Completing the build is a Corsa seatpost made in collaboration with THM and weighing 85g (27.2x350mm). It's topped with a Black Series Corsa saddle at an astonishingly light 52g. The 27.2mm-diameter post is available as an inline or offset option.
As you might expect from a brand born out of Poshbikes' history, the attention to detail goes further in the pursuit of weight reduction than you’ll see from perhaps any other brand.
Take the Black Series Corsa thru-axles, for example.
These are made from a moulded carbon shaft with a ceramic insert for the hex key slot. They are tipped with a metal-threaded end piece that’s keyed and bonded to the shaft. The weights for the road versions of these axles are an astonishing 17g (rear) and 15g (front).
Even the bottle cage bolts are the lightest available. These carbon fibre bolts are sourced from the aeronautic industry. A set of four M5 x 15mm bolts weighs only 2g.
Availability and pricing
This ‘Ultimate’ SL build will be available from Black Series before the end of the year with an expected retail price of £16,000 / $21,650 / €18,350.
Wallis told me he's confident he could build an even lighter version of the bike at less than 5kg.
