The Flow is Rotor’s premier aero crankset, designed in conjunction with Robbie Ketchell, aerodynamics guru and director of sports science at the Garmin-Sharp team.
Rotor claim a saving of 26.4 seconds over 180km (when averaging 200 watts), which is just shy of 6 seconds over 40km. It’s a small saving for the cost of the cranks, but if you’re a serious time triallist it could prove crucial.
With low drag at the forefront of the design process, the cranks were designed using Computer Fluid Dynamics (CFD), which simulate wind tunnel tests while allowing for individual isolation of speciﬁc areas of the bike.
The crank edges are ovalised but come to a point at the centre – one of many design differences where aero gains are made. The cranks use the 3D+ design found throughout Rotor’s range – they’re made of aluminium and feature three internal holes lengthways to save weight without affecting stiffness. A 30mm axle adds to the overall solid feel.
To allow the BB30 axle to ﬁt into a standard, non-BB30 threaded bottom bracket we had to ﬁt a Rotor BSA30 bottom bracket. You can choose between standard 130mm or compact 110mm BCD (bolt circle diameter) depending on the desired ring size.
The solid, disc-like spider looks aerodynamic and incorporates Rotor’s new Micro Adjust System (MAS), which allows ﬁne-tuning of the position of the elliptical rings to get your individual maximum power output point.
Looking at the overall frontal proﬁle of the Flow chainset (with 53/38 Rotor QXL rings) it’s obvious that, compared with other cranksets, they’re narrower, meaning less mass having to cut through the air. Our 175mm cranks weigh in at 563g (768g with the above rings ﬁtted), so they’re not the lightest, but aero often doesn’t mean featherweight.
Without wind tunnel testing it’s hard to quantify Rotor’s aero claims, but the signs are good: our tester won four 10-mile TTs on them! Most racers will have a power output higher than 200 watts over 40km so should see bigger time savings, and we’ve been impressed with their performance over the last few months.
Aero does seem to come at a premium price – depending on what rings you decide to use in conjunction with the Flow crankset, the overall price could end up higher than other top end chainsets – it’s up to you whether those seconds are worth the cost.
This article was originally published in Cycling Plus magazine, available on Apple Newsstand and Zinio.