Chasing records: The Storck Aerfast.5 Pro in the TOUR test
Some time ago, wind tunnel operator Ernst Pfeiffer surmised that high-bred aero bikes could become even faster by five to six watts. The UCI's revised technical regulations had only been official for a year, and two racing bikes fuelled speculation with new records in Pfeiffer's GST wind tunnel on Lake Constance: The Simplon Pride II was the first production bike to break the sound barrier of 200 watts according to the TOUR test protocol, while the Storck Aerfast.4 Pro landed a hair's breadth behind it.
Both manufacturers have already applied the reformed UCI guidelines, which have allowed more aerodynamic tube shapes since 2022 and therefore enable faster racing bikes. Since then, the entire industry has been experimenting with new framesets, exhausting the so-called "Clarification Guide" of the cycling world federation and trying to tease a few watts of power savings out of their competition bikes. The most recent example is the Aerfast.5, the successor to the second-fastest production bike in the TOUR test to date, with which Markus Storck once again set out on a record hunt.
Storck Aerfast.5 Pro: Pure-bred aero bike
The goal of the bustling manufacturer: to break the 200-watt sound barrier at the second attempt and for the Aerfast to claim the unofficial title as the fastest racing bike. To achieve this, Storck and its development department designed a thoroughbred aero racer which, in contrast to the Aerfast.4, pushes the limits of what is permitted and is defined by extremely flat carbon tubes. An aggressive design language, just like Simplon.
"The frame has been completely redesigned. These changes have allowed us to raise the bar even higher," says Storck. While the spectacular fork and the streamlined cockpit have remained unchanged, the head tube has grown significantly in length: the vertical wing measures around 130 millimetres, which, in addition to the optimised tube shapes, junctions and fast wheels, should have a significant influence on the aerodynamics. As a result, the Storck Aerfast.5 aims to be at least as fast as the Pride II, which achieved the previous best value of 199 watts at 45 km/h.
Minimal improvement
Despite the larger tube cross-sections that the UCI has been allowing for two years, the Storck continues to gnaw away at the current record. In the version with only one aero chainring and high carbon rims, the Storck Aerfast.5 comes in at 201 watts according to the TOUR measurement method. With a front derailleur and second chainring, a few watts would be added. Compared to its predecessor, the Bolide improves minimally by 0.6 watts, but the rounded result remains the same. A disappointment? Not at all.
The new Storck continues to achieve a first-class aero value and is almost unrivalled in speed. In fact, the key finding from our exclusive individual test is that the technical innovations within the limits of the UCI regulations only have a nuanced effect on aero performance and that ground-breaking progress is currently hardly possible with conventional means. Or require a further trick, as another measurement in the wind tunnel shows: With narrower handlebars (360 instead of 400 millimetres), the Aerfast.5 would overcome its own air resistance at 45 km/h with a pedalling power of 199 watts. The record of the Pride II, measured with 400 millimetre handlebars and a conventional double chainring, would thus be reached. According to Storck, the Aerfast.5 will also be available in the shop with the ultra-slim handlebar-stem unit.
Storck Aerfast.5 Pro: pure racing machine
Whether the fastest or second-fastest road bike in the TOUR test: the new bike is a pure racing machine and slightly superior to the nominally faster bikes from the Austrian manufacturer outside the wind tunnel. In addition to its excellent aerodynamics, the Storck benefits from a remarkably low weight: compared to its predecessor with almost identical components, it weighs 360 grams less and is even 620 grams lighter than the Simplon. How can that be? "We have used different carbon fibres and also improved the technology of the tools," says Storck. This has made it possible to maintain the weight level of the frame (1113 grams) and fork (476 grams). Compared to the Aerfast.4, the new model also lacks a power meter, while the lightweight Tubolito tubes also help with weight tuning. The rest of the weight is taken up by the seat post, cockpit and the short handlebar tape.
The Aerfast.5 therefore sets best times in many riding situations (see graph below). Overall, the bike craves high speed, can be set in motion with just a few turns of the cranks and effortlessly maintains a speed of over 30 km/h. The very stretched riding position emphasises the competitive nature of the bike, but Storck has more comfortable alternatives in its range for amateur athletes. The frame set, seat post and cockpit - all painted in a bright blue colour - are maximally focused on aerodynamics and require compromises in terms of suspension. Although our test rider pulled out the aero seatpost to the maximum permitted and sat on a high-quality carbon saddle from Selle San Marco, the below-average measured value from the laboratory was confirmed on the road. The front end also reacted stubbornly to unevenness on the top link - the main contact surface for the hands and the measuring point of our new test procedure.
Lively riding behaviour on the Storck Aerfast.5 Pro
In relation to comparable competitors, however, the Storck's low suspension comfort is not exclusive. Other racing bikes are also subject to the dictates of aero and weight optimisation in order to transfer the horsepower to the road as efficiently as possible. The Aerfast.5 achieves this thanks to the stiff frame set; although it leaves room for wider tyres than the narrow 25-millimetre tyres fitted, these in turn would result in minimal losses in aerodynamics.
The lively handling is almost atypical in the aero bike category. The test bike in frame size M, which is positioned between 54 and 56, is particularly favoured by its short wheelbase. While typical representatives are usually a little longer and roll stoically straight ahead, the Storck pants over the tarmac like a young racehorse, waiting for the next turn. This is not always an advantage: on fast descents with wind from different directions, the flat fork offers a lot of contact surface and requires an experienced hand on the handlebars. The tested version is not ideal for mountainous terrain anyway, because the mono chainring and 10-33 cassette offer a limited gear range that is only suitable for professionals or racers with thick thighs. Flat, slightly undulating terrain, on the other hand, can be mastered well with the trendy gear ratio, which has also become popular on road bikes thanks to all-rounder Wout van Aert (Visma-Lease a Bike).
In addition to the tested version, Storck offers two other models with classic 2x12 drivetrains (Shimano Dura-Ace or SRAM Red AXS). In addition to the cockpit, all models can be fitted with high-profile wheels from DT Swiss or Scope. Storck promises a further 400 grams less weight with the wheels from the Dutch manufacturer, which had not yet been released at the time of going to press. This means that the Aerfast.5, available at prices between €10,399 and €11,899, would meet the UCI weight limit and would finally be in a league of its own among aero road bikes. For the time being, even without a quantum leap in the wind tunnel.
Storck Aerfast.5 Pro
- TOUR grade: 2,0
- Price: 10,399 Euro
- Weight: 7.2 kilos
- Frame sizes: XS, S, M, L, XL, XXL (test size greased)
Geometry
- Seat/top/head tube: 498/550/116 millimetres
- Stack/Reach/STR: 537/386 millimetres/1.39
- Stack+/Reach+/STR+: 582/545 millimetres/1.08
- Wheelbase/caster: 980/62 millimetres
Equipment
- Drive/gear shift: SRAM Red AXS (1x12; 50, 10-33 t.) | Grade: 2.0
- Brakes: SRAM Red HRD (160/160 mm) | Grade: 1.5
- Tyres: Continental Grand Prix 5000 25 mm (eff.: 26 mm) | Grade: 1.0
- Impellers: DT Swiss ARC 1100 Dicut 62
- Impeller weights: 1182/1538 grams (v./h.)
Measured values
- Aerodynamics: 201 Watt | Grade: 1.0
- Weight of complete wheel: 7170 grammes | Grade: 2.0
- Driving stability: 7.8 N/mm | Grade: 2.0
- Rear comfort: 294 N/mm | Grade: 4.7
- Comfort front: 96 N/mm | Grade: 4.3
- Ride/ bottom bracket stiffness: 60 N/mm | Grade: 1.0
+ excellent aerodynamics, powerful acceleration
- weak spring comfort, expensive
How TOUR tests
Julian Schultz
Editor
