Ernst Pfeiffer checks the zero point of his six-component balance once again, then starts the turbine that generates the wind and the motors that set the wheels in motion. The turbine starts up with a muffled whine, and we watch intently through an insulating disc as the TOUR dummy road bike picks up speed. The rear wheel with locked freewheel, driven by the pulley in the floor, sets the chain and thus the cranks in motion. The fibreglass legs of our tester accelerate to more than 90 revolutions per minute. The scales in the floor now record the force exerted by the wind on the test bike. A real cyclist would have to overcome this force as aerodynamic resistance when riding freely in order to maintain their speed - it accounts for around 85 per cent of the total riding resistance at a fast pace.
We are in the GST wind tunnel in Immenstaad, on the Airbus site. The unadorned flat building has served TOUR as a test base for aero tests for two years. Today we are in the wind tunnel with our equipment at the invitation of the Swiss company Swiss Side. Its founders, who actually come from Formula 1 and have only been developing wheels for road bikes for three years, want to prove that their new Hadron 625 wheels are aerodynamically top class. This would be tantamount to a small revolution, as the wheels are said to cost just 999 euros - around half the price of the competition's top aero wheels.
The 808 from Zipp is without doubt one of the fastest wheels that TOUR has ever measured. According to the Swiss company, their own measurements have almost equalled its performance. That sounds almost too good to be true: With a rim height of 80 millimetres, the bulbous Zipps are proven time trial material, while the Hadron 625 with its 62.5 millimetres actually belongs in a different league.
That's why we brought various wheels for comparison testing in the wind tunnel: in addition to the Zipp 808, two very good aero wheels in the 60-millimetre league - Zipp 404 FC and Mavic CXR 60 T. Plus a "normal" standard wheelset: the Ksyrium Elite, which is found in many racing bikes.
Head-to-head race
On the large screen under the ceiling of the control room, a thin blue line begins to crawl from left to right. It represents the drag measured by the scales. Christian Kleiner and James Eddison, aerodynamics specialists at the Sauber Formula 1 team, stare upwards with anticipation. The two engineers have carried out the simulation calculations used to optimise the shape of the rim. A supercomputer in England worked with their data sets for two months. Now we are about to see how the wheels behave in the TOUR test setup.
The drag curve starts at the bottom left (diagonal flow from the left), then soon rises, forms a hill in the centre (wind from the front) and drops again towards the right edge of the wing (wind from the right). After 70 seconds it's all over. We see the typical drag curve of a bike fitted with aero wheels. However, this curve only becomes really meaningful when compared with the reference: In the next test run, Zipp's 808 is fitted to the test bike - in otherwise identical conditions. For a fair comparison, we fitted brand new Continental GP 4000 S tyres in 23 millimetres on each wheel, as the tyre has a significant influence on the aerodynamics of the wheel.
Target narrowly missed
The drag line of the Zipp 808 starts slightly below the line of the Hadrons. At large angles of attack (slow speed, lots of wind from the side), the Zipps are therefore better. Towards the centre of the graph (see top right), however, the curves overlap - and only on a large scale can you still see a tiny advantage for the Zipps. Without further analysis, it is already clear that the Hadron wheels are aerodynamically very good. We carry out a number of further tests with the 60-millimetre aero wheels. Result: The curves of Zipp's 404 FC and Mavic's CXR 60 T are almost identical to those of the Hadron 625. Only the standard Ksyrium Elite wheelset shows a significantly higher resistance in the final measurement, especially in crosswinds.
In our usual TOUR evaluation, in which the individual measurements from all angles of attack are weighted differently, the Zipp 808 wheelset is three watts ahead of the 60-millimetre rims - which in turn have a gap of eleven watts to the Ksyrium wheels. This means that with the Zipp wheels, the racer has to use three watts less power at a speed of 45 km/h than with the new Hadron 625 wheels, for example. And that in turn means that the Hadron wheels are not a new miracle weapon in the battle against the clock, but offer the same aero performance as the best 60-millimetre rims from the established brands - and at less than half the price.
Company founder Jean-Paul Ballard, most recently the engineer responsible for the vehicle concept at the Sauber Formula 1 team, sees his market opportunity in being cheap and good: "I always wondered why racing bike material was so expensive and asked myself whether it was possible to offer good quality at a lower price." With the development expertise of his Formula 1 network, production in Taiwan and a warehouse in England, Ballard believes he has now found a solution. "We rely on lean and largely automated processes in order fulfilment. With just four employees, we believe we can bring up to 20,000 wheels onto the market every year." The wheels are sold directly via the website and via a network of selected dealers that Swiss Side intends to build up.
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Fast in headwinds
The Hadron wheels have not only proven themselves in the wind tunnel: Weeks before the wind tunnel test, a wheelset was available to us for riding tests and measurements in the TOUR laboratory. The Hadron wheels are hybrid wheels. The load-bearing rim is made of aluminium, the aerodynamic casing is made of carbon. This design reduces stress for the manufacturer and the buyer: with welded and precisely turned aluminium flanks, the braking effect is very even and predictable.
The rim width at the brake track is 23 millimetres - for reasons of compatibility with any frame, emphasises Ballard. The carbon cover measures 27 millimetres at its widest point and serves solely to control the airflow. The shape looks like a mixture of Zipp's earlier Toriodal rim shape and the current Firecrest profiles. However, Ballard is keen to point out that the optimisation of the rim was not based on the competition, but exclusively on its own simulation calculations (see interview on the left).
When riding with the Swiss-Side wheels, the sound is immediately noticeable. The carbon panelling makes a clearly audible hiss and amplifies the rolling noise - loud enough to make passers-by turn their heads. You have to like this typical time trial sound. Anyone who prefers a silent bike is unlikely to be happy with the Hadrons.
The sailing impression is solid and fast. Especially in light to medium winds, you have the feeling of being able to sail close to the wind. The crosswind sensitivity is rather low for the height, the feedback in the steering is good-natured. In light gusts or when lorries overtake, you only make small turns. In strong gusts of wind, however, you have to grip the handlebars firmly - but experienced riders will be able to control the bikes even in strong winds. Compared to Zipp's 404 FC, the ride is subjectively a little slower, which may have aerodynamic reasons, but may also be due to the higher mass (1,743 grams) and the slightly narrower rim bed of the Hadrons.
Heavy drivers?
The lateral stiffness of the Hadrons is low, comparable to the Zipp 808 FC. You hardly notice any of this when riding steadily. However, heavy riders with strong pedalling should test whether the wheels are right for them. In any case, the wheels are approved for riders weighing up to 105 kilograms and, according to the manufacturer, have passed fatigue tests with overload. 18 or 24 straight Sapim CX-Ray spokes bind the in-house hubs to the rims. Normal brass nipples, which are tightened with a socket spanner through the drilled rim base, sit under the carbon casing. Servicing is therefore unproblematic and replacement spokes are supplied with the wheels.
The wind tunnel test shows: The Hadron wheels are not quite as fast as we had hoped, but at least they are as good as other good wheels of this height. The aluminium brake track and the attractive price are major plus points. Fast doesn't have to be (very) expensive. By transferring expertise from Formula 1, the newcomer Swiss Side has managed to match the performance of major manufacturers with a small team. The concept of combining engineering expertise from Switzerland with production in Taiwan and lean distribution to keep the price down is reminiscent of Canyon's successful strategy. It will be interesting to see whether Swiss Side succeeds in maintaining its position between Chinese no-name bikes and the established brands. The concept of the four Swiss is definitely an enrichment for the scene.
CONCLUSION Swiss Side is attacking the established wheel manufacturers with a mixture of technology, transparency and a favourable price. The Hadron 625 is aerodynamically on a par with Zipp and Mavic and scores over full carbon wheels with a practical aluminium braking surface. The speed gain compared to a standard system wheel is around 1.5 per cent.
PROFILE SWISS SIDE HADRON
Price 999 Euro
Info www.swissside.com
Spokes v/h 1 8/24 Sapim Cx-Ray
Rim Aluminium with carbon cladding for clincher tyres
Width x height 23 x 62.5 millimetres
Weight front/rear 786/956 grammes
Driver weight limit 105 kilogrammes
Lateral stiffness front/rear 43/32 N/mm
Concentricity < 0.24 millimetre
Rotor Shimano/SRAM; Campagnolo
Scope of delivery Wheel bag, quick release, rim tape, spare spokes
