A road bike has to be light and aerodynamic. If the frame is also reasonably comfortable and stable enough to allow you to easily take a clean line into the Alpine pass serpentine at 70 km/h, then you are dealing with a top product of the racing bike genre. But when is a road bike the best in its class? The answer to this question depends not least on the criteria by which a road bike is judged. When TOUR began systematically testing road bikes around 30 years ago, nobody thought that it would one day be a matter of course to measure the aerodynamics of competition bikes in a wind tunnel. Saddle comfort was also not given much attention at first, especially as the measurable differences were hardly worth mentioning at the time. In the 1980s, the unforgettable Hans-Christian Smolik laid the foundations for what later became the first and still the most comprehensive objective test procedure for racing bikes. What the tinkerer and TOUR author achieved back then still has an impact today. Among other things, he developed a method in 1987 that made it possible to measure not only the vertical compliance but also the lateral torsion of a frame. However, he largely left it up to the readers to decide what conclusions could be drawn from the measured values.
New era
That changed seven years later. The two engineers and then technical editors Robert Kühnen and Dirk Zedler were looking for a way to make reproducible statements about the riding behaviour of racing bikes. Their point of view: "Ride tests are all well and good, but to make sensible statements about road bikes, you have to expose them to extreme riding situations, ideally on fast and long downhill sections, at high speeds and on different surfaces," says Robert Kühnen. "And it's also best if several drivers do this so that they can compare their respective experiences. Of course, the effort involved would have gone beyond any financial and personnel limits."
Locksmith work became engineering work. The differences are fundamental and wheels today are worlds better. - Robert Kühnen
So in November 1994, after much thought and some experimentation, Robert Kühnen and Dirk Zedler presented a test rig that measured the torsion of the front triangle in relation to the rear triangle. Not yet foreseeable at the time: TOUR made technical history with this test stand. Robert Kühnen remembers the beginnings of the then revolutionary new approach: "The reactions were mixed. On the one hand, the fact that there were objective criteria for testing was welcomed. Manufacturers were able to adapt to this and react accordingly. Back then, racing bikes were hardly ever developed according to technical criteria. To put it bluntly, putting a few tubes together and soldering them was basically locksmith work. Back then, we were able to show where the real differences lay and thus contributed to bikes changing in the right direction."
The foundation has been laid
The "basic research" of the TOUR technicians at the time was carried out in a gigantic comparative test that is almost impossible to realise today: For the special edition of TOUR Velowerkstatt IV, published in 1995, an impressive 49 framesets made of steel, aluminium, titanium and carbon were put to the test. The test criteria included weight, stiffness in the steering head and bottom bracket, mechanical paint quality and build quality. Grades ranging from "very good" to "insufficient" were awarded for each of these characteristics. The winner at the time was the Quantum Pro aluminium frame from US manufacturer Klein, which the testers hailed as the "champion of all classes", topping the rankings for weight and steering head stiffness. Long after the turn of the millennium, the Quantum Pro was still regarded as the benchmark for what was technically feasible with aluminium in frame construction. At the time, the Trek OCLV 5500 was the best carbon frame and came third in the weight ranking. The frames of the first OCLV generation were not yet very torsionally rigid at the time, but one could guess what potential the material carbon would still offer in frame construction. For the first time in the world of road bikes, there was a test procedure with which the editorial team could record and evaluate the most important technical properties of road bike frames and summarise them in an overall assessment.
A little later, the test was supplemented by an evaluation of the equipment, which also made it possible to classify complete racing bikes. Initially, the frame and equipment were assessed separately and were included in the final result with different weightings. Today, it can be said without false modesty that the TOUR test and its results have had a recognisable influence on the development of the racing bike from a sensitive piece of racing equipment for experienced professionals to a safe piece of sports equipment and vehicle for everyone. Or as Robert Kühnen puts it in a nutshell: "Locksmith work became engineering work. The differences are fundamental and tangible, the bikes today are worlds better: the frames are much lighter, much laterally stiffer, aerodynamically much faster and at the same time much more comfortable. The racing bike has acquired real chassis qualities, made possible by high-quality carbon constructions with direction-dependent stiffness."
Great design cinema
Today, the ideal road bike development process looks like this: Developers set themselves defined and measurable targets for performance in individual categories and then work to fulfil the targets. Robert Kühnen adds: "This is more difficult than you might think, because the road bike is an extremely lightweight product. Compared to a high-end road bike frame, pretty much everything that rides and flies on this planet is overweight. Combining all the required properties with as little weight as possible is great cinema. And only the best can do it." The principle of the integrated design of racing bikes, which takes components and add-on parts into account as "organic" parts of the bike right from the start, is now well established. The trend started gradually after the turn of the millennium. Until then, it was customary to build each bike individually, especially for high-quality racing bikes. TOUR took this into account and has been focussing on the road bike as a complete vehicle since 2015. It is no longer individual components that are assessed, but the most important functions such as brakes and shifting. And 2015 also marked a paradigm shift in the history of the TOUR test in another respect.
Compared to a high-end road bike frame, pretty much everything that rides and flies on this planet is overweight. - Robert Kühnen
Changes and additions to the measurement protocol have been made repeatedly since 1995. In 2007, for example, the test was extended to include comfort measurements on the frame and fork. However, the test did not differentiate between different types of road bike at that time. Race bikes were tested according to the same criteria as marathon bikes. This has also changed since 2015. Since then, test criteria have been based on the purpose for which a road bike was developed. For bikes that are primarily intended for racing, a wind tunnel test has since been a central element of the assessment. Suspension comfort, which is less relevant for well-trained professionals and amateur racers than for amateur athletes, only plays a minor role in the final result for these bikes. For marathon racing bikes, on the other hand, which are primarily developed for amateur athletes, weight and suspension comfort are the most important assessment criteria with equal weighting. The aerodynamics of these bikes are not determined at all because, with a few exceptions, they are not a development goal and, given the purpose of these bikes, are probably irrelevant for the vast majority of cyclists. The same applies to gravel bikes, which are still relatively young but are now firmly established.
In spring 2024, around 30 years after the "test big bang", we have once again adapted our system to current developments. The changes follow the (not new) realisation that the bicycle is now consistently understood as a vehicle and no longer as the sum of its individual parts that can be changed at will. If you like, this closes a circle. Even 30 years ago, our starting point was the realisation that riding a road bike is a game with the forces of physics. The forces flow from the ground via the tyres, wheels, fork and frame, handlebars and seat post or saddle to the rider.
Chain reaction
In this chain, the frame is the weakest link and usually characterises the riding experience. From a physical point of view, we are dealing with a series connection of springs; in this arrangement, the weakest link in the chain dominates the overall impression. This is easy to understand: With a slack tyre, all control is lost, no matter how stiff the frame and fork are. We always measure the latter together in the new set-up - just as they do on the road. This means that every road bike can be measured without exception, regardless of how the fork and frame are integrated. What continues to form the basis of the TOUR grade lists box below on. However, the systematic bike tests were only one branch of the development that we initiated 30 years ago. Time and again, the editorial team also scrutinised technical developments, largely initiated by the editor at the time Dirk Zedlerwho, as an assessor and expert, has been working full-time on bicycle safety for decades. Through the publications in TOUR, we were able to draw the attention of many cyclists to parts or constructions on bicycles and racing bikes that were at the very least annoying, if not dangerous. Responsible manufacturers took this as an opportunity to rethink designs and improve products. Here are a few examples in this article. In 30 years, we have come a long way on the road to safe racing bikes.
The criteria for the TOUR grade
- Weight: Weighed complete bike weight without pedals and accessories, measured in the TOUR laboratory. Includes 25 per cent of the final score across all bike categories.
- Aerodynamics: Measurement in the GST wind tunnel. This is only recorded and graded for competition bikes and is included in the final grade with 25 per cent.
- Riding stability: Measurement of the system stiffness of the frameset in the TOUR laboratory. The proportion of the overall score is a uniform ten per cent across all bike categories.
- Comfort: Comfort stiffness measurement on the test bench in the TOUR laboratory. Handlebar comfort has been introduced as a new criterion, accounting for five per cent of the final score for competition bikes and ten per cent for endurance road bikes and gravel bikes. The comfort measurement on the saddle remains unchanged, accounting for ten per cent of the overall score for competition bikes and 20 per cent for endurance road bikes and gravel bikes.
- Start: bottom bracket stiffness measurement in the TOUR laboratory. The percentage is reduced from ten to five per cent for endurance racing bikes and gravel bikes. For competition road bikes, it remains at ten per cent.
- Equipment: The function of the gears, brakes and tyres each account for five percent of the grade for all categories. The grading is based on component tests and impressions during test rides, but not the price or weight of the parts.
- Maintenance and adjustment: Only graded for endurance road bikes and gravel bikes and accounts for ten per cent of the final grade.
The STW value
TOUR introduced the STW value in 1995. "STW" stands for "Stiffness-to-Weight", i.e. the ratio of steering head stiffness to weight. At the time, a high STW value was an indicator of the design intelligence of a frame. Around the year 2000 - the heyday of aluminium frame construction - STW values of around 70 Newton metres per degree per kilogram (Nm/°/kg) were considered outstanding. When Scott launched the CR1 in 2003, the first series-produced carbon frame under 1000 grams, its 95 Nm/°/kg marked a new record, but this was not to last long. Soon numerous carbon frames cracked the 100 Nm/°/kg mark. However, the more other properties such as aerodynamics and comfort became the focus of developers, the more the STW value lost its significance. It generally no longer plays a role in today's test and evaluation system.
Thomas Musch
Publisher
