A road bike has to be light and aerodynamic. If the frame is also reasonably comfortable and stable enough to keep the bike stubbornly on track even at 70 km/h, then - as all road cyclists can agree - you are dealing with a top product of the road 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 recording and evaluating racing bikes just over 25 years ago, nobody thought that it would one day be a matter of course to measure the aerodynamics of competition racing bikes in a wind tunnel. No particular attention was initially paid to comfort either, and 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 road bikes. As a TOUR columnist and author of numerous specialised books on bicycle technology, he carried out fundamental research that still has an impact today. Among other things, in 1987 he developed a method that made it possible to measure not only the vertical compliance but also the lateral torsion of a frame - as a measure of directional stability and flutter tendency. However, he largely left it up to the reader to draw conclusions from the measured values.
That changed seven years later. In TOUR 11/1994, the two engineers and then technical editors Robert Kühnen and Dirk Zedler presented a test stand that measured the twisting of the front frame in relation to the rear triangle. Not yet foreseeable at the time: TOUR made technical history with this test stand. Even today, many road bike manufacturers use precisely this measuring method to determine the riding stability of their frames. For the TOUR special issue "Velowerkstatt 4 - Frame", published in 1995, 49 framesets made of steel, aluminium, titanium and carbon were put to the test in a large-scale comparative test. In addition to weight and stiffness in the steering head and bottom bracket, the test criteria also included mechanical paint quality and build quality. Grades ranging from "very good" to "insufficient" were awarded for each of these characteristics.
The lone winner is the Quantum Pro aluminium frame from US manufacturer Klein, which the testers dubbed the "champion of all classes", topping the rankings for weight and steering head stiffness. Long after the turn of the millennium, and in fact to this day, the Quantum Pro is still regarded as the benchmark for what is technically feasible with aluminium in frame construction. As the best carbon frame, the Trek OCLV 5500 came third in the weight ranking in the same test. The frames of the first OCLV generation were not yet very torsionally rigid at the time, but it was already clear 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 features 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 road bikes. Initially, the frame and equipment were assessed separately and were included in the final result with different weightings. This was mainly for historical reasons. For a very long time, it was customary to build each bike individually, especially for high-quality racing bikes. It was only after the turn of the millennium that manufacturers gradually began to include not only the frame, but also other components and add-on parts - keyword system integration - in the design. For modern racing bikes, a separate assessment of frame and equipment would therefore no longer be up-to-date.
TOUR took this into account and has been focussing on the road bike as a complete vehicle since 2015. Since then, the most important functions such as braking and shifting have been assessed rather than individual components. This year also marked a paradigm shift in the history of the TOUR test in another respect. Since 1995, there have been repeated changes and additions to the measurement protocol; in 2007, for example, the test was expanded to include comfort measurements on the frame and fork. However, one thing has always remained the same in the first 20 years of the test procedure: a road bike is a road bike. The test does not differentiate between different types of road bikes. Competition racers are tested with the same measuring equipment 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 been mandatory since then. 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 riders, 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.
It would be an interesting experiment to measure the S-Works Tarmac SL7 from Specialized and the Canyon Aeroad CFR, both of which can be considered the best competition bikes on the market for the time being since the test in this issue of TOUR (from page 28), against the instruments of 1995. Both bikes would have received top marks for weight and stiffness back then too. However, other qualities such as the outstanding aerodynamics of the Aeroad or the formidable suspension comfort of the Tarmac would have fallen by the wayside. The enormous technical development that the road bike has undergone over the past 25 years could not be reflected in the test from back then. The reverse is not true. If the TOUR testers were to come across a bike like Klein's Quantum Pro today, the test letter would probably contain words and phrases such as "rock hard" and "aerodynamics of a wall unit". The best racing bike from 1995 is therefore still a welcome youngtimer today. But no longer.
Legendary: 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 weighing less than 1,000 grams, its 95 Nm/°/kg marked a new record, although this was not to last long. Soon numerous carbon frames cracked the 100 Nm/°/kg mark. The current record holder is the Cervélo RCA from 2015 (pictured above) with an STW of 142 Nm/°/kg. However, the more other properties such as aerodynamics and comfort became the focus of developers, the more the STW value lost its significance. As a result, TOUR now only rarely displays it, for example when a frame stands out with a particularly high STW value.
Note: This article appeared in TOUR 11/2020
