Spectrum: Bicycle tires - optically often inconspicuous, they play a crucial role in the truest sense of the word, when it comes to good performance on the bike. We had the opportunity to take a look behind the scenes of tire development at Specialized - in Hessen we met the so-called tire laboratory, those who know what's behind the black rubber facade of the Californian manufacturer's tires.
A tire is a tire is a tire is a tire? Not quite!
They are all black and round. This statement - as superficial as it may be - certainly strikes a chord. Because this is probably one of the reasons why a bicycle tire hardly has the same emotional significance for a cyclist as, for example, a crank or a stem. And that despite the fact that the right tire has one of the greatest influences on driving behavior of all wheel components.
However, there is a lot more behind the mostly inconspicuous exterior of a tire than meets the eye. It is the interplay between the rubber compound, carcass and profile that ultimately determines how well a tire performs in practice. The development is a complex process, for which not only the appropriate technical know-how, but also experience and last but not least practical tests play a decisive role. "How well a tire works can only be determined at the end of the day on the track, the road or the trail." one of the Specialized tire bakers knows from his many years of experience.
But the journey of a tire from paper or from the developers' minds to the rim is long and arduous. This is one of the reasons why Specialized recently decided to concentrate the entire tire development in one place - the choice fell on Germany. “The infrastructure here is simply one of the best. Suppliers are in the immediate vicinity, there are test options and the distances are all very short." explains Wolf vorm Walde, who until recently had his professional home at Specialized's Californian headquarters and is now part of the three-person tire competence team in Germany.
As he talks with a twinkle in his eye about juggling the right ingredients for the perfect rubber compound, paying attention to the correct temperatures and then eagerly awaiting the testers' verdict, you don't have to have a fertile imagination or a fondness for have daring metaphors to be reminded of a bakery or pastry shop. And like the cake, the dough – excuse me – the gum mixture is probably the most important part of the maturing process.
The right mixture - well-kept secret of rubber gourmets
How is a rubber compound actually made? What's in it and who decides which 'ingredients' are used? At Specialized, today's tire recipes have grown out of the developers' wealth of experience and knowledge. A rubber compound (as it is called in technical jargon) always consists of a large number of polymers, which then give the mixture its corresponding properties. Be it the hardness, the grip, the behavior in the wet and/or cold, the abrasion or the robustness - all these factors can be decisively influenced by the appropriate combination of the rubber components.
But despite all experience, it would be economic hara-kiri to rely solely on this and 'bake' the compound for tens of thousands of tires straight away. In order to find the right mix, numerous test phases with smaller 'batches' – i.e. quantities – are necessary. Here we come to the tire laboratory, which we visit here in Hesse. The developers have access to modern equipment on site, with the help of which they can prepare the mixtures for small quantities directly. The polymers are heated, mixed over rollers and formed into a homogeneous mass. Here, too, there are inevitable associations with baking: not only the ingredients, but also 'baking time' and temperature are decisive factors.
When the compound is finally finished, it still has to go through a few dry tests before it is made into a real tire together with the carcass. These dry tests allow certain conclusions to be drawn about cushioning, grip and other properties. If these are promising, the rubber compound goes to Thailand, where a small set of test tires is then produced exclusively for Specialized in a large tire factory. "If it has to be really quick, we'll pack the black block in a suitcase and fly over," says Wolf. But the process also goes very quickly by regular mail. "Two weeks" he estimates that it takes a long time from the 'baking mix' to holding the finished test tires in his hands.
The decision as to whether a tire or a compound will work is made in practice. "No theoretical value and no laboratory test can replace practice," says wolf. At Specialized, the tires go through several test phases. First, the brand-new tires come to the in-house and self-designed test bench in Hesse. Here the rolling resistance is precisely determined and compared. The tires also have to prove themselves in terms of durability and puncture protection. Then a few test drivers - amateurs, ambitious hobby drivers and other frequent drivers - get the test tires. Only when they classify the tire as suitable does the next phase follow - that's when it's the professionals' turn. As is well known, Specialized equips numerous professional teams, three WorldTour teams alone rely on bikes and components from the Californian manufacturer and also in the MTB sector many riders and teams rely on the tires from the laboratory of Wolf and Co. "Then I'll spend a day with Tony [Martin, editor's note]. Editor] on the track to test the new tires", he chatters out of the sewing box.
The Specialized tire team then tries to implement the feedback from these test riders, be they professionals or hobby athletes, as best they can. But you can imagine how difficult it is to implement wishes such as 'The tires tend to wear out quickly in fast corners' or 'a little more grip on greasy roads would be great' given the multitude of factors involved. In addition to the rubber compound, the carcass, profile, tire dimensions and other components also play a decisive role.
The dough is ready! Time for icing, shaping and cream: From the rubber compound to the finished tire
Assuming we have a finished and satisfactory rubber compound at the end: With most tire manufacturers, the corresponding polymer recipe then goes to one of the large tire factories in Asia, where the rubber compound is then first produced, provided with the appropriate profile and married to the carcass. In the past, this production process also applied to Specialized. But last year there was a small but crucial change.
The problem lies in the fact already mentioned at the beginning that tires are all round and black. As a manufacturer, you don't always know with complete certainty what will happen to the recipe that you have developed in a lengthy testing process and then hand over. The big factories produce for many different manufacturers and, as in every industry, the competition is fierce - that's why you don't want to let Specialized look at your cards in the future. This has enabled the rubber compound to be produced in a separate factory in Asia as well. This manufactures rubber for a wide variety of areas, from refrigerators to airplanes. The black rubber gold then goes to the tire factory, where they then produce the finished product without knowing what the composition of the black mass is.
Together with carcass and profile, a complex overall system is created that can only be viewed and changed in its entirety. For example, if you rely on a very soft rubber compound with a lot of grip, you should avoid high side lugs, otherwise they buckle in the corners and lead to spongy handling. The carcass is similar.
An additional challenge are the numerous tire dimensions, which are now mainly found in the mountain bike sector. A tire that works as a 2,25″ 29″ tire will most likely fail in this composition as a 650b+ (or 6Fattie as Specialized calls it) or fat bike tires. So it means for Wolf and co. again: The juggling with polymers, profile and carcass starts (almost) all over again.