In this there is unanimity, and it is that the Kobas MR2 is the germ of the current motorcycles of the MotoGP world championship, which laid the foundations of the dynamics of the competition chassis.
There is a before and after of this motorcycle in the history of motorcycling. Before her it seemed that about almost everything was said. But Antonio Cobas saw it differently. This motorcycle proved who was right, and served as an example and basis for the subsequent development of countless models.
It was never a “closed issue” that of how to make a motorcycle chassis. And yes, of course, tons of paper have been written, as they say, about it. Yes, it is true that there are times in the history of this sport when it seems that everything has already been invented and cannot be improved.
And one of those times when it comes to chassis, surely, would be the 70s. At the end of the 70s, progressive rear suspensions, water-cooled engines, intake and exhaust valves, of various types, for 2T engines, brakes, disco… Even alternative front suspensions: tell the Elf guys, with that 500 that De Cortanze designed and evolved for the World Cup.
Antonio Cobas began working with multi-tubular steel chassis before reaching the double beam
But it seems that the steel tube chassis has displaced the others: stamped sheet metal chassis or those used, for example, by Nimbus, in straight steel plate, are no longer tested. Multitubular, single or double cradle and chrome molybdenum steel, is what works. And that is how Rickman, Harris, Bimota and all those tuners who were born in Europe have built them, because the “Japanese” know how to make engines, but not chassis.
Because how does a motorcycle chassis have to be? Truthfully, it shouldn’t be easy to design correctly. But it is true that since Antonio Cobas worked on it, we are clearer about how it works and how that certain relationship between rigidity and flexibility has to be and that, in addition, the relationship between these two extremes must vary depending on the area of the chassis (not the steering head is the same as the side members or the swingarm anchor) and also depending on the use that is going to be given to the motorcycle. You don’t need the same rigidity in the MotoGP world championship as you do to go on errands in the center of the city.
All these aspects were clear to Antonio Cobas from the beginning of his work with the motorcycles. He had worked on car elements (among others, with that same De Cortanze) but already in the late 70s he began to make motorcycle chassis. The first thing, a steel tubular, with mono but simple rear suspension (Cantilever) that was called Siroko.
The Siroko was his first successful competition motorcycle, with engines from Yamaha TZ, Bultaco, Montesa…
With that multitubular he defines a large part of his theories and his true “genius”: the important thing is how the chassis works, according to him, not the material with which it is made. The Siroko chassis sold well, at the end of the 70s, when there was a “craving” for racing: almost 50 units were delivered, for engines ranging from the classic single-cylinder (Montesa or Bultaco Astro, for example) to the fast ones and more. competitive Yamaha TZ 250 and even 350.
At the beginning of the 1980s, Cobas began his association with Manolo Burillo and Sito Pons. They create a company (Tecomsa) and Antonio starts working with a new idea, while Sito gets his first 250cc World GP with a Siroko TZ. The idea comes from those successful monohulls: OSSA, with the famous Giró GP that the ill-fated Herrero led. Or the Bultaco TSS MK2: the 125 didn’t win and the 250 barely rode, but the 50cc won 4 world championships.
That, without counting the infinity of motorcycles from the 70s that have worked with that idea. But Antonio’s monocoque is different: it is open in the center and is made of aluminium, uniting two very rigid areas with a kind of “U”: the steering head and the swingarm anchorage. Hence, one of the names that the press gave to those first aluminum chassis was that of “inverted U chassis” or “U Cobas”. Later we knew them as “aluminium perimeter”.
The Kobas MR2 had an aluminum inverted U or aluminum perimeter chassis
The motorcycle that debuted that chassis was called MR1. In code «Cobas» the «M» stands for Monocoque and the «R» Rotax. It gave us more problems than we all imagined: now, if you are going to make an aluminum chassis, surely it is easy to find something as silly as what type of aluminum you should use: it is not the same to make window frames than to make airplanes. Neither does the chassis. But in 1981; where did you get that information from? And another problem: today equipment and professionals are available to weld aluminum with ease. At that time, no.
Some of the mechanics who worked on this bike talked about how the material sometimes cracked due to the welds, as it is fragile to vibrations. Even so, the chassis immediately demonstrated its validity and the genius of its creator. The motorcycle, with the Rotax twin-cylinder engine and progressive rear suspension with tie rods, won races in the world championship (Imatra in 1982, the first, with Sito) and a year later Cardús won the Spanish, European and even European championships with it. the famous “Superprestigio” Solo Moto.
A good number of competition motorcycles were born from the genius of Cobas.
The bike evolved into a more perfected Kobas MR2 and served as the basis for the successes that would come later with the JJ Cobas -bikes that you can see at the Made In Spain Motorcycle Museum-, such as the 1989 World Cup. But its importance is not Its record: it is to have been the motorcycle that foreshadowed the way in which our sports bikes have been since then and the way in which designers make chassis.
You can admire the Kobas MR2 in the Alcalá de Henares motorcycle museum, in the Motos Made In Spain exhibition.
Text: Dani Navarro
