The diagonal-tyre has just been overcome, when in 1970, the development of the wide-tyres started. As far as the chassis and suspension are concerned, the simultaneous increase in the rim-diameter, was perhaps even more important. In the case of the brakes, the advantage was two-fold, if the rim is larger, then larger and better ventilated brake-discs can be installed.
This was the time when they were starting to offer various wheel sizes as optional extras, it is still being done today, of course, in addition to the choice between steel- and light-alloy wheels. In the beginning, there wasn't yet the mudguard compensation for narrower tyres, which nearly always made the cheapest versions look a bit like the poor relative in the family.
Now of course, wider tyres can cause problems with the gearbox and the possible speedometer adjustment. This favours the creation of varying height to width ratios, also called cross-sections. The tyres which originally had a ratio of 80% height to width, now were only 70%, and that's when the development really took off. At the turn of the millennium this was finally stopped, when the height amounted to only 25% of the width.
Should a particular car-model present an extensive range of wider-tyres, then the buyer of the standard model is out of luck, because he/she has to resign themselves to having a car with enormous wheel housings. Pretty soon there will only be emergency spare-wheels, which at least, create a little more room. In the meantime the spare-wheels have also given way to the repair sets. Which is a good idea, since tyre defects and the people who can change a wheel themselves, have become quite rare. Since the 1980s, we've been concerning ourselves with the subject of safety when punctures occur. Dunlop had, at the time of his invention, experimented with the wooden (emergency) disc and the storage of compressed air. The company of the same name, has now brought out the Denovo- or Denloc- concept (Jaguar). Continental is working on completely turning away from tyres and the drop-centre principle. This subject is still with us today. 07/14