Extending the magic triangle

Rolling resistance, wet grip and wear resistance form the so-called Magic Triangle of tire performance. But why was it called "Magic Triangle"? When carbon black was the only reinforcing filler in tires the golden rule said that you could not extend one corner of the triangle, meaning improving one of three tire properties, without losing in one of the other two.

For a long time the tire industry aims primarily to make continuous developments in the following fields:

  • Improved rolling resistance for lower fuel consumption
  • Improved dry and wet grip to increase the driving safety
  • Improved tire wear resistance to increase the mileage or tire lifetime

This changed when the so-called "Green Tire" technology revolutionized the tire market. Suddenly two corners, fuel consumption and wet grip, were improved at the same time and surprisingly to a very significant proportion, too. And this was achieved keeping the wear resistance at the current level.

The cornerstone of the “Green Tire” technology is the Silica/Silane-system. It all started with Si 69® which made it possible to use silica in tires and which is still the benchmark worldwide. In contrast to carbon black, which has a high affinity but only physical interactions to the polymers the Silica/Silane-system chemically links the silica filler to the polymer. This chemical link between filler and polymer is created by the functional silane like Si 69® and provides the basis for the unique property profile of the Silica/Silane-filler system.

The excellent tensile strength shows the reinforcing effect of the Silica/Silane-system in rubber compounds.



Compared to tires with carbon black filled tread compounds Si 69® improves the rolling resistance by about 30 % (fuel consumption by about 5 %). Remarkable is that this is achieved by only changing the tread compound which is in contact to the road. In the future further improvements can be expected when the Silica/Silane-system is extended to other tire compounds.

Si 363® is pushing the boundaries even further. Compared to the established Silica/Silane-systems the rolling resistance of tires with Si 363® is further reduced by more than 15 %. Compared to carbon black the rolling resistance drops by about 35 %!


Driving safety is an important element of a tire’s performance. It is expected that the breaking car stops within a few meters even on wet roads. The only contact to the street is made by the tires. Therefore, the tire tread plays the major role. The scientific basics of the wet braking phenomenon are still under investigation, but introduction of the Silica/Silane-system has led to a remarkable improvement of wet breaking. One explanation for the improvement is that in contrast to the non-polar carbon black, silica containing rubber compounds can easilier penetrate the water film on the road surface. Only the unique viscoelastic properties of silica-filled rubber compounds make it possible to match the stringent safety requirements of modern passenger car tire treads.

Rubber silanes are here also key ingredients. Only with silanes like Si 69® the balance between wet grip, wear and rolling resistance is guaranteed.


In Europe, driving safety and fuel efficiency are dominating parameters of a car tire. This is reflected in the European tire lable, where rolling resistance, wet breaking distance are rated together with the tire noise. Wear resistance cannot be neglected in the competitive environment of the tire industry, especially as other regions of the world may lay the emphasis on tire lifetime.

The silane is essential for the wear resistance of silica tires as it links the silica chemically to the polymer. Thus, high energetic bonds between filler and rubber prevent the simple chipping of the silica under stress. The abrasion resistance is improved.

Especially in conjunction with highly dispersible silicas like ULTRASIL® 7000 GR the stringent requirements of modern passenger car tire treads can be matched.


Silica for green tires