Ride comfort and better road holding – made possible by SuperPro polyurethane
There are many prejudices against polyurethane in suspension technology today: PU bushes are said to make the ride "hard", cause noise or increased vibration. In truth, however, a distinction has to be made, because not all polyurethane is the same! Depending on its chemical composition, each polyurethane blend has fundamentally different properties. In suspension technology SuperPro uses a very high-quality polyether polyurethane, which, unlike the polyester polyurethane used by other manufacturers, has a fundamentally different chemical structure and therefore different properties.
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Differences between polyurethane materials
The following diagram shows the differences between SuperPro's polyether polyurethane and the polyester polyurethane of other manufacturers:
- Properties of SuperPro polyether polyurethane: As you can see, SuperPro polyether polyurethane has a progressive characteristic. This means that the more force acts on the bush, the more counterforce the bush develops (resilience). With light forces on the bush (e.g. uneven road surfaces) only a small counterforce is produced, so these forces are taken up and absorbed by the bush. In this case the driver travels as comfortably as with the original rubber bushes! However, when the SuperPro bush experiences a strong force (e.g. in fast cornering or on the race track), it reacts with a high restoring force, which leads to direct turn-in behaviour. In short: the SuperPro bush reacts differently depending on the situation. With our products we ensure the comfort of rubber and at the same time the handling of a very hard material.
- Polyester polyurethane material used by many other suspension bush manufacturers: The diagram shows that polyester polyurethane has a fundamentally different character from SuperPro polyether polyurethane. The progressive characteristic is missing here. This material reacts with almost the same force no matter how high the force acting on the bush is. This inevitably results in a harsh ride!
Hardness of the polyurethane material
Many customers ask us about the hardness of the polyurethane material used. There is no general answer to this, because the hardness of each individual bush on a vehicle is tuned by our engineers in extensive driving tests to the force acting at the respective mounting position.
Other manufacturers use the same hardness for all bushes on the vehicle. In our opinion this makes no sense, because a different force acts on each bush in the vehicle. As a rule the most heavily loaded bush is the rear bush of the lower control arm on the front axle. For this bush we usually offer different hardness grades – generally 70 or 80 for the road and 90 Shore for motorsport. This is, however, more a matter of the durability of a harder material under large forces than of better handling. The reason is the progressive characteristic of SuperPro polyurethane, as described in the first section.
The bushes on the rear axle, on the other hand, are far less heavily loaded, so the hardness has to differ from the front axle depending on the position. Only in this way can the same "dynamic" hardness be ensured on the front and rear axle and at all mounting positions.
In addition to the individually tuned hardness grades, the bore in the bush is slightly smaller than the diameter of the tube, so the bush becomes firmer after the tube is pressed in. This is why the curve in the diagram above starts above zero: there is already a small preload that holds the bush firmly in the control arm after the tube is pressed in.
SuperPro avoids NVH (Noise, Vibration, Harshness) through, among other things, the special polyurethane material and individually tuned hardness grades
Through the special material and the hardness grades tuned to each mounting position, we ensure that even when a complete bush kit is fitted, ride comfort matches that of original rubber bushes while the sporty handling matches that of a very hard material.
