A running-gear silent block withstands continuous impacts, twisting and vibration, so a rubber bushing on a truck or on special machinery often lasts only a few months: the rubber cracks, delaminates from the sleeve, the suspension starts to knock. Every replacement means machine downtime and labour costs. A polyurethane silent block works far longer in the same assembly because it resists wear and is not afraid of oil or frost. This article explains why suspension bushings are worth making from cast polyurethane and how to order them to size.
Why polyurethane is displacing rubber in silent blocks
Polyurethane beats rubber in three parameters critical to suspension: wear resistance, dimensional stability and oil resistance. A rubber silent block loses its elasticity over time, cracks under the action of ultraviolet light and moisture, and swells from oil. Polyurethane keeps its resilience, returns to its original shape after deformation and does not react to technical fluids, so the assembly holds its set characteristics longer.
The main difference lies in resistance to abrasion. Constant micro-movement of the bushing in the sleeve gradually wears the working surface, and this is where polyurethane gives the gain. Per DIN 53516 its abrasion is 38-39 mm³ versus 80-150 mm³ for NBR nitrile rubber. Under the same conditions rubber wears several times faster, and therefore the silent block has to be replaced more often.
Another practical point is the temperature range. Polyurethane works from -60 to +100 °C, whereas ordinary SBR rubber is limited to a range from -40 to +80 °C. This removes the question of a part cracking in the frost, which is often attributed to polyurethane because of poor-quality cheap imitations.
Comparison of polyurethane and rubber for silent blocks
The table sets cast polyurethane against NBR nitrile rubber, which is most often used in assemblies that contact oils. The reference numbers are taken from standard materials-science sources (DIN 53516, ISO 37).
| Characteristic | TIMOL polyurethane | NBR rubber |
|---|---|---|
| Abrasion DIN 53516, mm³ | 38-39 | 80-150 |
| Operating temperature, °C | -60…+100 | -30…+100 |
| Tensile strength, MPa | 39-87 | 10-25 |
| Tear resistance, kN/m | 40-120 | 10-50 |
| Shore hardness | 85A-95A | 40A-90A |
| Rebound elasticity, % | 34-61 | 20-45 |
| Oil resistance | excellent | good |
The most telling rows are abrasion and strength. Polyurethane wears 2-4 times slower than nitrile rubber, and its tensile strength (39-87 MPa versus 10-25 MPa) and tear resistance (40-120 kN/m versus 10-50 kN/m) are several times higher. This directly translates into service life: the silent block holds its seat longer and does not break down at the edges. A wider temperature range at the low end (-60 versus -30 °C) additionally broadens the operating conditions.
Engineer’s tip: for heavy and haulage machinery, take polyurethane with a hardness of 85-95 Shore A, it fixes the suspension more rigidly and holds the geometry more precisely than soft rubber. Before pressing in, prepare the seating bore of the sleeve: clean it of corrosion and burrs and apply a silicone-based assembly lubricant. This eases installation and prevents the bushing from turning under load.
Where polyurethane silent blocks are used
The main field is the running gear of vehicles, where the assembly undergoes constant impact and vibration loads. Polyurethane bushings and silent blocks are fitted on heavy, haulage and agricultural machinery, where reliability matters more than maximum ride softness. A stiffer suspension is even useful on such machinery: the vehicle is more stable under load and holds the road better.
Beyond automotive applications, polyurethane articulated elements work in industrial mechanisms as dampers and vibration absorbers. They take dynamic load off metal assemblies, reduce noise in the workshop and extend the service life of equipment. Such parts are often made in the form of bushings and rings, and you can review the range in the product catalogue.
The advantage of polyurethane here is not only wear resistance: it provides a better seal at the joint between metal and polymer, which rules out the delamination typical of rubber.
The trade-off is worth noting too. A polyurethane silent block makes the suspension stiffer than soft rubber, so ride comfort drops slightly. On passenger vehicles this is noticeable, but for haulage and agricultural machinery, where reliability and handling under load come first, a stiffer suspension is rather an advantage. The vehicle behaves more stably on wet and slippery roads, and the assembly holds its set geometry longer. That is why the choice of hardness is always tied to the type of machinery and the operating conditions rather than to a universal standard.
Silent blocks made to size
Silent blocks and bushings at the TIMOL factory are made by free casting, which yields a solid part with no seams. This matters for suspension assemblies, because a seam is a potential weak point along which a part fails under cyclic load. Casting technology makes it possible to hold the inner and outer diameter precisely to a specific sleeve.
Production is possible to a drawing, a 3D model or a sample of a worn part. If there is no original drawing, it is enough to provide the old bushing, from which the seating dimensions are taken. This approach lets us restore rare or discontinued positions without being tied to the automakers’ factory catalogues. Details on made-to-order production are given in the factory services section.
The hardness of the material is selected by the technologist to suit the mass of the assembly and the working conditions, which reduces the risk of premature settling or excessive stiffness.
How to order polyurethane for silent blocks at the TIMOL factory
You can buy polyurethane for silent block manufacturing or order finished bushings for your assembly directly from the manufacturer in Dnipro. Working directly with the factory means the hardness and geometry of the part are matched to the specific task rather than a universal compromise being offered.
For a quote, prepare a drawing, dimensions or a sample of the part and describe the working conditions of the assembly: the type of machinery, the loads, the temperature range. The technologist will recommend a polyurethane grade and hardness and then produce the part. You can place an order and get a consultation through the contacts page. Making a silent block to size gives a precise fit and a longer service life than picking an approximate off-the-shelf equivalent.