King pMax Black™ Bearing Overlay is the Strongest in the Industry - Engine Builder Magazine
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King pMax Black™ Bearing Overlay is the Strongest in the Industry


King’s newly developed engine bearing measures 18.1 Vickers hardness compared to a 14 hardness or less found in competitors’ performance bearings.

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By Dr. Dmitri Kopeliovich, R & D manager, King Engine Bearings

The design of internal combustion engines has been continuously modified. Engine output and efficiency have dramatically increased due to the great efforts of engineers and the latest technological achievements in materials engineering, electronics and computer control.

The conditions under which the engine bearings operate have also changed over the years. Greater output, higher combustion pressures and engine downsizing result in higher specific loads being applied to the bearings. The trend toward lower oil viscosity and reduced ZDDP content in motor oils has forced bearings in modern engines to operate in a regime of lower minimal oil film thickness, resulting in an increased probability of fatigue, abnormally fast wear and seizure.


Over the next few months, we will address engine bearing issues, component material and load capacity to give engine builders a better understanding of the importance of choosing the correct bearing for their build.

Understanding Overlay
In our first installment, we will address overlay thickness as it pertains to performance applications. Overlay thickness has always been the result of a compromise between the required load capacity and the bearing’s anti-friction properties. However, in racecars, the required compromise is unachievable. The traditional tri-metal engine bearing, which has been used for decades, becomes unsuitable for these applications.


Enter pMax Black™ Bearings Designed for Race Conditions
The solution for this problem lies in developing bearing materials that perform as stronger overlays with greater fatigue strength and better wear resistance.

King Engine Bearings has developed an effective method of producing such a material by means of a surface hardening process that strengthens lead based overlays. This innovative technique enables the formation of an ultra-thin hardened shield on the overlay surface.

This shield, of nano-scale thickness, is sufficient to effectively suppress the formation of fatigue cracks on the surface.

It measures 18.1 Vickers hardness (HV) compared to 14 HV less found in competitors’ performance bearings. This results in a minimum 29% stronger overlay surface that withstands greater loads and delays or prevents the formation of fatigue cracks and distress.


At the same time, the properties of excellent seizure resistance, conformability and embedability — which are characteristics of soft overlays — are preserved.

This new overlay, called pMax Black, has proven its effectiveness in increasing the fatigue strength of high performance tri-metal bearings. All King XP series high performance bearings are manufactured with this hardened pMax Black overlay. These bearings are easily recognizable by their distinctive dark color.
See Figure 1.


Figure 1: King XP bearings with pMax Black™ overlay

Figure 2:  Rig Tested bearings

Figure 2: Rig Tested bearings

The new material has been tested in comparison with traditional tri-metal bearings. The results of the comparative tests conducted in King’s Test Rig are presented in Figure 2.

The tests were performed under a bearing load of 10,200 psi for 4,300,000 cycles. Both conventional and pMax Black bearings had the same dimensions.

The test results are as follows:
• The conventional high performance bearing has a large area (about 30% of the surface area) with overlay fatigue cracks.
• King pMax Black has no fatigue cracks.


Note: In our next installment, we will take a look at the effect of bearing geometry on load capacity and performance.

Source: King Engine Bearing Specialists


Engine Builder Magazine