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The effects of crank-pin surface circumferential waviness, also known as journal lobing or chatter in engineering terms, on bearing performance have been investigated by carrying out an elastohydrodynamic lubrication analysis. The big-end bearing in a 2.0 liter diesel engine has been used for the study. The operating condition is that of maximum torque with engine running at 1800rpm. The crank pin has been assumed to have 2, 3, 5, 9, 15, 30 and 50 lobes. Sufficiently fine meshes have been used to model the lobe profiles. Solutions cover a large range of lobe amplitude and lobe orientation angles. The results show that journal lobing has adverse effects on the bearing's lubrication performance because it severely reduces the oil film thickness and significantly increase the oil film pressure. The combination of large lobe numbers and big lobe amplitudes is particularly detrimental.

The constant engine development requirements of increased durability with lower cost, size and power loss need innovations in technology from designers and manufacturers of critical components such an engine bearings. A detailed experimental program has shown that a connecting rod bearing with “end-relief” grooves can give surprising and unexpected benefits in reducing bearing temperature. Bearing shells with “end-relief” resulted in an effective bearing width reduced by 6mm or 30%, yet still gave benefits in temperature reduction. The depth of the “end-relief” was too large for any hydrodynamic oil film to generate pressure to support the applied load.