BMW Rod Bearing Failure

BMW is infamous for engine bearing failure on their line of M3 and M5 engines. In 2019 BMW acknowledged this failure by publishing rod bearing clearance specifications. Engine builder experts have said that BMW engines have been built with a bearing clearance under the recommendation from the performance industry. BMWs also have an issue called “tolerance stacking” which reduces the bearing clearance to below acceptable dimensions. Lack of proper clearance limits oil lubrication between the crank journal and the rod bearings. This causes premature wearing of the rod bearings. This rubbing also creates debris which can damage other engine parts. Because of this, we see BMW engines wearing through their bearings early. In some cases when the tolerance stack was a factor, there have been massive engine failures on cars with very low miles, some even as low as 60,000 miles. In this case, the vehicle is in need of a complete replacement engine. This is why many S54/S65/S85 BMW owners will change their rod bearings before they have an issue.