Rear Main Bearings

[Ken Morton]

I recall seeing an article about 750 racing ~ 60 years ago where the "fast boys" did not fit rev counters as they knew when to change up when they could hear the middle two pistons hitting the cylinder head. We do know that original Austin cranks do flex when abused, so with that in mind the main reason for rear bearing "rumble" was probably a little crank flex and the parallel  rollers in a new bearing would be overloaded at the ends if the engine was over revved in neutral. This could also be one of the reasons that most original Austin cranks fail at the rear web. I believe there has been some experimentation with using ball bearings at the rear.