LanciaStratos

Rod and Main Bearing Undersize Definitions / Explanations - READ ME

          Rod and Main Bearing Undersize Definitions / Explanations - READ ME

European engine bearings are sold with crankshaft grinding requirements of .25mm increments, which is the equivalent of .0098 inch imperial.   (.010 inches).    

The bearings are available in the following increments:

.25mm under = “.010 under”

.5mm under = “.020 under”

.75mm under = .030 under”

The thickness of the bearing shells vary by .10mm (.004") inches for each increment.    Counting both bearings = .008”.  This leaves a .002" gap if the crankshaft journal has been reduced by .010" inch from its original factory specified stock diameter.

Never assume that you have installed the correct bearings and double check that your machine shop has reground the crankshaft correctly.   Always check your bearing clearances with Plastigauge to determine clearances before final assembly.