<div class="htmlview paragraph">To improve both the durability and reliability of the main bearing, and also to reduce friction, a technique was developed to measure transient sliding friction of main bearings in a firing engine. The movement of bearing pin was also measured at same time to analyze the relationship between friction characteristics and oil film thickness.</div> <div class="htmlview paragraph">Test results are as follows: Main bearing friction is fairly constant over one working cycle, an increase is observed in a short time. When oil film thickness becomes minimums, engine load has some influence on the average main bearing friction value, but affects peak value substaintially. With an increase of engine speed, both average and peak values increase.</div>