Bearing clearance is the distance between the crankshaft journal and the bearing surface. It is usually referred to as oil clearance, as that's what is occupying the space.
the clearance is measured at the top of the bearing with the help of a feeler gauge
There is no simple formula to calculate the metal bearing clearance. Manufacturers must specify the clearance for each individual bearing.
.0010" to .0020" oil clearance
For a complete guide on checking tilting pad clearance in journal bearing visit johncraneorion.com/literature/catalogs/catalog.pdf
A bearing backlash is what happens when the bearing loses motion or clearance. This tends to be caused by gaps that cause a period of non-motion.
the bearing which have adequate clearance in bearing housing to allow thermal expansion in the shaft, are called floating bearings M.Rafique Burero
You wouldn't want oil to be taking up part of your clearance and give a false reading with the plastigage.
.002" is what I have on a fresh rebuild.
If there were no operating clearance the clutch release bearing would constantly be in contact with the spring diaphragm causing wear on both the diaphragm and the bearing itself, also the bearing pushing on the diaphragm could cause the clutch friction plate to not be fully engaged and slip.
The main bearing and rod bearinging clearance is usually in the manual. However, if worse comes to worse, you can find it on your rods in the truck.
Plastigauge
In order to prevent continuous rotation of the release bearing - this prevents premature wear of the bearing To ensure that the full spring pressure and clamping force is applied at the clutch contact faces The clearance is normally measured at the clutch pedal