Bore

The inner diameter of the engine cylinder is known as bore. It can be measured precisely by a vernier caliper or bore gauge. As the engine cylinder wears out with the passage of time, so the bore diameter changes to a larger value, hence the piston becomes lose in the cylinder, and power loss occurs. To correct this problem reboring to the next standard size is done and a new piston is placed. Bore is denoted by the letter ‘D’. It is usually measured in mm (S.I. units) or inches (metric units). It is used to calculate the engine capacity (cylinder volume).