B-pillar: the roof support between a car's front door window and rear side window, if there is one.
balance shalt: a shaft designed so that, as it rotates, it vibrates in a way that reduces or cancels some of the vibration produced by an engine. Not essential to an engine's operation, balance shafts are nonetheless becoming increasingly common as a means of engine refinement. Balance-shafted four-cylinder engines use two shafts turning in opposite directions on either side of the engine's crankshaft. A single balance shaft is used when fitted to three-cylinder and V-6 engines.
ball joint: a flexible joint consisting of a ball in a socket, used primarily in front suspensions because it can accommodate a wide range of angular motion.
beam axle: a rigid axle supporting the non-driven wheels. Also called a dead axle.
beltline: the line running around a car's body formed by the bottom edges of its glass panels
bevel gears: a gearset employing gears shaped like slices of a cone, which allows the axes of the gears to be nonparallel. Bevel gears are used to transmit motion through an angle.
boost pressure: the increase above atmospheric pressure produced inside the intake manifold by any supercharger. It is commonly measured in psi, inches of mercury, or bar.
brake bias: the front/rear distribution of a car's braking power. For the shortest stopping distance, brake bias should match the car's traction at each end during hard braking brake modulation: the process of varying pedal pressure to hold a car's brakes on the verge of lockup. Ideally, the brakes will unlock with only a slight reduction in the pressure needed to lock them. Typically, however, a considerable pressure reduction is required.
brake torquing: a procedure generally used in performance tests to improve the off-the-line acceleration of a car equipped with an automatic transmission. It is executed by firmly depressing the brake with the left foot, applying the throttle with the car in gear to increase engine rpm, then releasing the brakes. Brake torquing is particularly effective with turbo charged cars because it helps overcome turbo lag.
breathing (engine): a term used to describe an engine's ability to fill its cylinders with air-fuel mixture and then discharge the burnt exhaust gases. In general, the more air-fuel mixture an engine burns the more power it produces.
bushing: a simple suspension bearing that accommodates limited rotary motion, typically made of two coaxial steel tubes bonded to a sleeve of rubber between them. The compliance of the bushing in different directions has a great effect on ride harshness and handling.