Torque

Torque is the measure of rotational force that an engine produces. While horsepower describes how quickly work can be done, torque measures the twisting force available to do that work. In the United States, engine torque is measured in pound-feet (lb-ft), while most other countries use Newton-meters (Nm). Mathematically, horsepower and torque are related: HP = (Torque × RPM) / 5,252.

Understanding torque is essential for selecting the right vehicle for specific needs. Low-end torque (available at low RPM) matters most for towing, hauling, and off-road capability — it determines how effectively a vehicle can pull heavy loads from a stop or climb steep grades. This is why diesel engines, which produce high torque at low RPM, are preferred for heavy-duty trucks. Peak torque at higher RPM contributes to acceleration performance.

In the repair context, torque specifications are critical for proper fastener installation. Every bolt in a vehicle has a specific torque specification — the exact amount of tightening force that ensures the fastener is secure without being over-stressed. Mechanics use a torque wrench to tighten critical fasteners (head bolts, wheel lugs, suspension components, drain plugs) to the manufacturer's specified values. Under-torquing can lead to loose components and failures; over-torquing can strip threads, crack castings, or cause bolt fatigue.

Many critical fasteners also require a specific torque sequence (the order in which bolts are tightened) and may use a torque-to-yield method where the bolt is intentionally stretched to a precise point for optimal clamping force. These fasteners are typically single-use and must be replaced each time they are removed.