Torque is Force x Distance
Units is Newton Meters ( do not use useless non metric crap)
Torque applies to any force/distance situation starting from a screwedriver twist to a soace shuttle launch.
For automobiles, TORQUE in layman terms is the measurement of the twisting or rotational force.
An engine crankshat pushes the pistons turning rotational KE into Torque. So a car uses its HORSEPOWER ( 1 HP = 746 Watts)to make Torque.
An engine will run evenly from somewhere around idle speed (about 800 revolutions per minute or rpm) to its "red line" which might be anywhere from 4000rpm for an older engine to 12000rpm for a Formula One engine. The power and torque will vary through this rev range.
Torque increases as revs increase from idle to a certain figure and then falls as the revs increase above this figure. Acceleration is proportional to the amount of force pushing the vehicle forward, so maximum acceleration in a given gear is attained when maximum torque is attained.
Power is force (~torque) multiplied by speed (~revs) so power increases with revs up to and past the point of maximum torque. However, at still higher revs the engine starts to be limited by the amount of air that it can draw in (4 valves per cylinder help) and torque then decreases more rapidly than the revs increase and therefore power also decreases.
Power is force multiplied by speed, and maximum acceleration is attained by having maximum propulsive force at the wheels. Use of a low gear-ratio multiplies the engine torque at the wheel (at the price of having the engine rotate more quickly). Maximum acceleration at a given speed is attained by having the engine operating at maximum power.
For example a CAT bulldozer with a 12 L V8 diesel pumps out 240 HP. A maxima V6 3 liter has 240 HP.
However, this CAT dozer will have 1500 Nm torque where as Maxima will have 100Nm.
Also this Torque from the CAT will be at sub 1000 RPM where as Maxima needs to be gassed to 2500 RPM for max torque.
So maxima will speed away into oblivion comapred to CAT. But when it comes to that twisting force called torque, the bulldozer will blow the car away because its blade needs to push horrendous amounts of heavy dirt and rock ahead of the vehicle, while the car just needs to push itself and a driver through the air.
Tyres do help in torque .. but marginal performance. No matter what you try it will be 2-7% gain max.
If you divide Torque by the radius of wheels, that is the ROAD GRIP ratio.
Question : At what RPM does an electric motor have max Torque ?