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SAE J1269 is a standard test defined by the Society of Automotive Engineers [1] to measure the rolling resistance of tires under conditions of thermal equilibrium. [2] [3] SAE J2452 is an alternative procedure for measuring rolling resistance under conditions similar to a vehicle coastdown event, where the tire is in a roughly isothermal condition (but not thermal equilibrium).
In GvK diagram, the x-axis is the vehicle velocity, and the y-axis is the dimensionless specific resistance.The same kind of vehicle may have multiple different operating velocities, with different corresponding specific resistances, consequently each kind of vehicle generally correspond to a whole region on the GvK diagram, but only the lower-edge of the region is plotted, since specific ...
Various other characteristics affect the coefficient of drag as well, and are taken into account in these examples. Many sports cars have a surprisingly high drag coefficient, as downforce implies drag, while others are designed to be highly aerodynamic in pursuit of a speed and efficiency, and as a result have much lower drag coefficients.
Large truck tires 0.0055 [23] Typical BMX bicycle tires used for solar cars 0.0065 [30] EU passenger car tyre label fuel efficiency class A (upper limit) 0.0062 to 0.0150 [31] Car tire measurements 0.0100 to 0.0150 [32] Ordinary car tires on concrete 0.0385 to 0.0730 [33] Stage coach (19th century) on dirt road. Soft snow on road for worst case ...
Automotive aerodynamics is the study of the aerodynamics of road vehicles. Its main goals are reducing drag and wind noise, minimizing noise emission, and preventing undesired lift forces and other causes of aerodynamic instability at high speeds.
Braking distance refers to the distance a vehicle will travel from the point when its brakes are fully applied to when it comes to a complete stop. It is primarily affected by the original speed of the vehicle and the coefficient of friction between the tires and the road surface, [Note 1] and negligibly by the tires' rolling resistance and vehicle's air drag.
Rolling resistance is the main key factor in measuring the energy efficiency of a tyre and has direct influence on the fuel consumption of a vehicle. A set of tyres of the green class "A" compared to a "G" class can reduce fuel consumption by 9% [3] of a passenger car; even more for trucks.
Low rolling resistance tires are designed to reduce the energy loss as a tire rolls, decreasing the required rolling effort — and in the case of automotive applications, improving vehicle fuel efficiency as approximately 5–15% of the fuel consumed by a typical gas car may be used to overcome rolling resistance. [1]