# What is the rolling resistance of the tyre?

Ever wonder, what is “tyre rolling resistance”? And how it may affect your tyre-purchasing choice and fuel efficiency? Today, we will elaborate on tyre rolling resistance and the means by which low resistance tyres can expand the eco-friendliness of your vehicle.

In order for your vehicle to move, energy needs to be transferred to the engine and other systems in the vehicle. This energy is generated via gas or electricity. That outcomes is your tyres turning and enough force being developed to move your car.

However, your vehicle must conquer a variety of resisting forces that can make it impervious for your vehicle to move forward. One of those resistive forces is the rolling resistance of the tyre.

The key principle of rolling resistance is known as hysteresis. Hysteresis is basically the loss of energy as tyre rolls and overcome resistance. The loss of energy due to resistance must be overwhelmed by the vehicle’s engine.

Excessive rolling resistance is one of the common factors that hurt the life of a car tyre as well as the fuel economy. That is why today tire manufacturers such as Michelin Tires, Goodyear, or Pirelli claim that their tires offer the least rolling resistance to attract more customers.

### Calculating the rolling resistance of a tyre

Rolling resistance coefficient (RRC or Crr) is used in expressing the rolling resistance of the tyre. The energy consumption of the vehicle will be less if the rolling resistance coefficient is lower.

Following is the formula for calculating the rolling resistance of tyre:

( N/Lbs) = P^α x Z^β x (a + bxV + cxVxV)

• P is the tyre inflation pressure ( kPa / psi)
• Z is the applied load for vehicle weight ( N /Lbs)
• V is the vehicle speed ( km/h / mph)
• alpha, beta, a, b, c are the coefficients for the model.

### Key components affecting tyre rolling resistance

The most significant component affecting the tyre rolling resistance includes:

#### Weight

The lower weight of the vehicle with tyres, the lower resistance. As a rule, low-profile, limited tyres are lighter, as well as the tyres with lower height have lower rolling resistance.

#### Aerodynamics

The resistance due to aerodynamics is the opposition of the encompassing air and the drag force. Resistance due to aerodynamics is directly proportional to the speed of the vehicle.

#### Tyre pressure

Tyres with low air pressure can cause expanded contact of the tyre with the ground while increasing the resistance up to 30%.

The elastic compound and enhanced tread design can immensely influence the rolling resistance up to 60%.

#### Tyres with low rolling resistance

Following are the tyres rated with the lowest resistance coefficient

 Tyres Rolling resistance coefficient Bridgestone B381 P185/70R14 0.00615 Michelin SYMMETRY P225/60R16 0.00650 Michelin TIGER PAW AWP P225/60R16 0.00683 Bridgestone DUELER H/T 113S P265/70R17 0.00700 BFGoodrich RUGGED TRAIL T/A P285/70R17 0.00709 Michelin LTX A/S P255/65R17 0.00754 Goodyear INTEGRITY (OE) P225/60R16 0.00758 Bridgestone INSIGNIA SE 200 89S P195/65R15 0.00760 BFGoodrich RUGGED TRAIL T/A P245/65R17 0.00767 Continental Ameri-G4S WS P235/75R15 0.00780 Continental CrossContact LX 0.00783 Michelin TPAW TOURING TR/SR P215/70R16 0.00795 Bridgestone DUELER H/T 104S P235/70R16 0.00810 Goodyear Invicta GL 235/75R15 0.00813 Continental ContiTouring Contact CH95 P205/55R16 0.00825 Michelin CROSS TERRAIN SUV P255/75R17 0.00829 Michelin PILOT PRIMACY 275/50R19 0.00833 Michelin ENERGY LX4 P225/60R16 0.00850 Michelin PILOT LTX P265/70R17 0.00854 Michelin ENERGY MXV4 PLUS 235/65R17 0.00855

Apart from fuel efficient and eco-friendly tyres such as Michelin pilot sport 3 are manufactured for the sole purpose of providing high performance.

### Rolling resistance coefficient values for energy efficiency

 Cl tyres C2 tyres C3 tyres RRC in kg/t Energy efficiency class RRC in kg/t Energy efficiency class RRC in kg/t Energy efficiency class RRC 6,5 A RRC 5,5 A RRC 4,0 A 6,6 12ItC 7,7 B 5,6 fklIC 6,7 B 4,1 12ItC 5,0 B 7,8 .1kFtC 9,0 C 6,8 IztRC 8,0 C 5,1 1,tFtC 6,0 C Empty D Empty D 6,1 17tRC 7,0 D 9,1 1,tFtC 10,5 E 8,1 1:tRC 9,2 E 7,1 1,(F&C 8,0 E 10,6121kC 12,0 F 9,3 FtIkC 10,5 F RRC 8,1 F RRC 12,1 G RRC 10,6 G Empty G

### Final words

Tyre rolling resistance is the 70% of resistive forces acting upon a vehicle, that is the reason it is very important to keep the rolling resistance coefficient of the tyre low.

Resistance is one of the vehicle energy shoppers. Decreasing the rolling resistance of tyres prompts a decrease in fuel utilization and carbon dioxide emissions.

A tyre maker can lessen tread depth in order to counter rolling resistance. Nevertheless, there will be a comparing decrease in tyre wear life. To beat this, innovations are being worked on in order to beat rolling resistance while keeping the tyre wear life prolonged.