Friday, August 25, 2017

Why does Rolling Resistance matter in the real world?

Some 13% of the power produced by the engine to move a long haul rig along a smooth road at 65 mph is “lost” due to Rolling Resistance. What is it, what causes it, and how can you help to reduce it.

What is Rolling Resistance?
Rolling Resistance is the term used for the energy required to roll a tire over a particular road surface.

It can be viewed as a Parasitic Power Loss, accounting some 13% of the total energy required to move a long haul tractor-trailer combination over a smooth road at 65 mph.

What causes Rolling Resistance?
Rolling Resistance is caused by the following factors

The deformation of the tire in the contact patch and the sidewalls as it rolls (this accounts for some 80% – 95% of Rolling Resistance – Michelin)
Aerodynamic drag of the rotating tire
Friction (microslippage) between the tread and the road surface
Rolling Resistance is also greatly impacted by condition of the road surface.

Why does it matter?
Because it is energy LOST, it is equivalent to a power loss. Power made by the engine is not fully usable, and inhibits forward movement of the vehicle.

Fuel consumption is therefore increased because of this parasitic loss.

How can you reduce Rolling Resistance?

  • Keep tires properly inflated. Properly inflated tires minimize deformation of the contact patch and side walls, and keeps energy loss to a minimum.
  • Use “green tires”, with rubber compounds and treads designed to minimize this energy loss. As much as 35 HP may be “saved” at 65 mph at 80,000 lb.
  • Use of single wide-base tires in place of dual assembly tires. Two dual tires have four sidewalls as opposed to two for a single tire, thus reducing the side wall flex and energy loss.
  • Larger diameter tires have slightly lower energy loss due to the fact that there is less bending of the tire as it enters and leaves the contact patch.

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