Sunday, May 24, 2009

Your Vehicle's ride quality

Ride quality refers to the degree of protection offered vehicle occupants from uneven elements in the road surface, or the terrain if driving off-road. A car with very good ride quality is also a comfortable car to ride in. Cars which disturb vehicle occupants with major or minor road irregularities would be judged to have low ride quality. Key factors for ride quality are Whole body vibration and noise.
While pleasant, the comfort of the vehicle driver is also important for car safety, both because of driver fatigue on long journeys in uncomfortable vehicles, and also because road disruption can impact the driver's ability to control the vehicle. Early vehicles, like the Ford Model T, with its live axle suspension design, were both uncomfortable and handled poorly.

Automakers often perceive providing an adequate degree of ride quality as a compromise with car handling, because cars with firm suspension offer more roll stiffness, keeping the tires more perpendicular to the road. Similarly, a lower center of gravity is more ideal for handling, but leaves very little vertical space for bump absorption before these disturb the passengers.

Over time, technology has shifted this curve outward, so that it is possible to offer vehicles that are extremely comfortable and still handle very well, like the Citro├źn DS, or vehicles with excellent handling that are also reasonably comfortable, like the BMW 5-Series.

Technology from the latter half of the 20th Century is not the only means to achieve ride quality - massive weight coupled with very soft suspension settings is also an option - as seen on the Rolls-Royce Silver Cloud and the Cadillac in the 1950s and 1960s, which weighed over 5,000 lbs. The downside is that massive weight also contributes to poor fuel efficiency. In the United States, the Corporate Average Fuel Economy standard effectively prohibits the return to a passenger vehicle fleet of what now appear to be comically oversized cars from the 1950s and 1960s. In most of the rest of the world, the high price of gasoline effectively prevents most motorists from using massively heavy cars.

Load bearing also interferes with ride quality - the suspension settings are very stiff so the vehicle doesn't change pitch when loaded - most trucks thus do not ride particularly comfortably. In passenger vehicles, self-leveling suspension has been introduced to counteract this effect.

Road construction quality and maintenance have a direct impact on ride quality in vehicles. In jurisdictions where all roads are as smooth as pool tables, the passengers are undisturbed already and the vehicle can be optimized for a higher degree of handling. In most industrialized countries, as well as in many development countries, pavement condition is scanned on road network level using laser/inertial road Profilometers. The Profilometer records road geometry and condition while driving at highway speed. Results from Profilometry can be used to design an optimal geometric pavement repair, eliminating all long wave unevenness, roughness, erroneous cross slope magnitudes and undesired cross slope variance, with the least road grinding and paving efforts. The outcome is a surface with superior ride quality.

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