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Ride height or ground clearance is the amount of space between the base of an automobile tire and the lowest point of the automobile, typically the bottom exterior of the differential housing (even though the lower shock mounting point may be lower); or, more properly, to the shortest distance between a flat, level surface, and the lowest part of a vehicle other than those parts designed to contact the ground (such as tires, tracks, skis, etc.). Ground clearance is measured with standard vehicle equipment, and for cars, is usually given with no cargo or passengers.
Ground clearance is a critical factor in several important characteristics of a vehicle. For all vehicles, especially cars, variations in clearance represent a trade-off between handling, ride quality, and practicality.
A higher ride height and ground clearance means that the wheels have more vertical room to travel and absorb road shocks. Also, the car is more capable of being driven on roads that are not level, without the scraping against surface obstacles and possibly damaging the chassis and underbody.
For a higher ride height, the center of mass of the car is higher, which makes for less precise and more dangerous handling characteristics (most notably, the chance of rollover is higher). Higher ride heights will typically adversely affect aerodynamic properties. This is why sports cars typically have very low clearances, while off-road vehicles and SUVs have higher ones.
A road car usually has a ride height around 16–17 cm (6.3–6.7 in), while an SUV usually lies around 19–22 cm (7.5–8.7 in). Two well-known extremes are the Ferrari F40 with a 12.5 cm (4.9 in) ride height [1] and the Hummer H1 with a 40.64 cm (16.0 in) ride height.[ citation needed ]
The table below provides average ride height for different car types which were available on the market in India in 2020: [2]
Avg. ride height | Car type |
---|---|
135–140 mm (5.3–5.5 in) | Sports car |
165 mm (6.5 in) | Sedan |
168 mm (6.6 in) | Hatchback |
170 mm (6.7 in) | Compact car |
190–200 mm (7.5–7.9 in) | Compact SUV |
225 mm (8.9 in) | SUV |
Some cars have used underslung frames to achieve a lower ride height and the consequent improvement in center of gravity. The 1905-14 cars of the American Motor Car Company are one example. [3]
Self-leveling suspension systems are designed to maintain a constant ride height regardless of load. The suspension detects the load via mechanical or electronic means and raises or lowers the vehicle, by inflating cylinders in the suspension to lift the chassis higher. [4] Vehicles not equipped with self-leveling will pitch down at one end when laden; this adversely affects ride, handling, and aerodynamic properties.
Some modern automobiles (such as the Audi Allroad Quattro and Tesla Model S) have height adjustable suspension, which can vary the ride height by adjusting the hydropneumatic suspension or air suspension. This adjustment can be automatic, depending on road conditions, and/or the settings selected by the driver.
Other, simpler suspension systems, such as coilover springs, offer a way of manually adjusting ride height (and often, spring stiffness) by compressing the spring in situ, using a threaded shaft and adjustable knob or nut.
Lowering a car's suspension is a common and relatively inexpensive aftermarket modification. Many car enthusiasts prefer the more aggressive look of a lowered body,[ according to whom? ] and there is an easily realized car handling improvement from the lower center of gravity. Most passenger cars are produced such that one or two inches of lowering will not significantly increase the probability of damage. On most automobiles, ride height is modified by changing the length of the suspension springs, and is the essence of many aftermarket suspension kits supplied by manufacturers such as KW, Eibach [5] , and H&R. [6] For trucks, lifted trucks are popular with truck owners, who often upsize their wheels and tires when lifting their vehicles.
For armored fighting vehicles (AFV), ground clearance presents an additional factor in a vehicle's overall performance: a lower ground clearance means that the vehicle minus the chassis is lower to the ground and thus harder to spot and harder to hit. The final design of any AFV reflects a compromise between being a smaller target on one hand, and having greater battlefield mobility on the other. Very few AFVs have top speeds at which car-like handling becomes an issue, though rollovers can and do occur. By contrast, an AFV is far more likely to need high ground clearance than a road vehicle.
18-wheel tractor-trailers also have to take the ground clearance of both their tractor and especially trailer into consideration on certain areas of uneven terrain, such as raised railroad crossings. Their extremely long wheelbase means that such terrain could potentially catch the undercarriage of the trailer in the wide space between the axles, potentially leaving the truck stuck with no means to extricate itself.
In some areas buses are required to have a ground clearance of at least 100 mm (3+15⁄16 in). [7] Too much ride height can cause the vehicle to have an excessively high center of gravity, which could cause the vehicle to be unstable or even flip.
Colloquially referred to as differential clearance or diff clearance. Distance from bottom exterior of axle housing or bottom exterior of differential housing, whichever is lower, to the ground.[ citation needed ]
Distance between bottom of suspension components to ground. In vehicles with independent suspension this is typically the distance between the bottom of the lower control arm and the ground.[ citation needed ]
Distance between the bottom of the lowest sprung mass and the ground.[ citation needed ]
Vehicle dynamics is the study of vehicle motion, e.g., how a vehicle's forward movement changes in response to driver inputs, propulsion system outputs, ambient conditions, air/surface/water conditions, etc. Vehicle dynamics is a part of engineering primarily based on classical mechanics. It may be applied for motorized vehicles, bicycles and motorcycles, aircraft, and watercraft.
A chassis is the load-bearing framework of a manufactured object, which structurally supports the object in its construction and function. An example of a chassis is a vehicle frame, the underpart of a motor vehicle, on which the body is mounted; if the running gear such as wheels and transmission, and sometimes even the driver's seat, are included, then the assembly is described as a rolling chassis.
Camber angle is one of the angles made by the wheels of a vehicle; specifically, it is the angle between the vertical axis of a wheel and the vertical axis of the vehicle when viewed from the front or rear. It is used in the creation of steering and suspension. If the top of the wheel is further out than the bottom, it is called positive camber; if the bottom of the wheel is further out than the top, it is called negative camber.
A torsion bar suspension, also known as a torsion spring suspension, is any vehicle suspension that uses a torsion bar as its main weight-bearing spring. One end of a long metal bar is attached firmly to the vehicle chassis; the opposite end terminates in a lever, the torsion key, mounted perpendicular to the bar, that is attached to a suspension arm, a spindle, or the axle. Vertical motion of the wheel causes the bar to twist around its axis and is resisted by the bar's torsion resistance. The effective spring rate of the bar is determined by its length, cross section, shape, material, and manufacturing process.
Suspension is the system of tires, tire air, springs, shock absorbers and linkages that connects a vehicle to its wheels and allows relative motion between the two. Suspension systems must support both road holding/handling and ride quality, which are at odds with each other. The tuning of suspensions involves finding the right compromise. It is important for the suspension to keep the road wheel in contact with the road surface as much as possible, because all the road or ground forces acting on the vehicle do so through the contact patches of the tires. The suspension also protects the vehicle itself and any cargo or luggage from damage and wear. The design of front and rear suspension of a car may be different.
Hydropneumatic suspension is a type of motor vehicle suspension system, designed by Paul Magès, invented by Citroën, and fitted to Citroën cars, as well as being used under licence by other car manufacturers. Similar systems are also widely used on modern tanks and other large military vehicles. The suspension was referred to as Suspension oléopneumatique in early literature, pointing to oil and air as its main components.
Automobile handling and vehicle handling are descriptions of the way a wheeled vehicle responds and reacts to the inputs of a driver, as well as how it moves along a track or road. It is commonly judged by how a vehicle performs particularly during cornering, acceleration, and braking as well as on the vehicle's directional stability when moving in steady state condition.
A coilover is an automobile suspension device. The name coilover is an abbreviation of "coil over shock absorber".
A swing axle is a simple type of independent suspension designed and patented by Edmund Rumpler in 1903 for the rear axle of rear wheel drive vehicles. This was a revolutionary invention in automotive suspension, allowing driven (powered) wheels to follow uneven road surfaces independently, thus enabling the vehicle's wheels to maintain better road contact and holding; plus each wheel's reduced unsprung weight means their movements have less impact on the vehicle as a whole. The first automotive application was the Rumpler Tropfenwagen, another early example was the 1923 Tatra 11 later followed by the Mercedes 130H/150H/170H, the Standard Superior, the pre-facelift Volkswagen Beetle and most of its derivatives, the Chevrolet Corvair, and the roll-over prone M151 jeep amongst others.
A portal axle is an off-road vehicle suspension and drive technology where the axle tube or the half-shaft is offset from – usually above – the center of the wheel hub and where driving power is transferred to each wheel via a simple gearbox, built onto each hub. It gives two advantages: ground clearance is increased, particularly beneath the low-slung differential housing of the main axles — and secondly, any hub reduction gearing allows the axle half shafts to drive the same power but at reduced torque. This reduces load on the axle crown wheel and differential.
Air suspension is a type of vehicle suspension powered by an electric or engine-driven air pump or compressor. This compressor pumps the air into a flexible bellows, usually made from textile-reinforced rubber. Unlike hydropneumatic suspension, which offers many similar features, air suspension does not use pressurized liquid, but pressurized air. The air pressure inflates the bellows, and raises the chassis from the axle.
A suspension lift is a modification to a vehicle to raise the ride height. It is done for the purpose of improving the off road performance of SUVs or trucks and other off-road vehicles, or for cosmetic purposes. Suspension lifts can enable steeper approach, departure, and breakover angles, higher ground clearance, and helps accommodate larger wheels and tires. Due to the raised center of gravity, maximum safe operating angles can be reduced and roadholding is often significantly impaired. Sensors, transmitters and cameras may need to be recalibrated, physically relocated or modified to maintain normal functioning of features like AEB, ACC or FSD. Suspension lifts are also found on a number of high performance sports cars, in which a very low ground clearance is used to improve handling, using an aerodynamic effect known as downforce; examples include the Ferrari 488, Lamborghini Huracan, McLaren 720S, and the second generation Ford GT. Such vehicles activate the suspension lift while traversing road bumps and ramps to avoid damaging the front underbody of the vehicle when driving on public roads; the suspension lift is deactivated on race tracks and level roads.
A wheelchair-accessible van is a vehicle that has been modified by increasing the interior size of the vehicle and equipping it with a means of wheelchair entry, such as a wheelchair ramp or powered lift.
Self-levelling refers to an automobile suspension system that maintains a constant ride height of the vehicle above the road, regardless of load.
Height adjustable suspension is a feature of certain automobile suspension systems that allow the motorist to vary the ride height or ground clearance. This can be done for various reasons including giving better ground clearance over rough terrain, a lower ground clearance to improve performance and fuel economy at high speed, or for stylistic reasons. Such a feature requires fairly sophisticated engineering.
An active suspension is a type of automotive suspension that uses an onboard control system to control the vertical movement of the vehicle's wheels and axles relative to the chassis or vehicle frame, rather than the conventional passive suspension that relies solely on large springs to maintain static support and dampen the vertical wheel movements caused by the road surface. Active suspensions are divided into two classes: true active suspensions, and adaptive or semi-active suspensions. While adaptive suspensions only vary shock absorber firmness to match changing road or dynamic conditions, active suspensions use some type of actuator to raise and lower the chassis independently at each wheel.
In motorsport, the racing setup, car setup or vehicle setup is the set of adjustments made to the vehicle in order to optimize its behaviour for specific conditions. Vehicle setups are variable for a variety of reasons, ranging from weather, driver/rider preference and race track characteristics. Contrary to common misperceptions, setup is not used to maximize the performance of the engine, but to optimize it for the track at which it is being used. For example, motorcycle racers frequently detune their engines to reduce performance and power output so as to ensure the bike accelerates in a predictable manner.
In an automobile's suspension system, the scrub radius is the distance in front view between the king pin axis and the center of the contact patch of the wheel, where both would theoretically touch the road. It can be positive, negative or zero.
Bump steer is the term for the tendency of the wheel of a car to steer itself as it moves through the suspension stroke.
Breakover angle or rampover angle is the maximum possible supplementary angle that a vehicle, with at least one forward wheel and one rear wheel, can drive over without the apex of that angle touching any point of the vehicle other than the wheels. This definition is contingent upon the wheels being in continuous contact with the supporting surface(s). Breakover angle differs from ground clearance, which is the shortest distance between the ground and lowest point on the vehicle.