Ride height

Last updated
Chevrolet Suburban raised with aftermarket wheels and suspension mods - note much greater ground clearance under front with independent suspension, compared to under rear live axle differential. 6386th RTU Logistics (14238412413).jpg
Chevrolet Suburban raised with aftermarket wheels and suspension mods  note much greater ground clearance under front with independent suspension, compared to under rear live axle differential.

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 axle); 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.

Contents

Function

Ground clearance affects breakover angle of a car. (bdeg = Breakover angle; C = Underside of chassis; W = Wheel; G = Ground; M = Midpoint of wheelbase) Breakover angle diagram.svg
Ground clearance affects breakover angle of a car. (β° = Breakover angle; C = Underside of chassis; W = Wheel; G = Ground; M = Midpoint of wheelbase)

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.

Example ride heights

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 heightCar 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

Specialized uses

Underslung frame

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

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.

Height adjustable

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.

Adjustable shock absorber

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.

BMW E46 "stanced" using aftermarket suspension kit Lowered BMW M3.jpg
BMW E46 "stanced" using aftermarket suspension kit

Aftermarket

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 Eibach [5] and H&R. [6]

Military

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.

Trucks

MUTCD warning sign for a low-ground-clearance crossing MUTCD W10-5.svg
MUTCD warning sign for a low-ground-clearance crossing

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.

Buses

In some areas buses are required to have a ground clearance of at least 100 mm (3+1516 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.

See also

Related Research Articles

<span class="mw-page-title-main">Camber angle</span> Angle between a wheels vertical axis and the vehicles vertical axis

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 design of steering and suspension. If the top of the wheel is farther out than the bottom, it is called positive camber; if the bottom of the wheel is farther out than the top, it is called negative camber.

<span class="mw-page-title-main">Car suspension</span> Suspension system for a vehicle

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.

<span class="mw-page-title-main">Hydropneumatic suspension</span> Pneumatics

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, notably Rolls-Royce, Bmw 5-Series e34 Touring, Maserati and Peugeot. It was also used on Berliet trucks and has been used on Mercedes-Benz cars, where it is known as Active Body Control. The Toyota Soarer UZZ32 "Limited" was fitted with a fully integrated four-wheel steering and a complex, computer-controlled hydraulic Toyota Active Control Suspension in 1991. Similar systems are also widely used on modern tanks and other large military vehicles. The suspension was referred to as fr: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.

<span class="mw-page-title-main">Car tuning</span> Modification of a cars performance

Car tuning is the modification of a car to optimise it for a different set of performance requirements from those it was originally designed to meet. Most commonly this is higher engine performance and dynamic handling characteristics but cars may also be altered to provide better fuel economy, or smoother response. The goal when tuning is the improvement of a vehicle's overall performance in response to the user's needs. Often, tuning is done at the expense of emissions performance, component reliability and occupant comfort.

<span class="mw-page-title-main">Weight transfer</span> Change in wheel load or center of mass in a vehicle

Weight transfer and load transfer are two expressions used somewhat confusingly to describe two distinct effects:

<span class="mw-page-title-main">Vehicle rollover</span> Car accident in which the vehicle tips or rolls over

A rollover or overturn is a type of vehicle crash in which a vehicle tips over onto its side or roof. Rollovers have a higher fatality rate than other types of vehicle collisions.

<span class="mw-page-title-main">Coilover</span> Automobile suspension device

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. 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, later followed by the Mercedes 130H/150H/170H, the Standard Superior, the Volkswagen Beetle and its derivatives, the Chevrolet Corvair, and the roll-over prone M151 jeep amongst others.

<span class="mw-page-title-main">Anti-roll bar</span> Device that reduces the body roll of a vehicle

An anti-roll bar is a part of many automobile suspensions that helps reduce the body roll of a vehicle during fast cornering or over road irregularities. It connects opposite (left/right) wheels together through short lever arms linked by a torsion spring. An anti-roll bar increases the suspension's roll stiffness—its resistance to roll in turns—independent of its spring rate in the vertical direction. The first stabilizer bar patent was awarded to Canadian inventor Stephen Coleman of Fredericton, New Brunswick on April 22, 1919.

<span class="mw-page-title-main">Active Body Control</span>

Active Body Control, or ABC, is the Mercedes-Benz brand name used to describe electronically controlled hydropneumatic suspension.

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.

<span class="mw-page-title-main">Suspension lift</span>

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. 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.

Self-levelling refers to an automobile suspension system that maintains a constant ride height of the vehicle above the road, regardless of load.

<span class="mw-page-title-main">Height adjustable suspension</span> Automobile suspension systems

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.

Ride quality refers to a vehicle's effectiveness in insulating the occupants from undulations in the road surface such as bumps or corrugations. A vehicle with good ride quality provides comfort for the driver and the passengers.

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 semi-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.

<span class="mw-page-title-main">Tank transporter</span>

A tank transporter is a combination of a heavy tractor unit or a ballast tractor and a mating full trailer, hydraulic modular trailer or semi-trailer, used for transporting tanks and other armoured fighting vehicles. Some also function as tank recovery vehicles, the tractors of which may be armoured for protection in combat conditions.

Pull-rod suspension and push-rod suspension refer to a specialised type of automotive suspension system which is largely based on a double-wishbone system, incorporating elements of the commonly used MacPherson strut.

References

  1. 1987 Ferrari F40 specifications | technical data | performance | fuel economy | emissions | dimensions | horsepower | torque | weight
  2. How much Ground Clearance is Good Ground Clearance in India?
  3. "Under-Budget Underslung - 1929 Dodge Roadster - Hot Rod Magazine". www.hotrod.com. Archived from the original on 2007-01-02.
  4. "BMW Technology Guide : Self-levelling suspension". BMW. Retrieved 2018-05-16.
  5. Eibach
  6. H&R
  7. "Code of Practice for Buses", section 3.2: Ground Clearance