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Ride height orground clearance is the amount of space between the base of an automobiletire and the lowest point of the automobile, typically the bottom exterior of the differential housing (even though the lowershock 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 betweenhandling,ride quality, and practicality.
A higher ride height and ground clearance means that thewheels have more vertical room to travel and absorb road shocks. Also, the car is more capable of being driven on surfaces that are not level, without the scraping against surface obstacles and possibly damaging the chassis and underbody.
For a higher ride height, thecenter of mass of the car is higher, which makes for less precise and more dangerous handling characteristics (most notably, the chance ofrollover is higher). Higher ride heights will typically adversely affectaerodynamic properties. This is whysports cars typically have very low clearances, whileoff-road vehicles andSUVs have higher ones.
A road car usually has a ride height around 16–17 cm (6.3–6.7 in), while anSUV usually lies around 19–22 cm (7.5–8.7 in). Two well-known extremes are theFerrari F40 with a 12.5 cm (4.9 in) ride height[1] and theHummer 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 usedunderslung frames to achieve a lower ride height and the consequent improvement in center of gravity. The 1905–14 cars of theAmerican 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 theAudi Allroad Quattro andTesla Model S) haveheight adjustable suspension, which can vary the ride height by adjusting thehydropneumatic suspension orair suspension. This adjustment can be automatic, depending on road conditions, and/or the settings selected by the driver. Many buses include a kneeling feature to make it easier for passengers to board and alight, and a ferry lift feature to increase the ground clearance, which is useful for steep ground transitions, such as driving onto ferries, as the name suggests.
Other, simpler suspension systems, such ascoilover springs, offer a way of manually adjusting ride height (and often, spring stiffness) by compressing the springin situ, using a threaded shaft and adjustable knob or nut.
Lowering a car'ssuspension 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 realizedcar handling improvement from the lowercenter 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 suspensionsprings, and is the essence of many aftermarket suspension kits supplied by manufacturers such asKW,Eibach,[5] andH&R.[6] For trucks, lifted trucks are popular with truck owners, who often upsize their wheels and tires when lifting their vehicles.
Forarmored fighting vehicles (AFV), ground clearance presents an additional factor in a vehicle's overall performance: a lower ground clearance means that the vehicle minus thechassis 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-wheeltractor-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 raisedrailroad crossings. Their extremely longwheelbase 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 (such as South Australia) 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 highcenter of gravity, which could cause the vehicle to be unstable or evenflip.
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 lowestsprung mass and the ground.[citation needed]
