Editing Steering (section)

===Four-wheel steering===
[[File:4WSselect.svg|thumb|right|200px|Speed-dependent four-wheel steering.]]
{{anchor|Four-wheel steering|4WS}}
Four-wheel steering is a system employed by some vehicles to improve steering response, increase vehicle stability while maneuvering at high speed, or to decrease [[turning radius]] at low speed.

====Active four-wheel steering====
In an active four-wheel steering system, all four wheels turn at the same time when the driver steers. In most active four-wheel steering systems, the rear wheels are steered by a computer and actuators.<ref name=":0">{{cite web|url=http://www.zf.com/corporate/en_de/products/product_range/cars/cars_akc__active_kinematics_control.shtml|title=Cars {{!}} AKC® - Active Kinematics Control - ZF Friedrichshafen AG|website=www.zf.com|language=en|access-date=2017-04-06|url-status=live|archive-url=https://web.archive.org/web/20170407054123/http://www.zf.com/corporate/en_de/products/product_range/cars/cars_akc__active_kinematics_control.shtml|archive-date=2017-04-07}}</ref> The rear wheels generally cannot turn as far as the front wheels. There can be controls to switch off the rear steering and options to steer only the rear wheels independently of the front wheels. At low speed (e.g. parking) the rear wheels turn opposite to the front wheels, reducing the turning radius, sometimes critical for large trucks, tractors, vehicles with trailers and passenger cars with a large wheelbase, while at higher speeds both front and rear wheels turn alike (electronically controlled), so that the vehicle may change position with less [[yaw angle|yaw]] and improved build-up of the lateral acceleration, enhancing straight-line stability.<ref name=":0" /><ref name=":1">{{cite web|url=http://www.bmw.com/com/en/newvehicles/5series/sedan/2016/showroom/driving_dynamic_efficiency.html|title=BMW 5 Series Sedan: Driving dynamics & Efficiency|last=AG|first=BMW|website=www.bmw.com|access-date=2017-04-06|url-status=live|archive-url=https://web.archive.org/web/20170406201629/http://www.bmw.com/com/en/newvehicles/5series/sedan/2016/showroom/driving_dynamic_efficiency.html|archive-date=2017-04-06}}</ref> The "snaking effect" experienced during motorway drives while towing a travel trailer is thus largely nullified.{{dubious|date=February 2012}}

Four-wheel steering found its most widespread use in [[monster truck]]s, where maneuverability in small arenas is critical, and it is also popular in large farm vehicles and trucks. Some of the modern European Intercity buses also utilize four-wheel steering to assist maneuverability in bus terminals, and also to improve road stability. Mazda were pioneers in applying four-wheel steering to automobiles, showing it on their 1984 Mazda MX-02 concept car, where the rear wheels counter-steered at low speeds.<ref name=TM585>{{cite magazine | magazine = Tekniikan Maailma | ref = TM | date = 1985-03-19 | number = 5/85 | volume = 41 | issn = 0355-4287 | title = Nelosten vuosi | trans-title = Year of the Four | last = Lindell | first = Hannu | publisher = TM-Julkaisu | location = Helsinki | language = fi | page = Automaailma 3 }}</ref> Mazda proceeded to offer a version of this electronic four-wheel steering system on the [[Mazda 626]] and [[Mazda MX-6|MX6]] in 1988. The first rally vehicle to use the technology was the [[Peugeot 405 Turbo 16]], which debuted at the 1988 Pikes Peak International Hill Climb.<ref>{{cite web|title=1988 Peugeot 405 T16 GR Pikes Peak|url=http://www.supercars.net/cars/5381.html|access-date=2015-03-16}}</ref>

Previously, [[Honda]] had mechanical four-wheel steering as an option in their 1987–2001 [[Honda Prelude|Prelude]] and [[Honda Ascot#First generation (CB1/2/3/4)|Honda Ascot]] models (1989–1996) later upgrading to electronically controlled. General Motors offered Delphi's [[Quadrasteer]] in their Silverado/Sierra and Suburban/Yukon. Due to low demand, GM discontinued the technology at the end of the 2005 model year.<ref>{{cite web
 |url         = http://wardsautoworld.com/ar/auto_quadrasteer_off_course/
 |title       = Quadrasteer Off Course
 |first1      = Tom
 |last1       = Murphy
 |first2      = Brian
 |last2       = Corbett
 |date=2005-03-01
 |publisher   = Wards Auto World
 |access-date=2010-06-11
 |url-status     = live
 |archive-url  = https://web.archive.org/web/20110323015108/http://wardsautoworld.com/ar/auto_quadrasteer_off_course/
 |archive-date=2011-03-23
}}</ref> Nissan/Infiniti offer several versions of their [[HICAS]] system as standard or as an option in much of their line-up.

In the early 2000s, a new generation of four-wheel steering systems was introduced into the market. In 2001 BMW equipped the [[BMW 7 Series (E65)|E65 7 series]] with an all-wheel steering system (optional, called 'Integral Active Steering'), which is available on the current 5, 6, and 7 series,<ref>{{cite web|url=http://www.bmw.com/com/en/newvehicles/7series/sedan/2015/showroom/m_performance.html|title=BMW 7 Series Sedan : M Performance|last=AG|first=BMW|website=www.bmw.com|access-date=2017-04-06|url-status=live|archive-url=https://web.archive.org/web/20170406201300/http://www.bmw.com/com/en/newvehicles/7series/sedan/2015/showroom/m_performance.html|archive-date=2017-04-06}}</ref><ref>{{cite web|url=http://www.bmw.com/com/en/newvehicles/6series/coupe/2014/showroom/driving_dynamics_and_efficiency/driving_dynamics.html#c=3&t=s|title=BMW 6 Series Coupé : Driving dynamics|last=AG|first=BMW|website=www.bmw.com|access-date=2017-04-06|url-status=live|archive-url=https://web.archive.org/web/20170406214428/http://www.bmw.com/com/en/newvehicles/6series/coupe/2014/showroom/driving_dynamics_and_efficiency/driving_dynamics.html#c=3&t=s|archive-date=2017-04-06}}</ref><ref name=":1" /> as an option. Renault introduced an optional all-wheel steering called '4control'<ref name=":2">{{cite web|url=https://www.renault.co.uk/vehicles/new-vehicles/all-new-megane-sport-tourer/equipment.html|title=Feature {{!}} All-New MEGANE Sport Tourer {{!}} Cars {{!}} Renault UK|website=Renault|language=en-GB|access-date=2017-04-06|url-status=live|archive-url=https://web.archive.org/web/20170406211740/https://www.renault.co.uk/vehicles/new-vehicles/all-new-megane-sport-tourer/equipment.html|archive-date=2017-04-06}}</ref><ref name=":3">{{cite web|url=https://www.renault.fr/vehicules/vehicules-particuliers/talisman/equipements.html|title=Equipements {{!}} Talisman {{!}} Véhicules Particuliers {{!}} Véhicules {{!}} Renault FR|website=Renault|language=fr-FR|access-date=2017-04-06|url-status=live|archive-url=https://web.archive.org/web/20170407053817/https://www.renault.fr/vehicules/vehicules-particuliers/talisman/equipements.html|archive-date=2017-04-07}}</ref><ref name=":4">{{cite web|url=https://www.renault.fr/vehicules/vehicules-particuliers/espace/equipements.html|title=Equipements {{!}} Espace {{!}} Véhicules Particuliers {{!}} Véhicules {{!}} Renault FR|website=Renault|language=fr-FR|access-date=2017-04-06|url-status=live|archive-url=https://web.archive.org/web/20170407054000/https://www.renault.fr/vehicules/vehicules-particuliers/espace/equipements.html|archive-date=2017-04-07}}</ref> in 2009, at first on the [[Renault Laguna|Laguna GT]], which is currently available on the [[Renault Talisman|Talisman]],<ref name=":3" /> [[Renault Mégane|Mégane]]<ref name=":2" /> and [[Renault Espace|Espace]]<ref name=":4" /> vehicle lines. In 2013, Porsche introduced a system on the [[Porsche 991|911 Turbo]] as standard equipment.<ref>{{cite web|url=http://www.porsche.com/uk/models/911/911-turbo/chassis/rear-axles-steering/|title=Porsche 911 Turbo - Rear-axle steering - Porsche Great Britain|website=Porsche Great Britain - Dr. Ing. h.c. F. Porsche AG|language=en-GB|access-date=2017-04-06|url-status=live|archive-url=https://web.archive.org/web/20170407054340/http://www.porsche.com/uk/models/911/911-turbo/chassis/rear-axles-steering/|archive-date=2017-04-07}}</ref> Since 2016, the [[Porsche Panamera|Panamera]] has been offered with optional all-wheel steering.<ref>{{cite web|url=http://www.porsche.com/uk/models/panamera/panamera/drive-chassis/rear-axle-steering/|title=Porsche The new Panamera - Rear-axle steering - Porsche Great Britain|website=Porsche Great Britain - Dr. Ing. h.c. F. Porsche AG|language=en-GB|access-date=2017-04-06|url-status=live|archive-url=https://web.archive.org/web/20170406201728/http://www.porsche.com/uk/models/panamera/panamera/drive-chassis/rear-axle-steering/|archive-date=2017-04-06}}</ref> The 2014 [[Audi Q7]] was launched with an optional system.<ref>{{cite web|url=http://www.uk.audi.com/uk/web/en/models/q7/q7.html?pid=int:audiuk:modelpages#page=/uk/web/en/models/q7/q7/equipment.html&layer=/uk/web/en/models/q7/q7/equipment.mediathek_infolayer.MHIA0N5.html|title=Audi Q7 > Audi configurator UK|website=www.uk.audi.com|language=en-CA|access-date=2017-04-06|url-status=live|archive-url=https://web.archive.org/web/20170406202934/http://www.uk.audi.com/uk/web/en/models/q7/q7.html?pid=int:audiuk:modelpages#page=/uk/web/en/models/q7/q7/equipment.html&layer=/uk/web/en/models/q7/q7/equipment.mediathek_infolayer.MHIA0N5.html|archive-date=2017-04-06}}</ref> Also the Japanese OEMs offer luxury segment vehicles equipped with all-wheel steering, such as Infiniti on its QX70 model ('Rear Active Steering')<ref>{{cite web|url=https://www.infiniti.co.uk/cars/new-cars/qx70/performance.html|title=INFINITI QX70 Specs - Performance Features & Engine Options|website=Infiniti|language=en-GB|access-date=2017-04-06|url-status=live|archive-url=https://web.archive.org/web/20170406201307/https://www.infiniti.co.uk/cars/new-cars/qx70/performance.html|archive-date=2017-04-06}}</ref> and Lexus on the GS.<ref>{{cite web|url=https://www.lexus.de/lexus-today/news-events/lexus-gs-2016.html#|title=News&Events, Neuigkeiten|website=www.lexus.de|language=de-DE|access-date=2017-04-06|url-status=dead|archive-url=https://web.archive.org/web/20170222054646/https://www.lexus.de/lexus-today/news-events/lexus-gs-2016.html|archive-date=2017-02-22}}</ref> Italian manufacturers have launched the technology in the model years 2016–17 with the [[Ferrari F12tdf]],<ref>{{cite web|url=http://auto.ferrari.com/en_EN/sports-cars-models/car-range/f12tdf/#innovations-dynamics-4|title=Ferrari F12tdf: Track-Level Performance on the Road - Ferrari.com|website=Ferrari GT - en-EN|language=en-US|access-date=2017-04-06|url-status=dead|archive-url=https://web.archive.org/web/20170407053832/http://auto.ferrari.com/en_EN/sports-cars-models/car-range/f12tdf/#innovations-dynamics-4|archive-date=2017-04-07}}</ref> the [[Ferrari GTC4Lusso]]<ref>{{cite web|url=http://gtc4lussot.ferrari.com/en/comfort/dynamic|title=GTC4LUSSO T: maximum control for a unique driving experience|website=GTC4Lusso T|language=en-GB|access-date=2017-04-06|url-status=live|archive-url=https://web.archive.org/web/20170407053738/http://gtc4lussot.ferrari.com/en/comfort/dynamic|archive-date=2017-04-07}}</ref> as well as the [[Lamborghini Aventador|Lamborghini Aventador S]].<ref>{{cite web|url=https://www.lamborghini.com/en-en/models/aventador/aventador-s-coupe|title=Lamborghini Aventador S Coupé|website=www.lamborghini.com|language=en|access-date=2017-04-06|url-status=live|archive-url=https://web.archive.org/web/20170425024942/http://www.lamborghini.com/en-en/models/aventador/aventador-s-coupe|archive-date=2017-04-25}}</ref>

{{Gallery
|width=180 | height=170
|align=center
|File:Caldwell vale tractor.jpg|Early example of four-wheel steering. 1910 photograph of 80 hp [[Caldwell Vale]] tractor in action.
|File:Mercedes Kübelwagen G5.jpg|1937 Mercedes-Benz Type G 5 with four-wheel steering.
|File:Quadrasteer61.jpg|Sierra Denali with [[Quadrasteer]], rear steering angle.
|File:Arnhem-Trolleybus-4-wheel-steering.jpg|[[Articulated vehicle|Articulated]] Arnhem [[trolleybus]] demonstrating its four-wheel steering on front and rear axles (2006).
|File:Honda Prelude Mk III rear steering box.jpg|Honda Prelude Mk III rear steering box
}}

=====Crab steering=====
Crab steering is a special type of active four-wheel steering. It operates by steering all wheels in the same direction and at the same angle. Crab steering is used when the vehicle needs to proceed in a straight line but at an angle: when changing lanes on a highway at speed, when moving loads with a reach truck, or during filming with a camera dolly.

Rear wheel steering can also be used when the rear wheels may not follow the path taken by the front wheel tracks (e.g. to reduce soil compaction when using rolling farm equipment).

{{Gallery
|width=180 | height=170
|align=center
|File:Bauma 2007 Telescopic Handler Liebherr 2.jpg|2007 Liebherr-Bauma [[telescopic handler]] using crab steering.
|File:HAMM DV70 Tandemwalze im Hundegang.jpg|Hamm DV70 tandem roller using crab steering to cover maximum road surface (2010).
|File:Slurry applicator - geograph.org.uk - 1252279.jpg|Agricultural slurry applicator using crab steering to minimise soil compaction (2009).
}}

===={{anchor|passive}} Passive rear-wheel steering====
Many modern{{Clarify timeframe|date=July 2021}} vehicles have passive rear-wheel steering. On many vehicles, when cornering, the rear wheels tend to steer slightly to the outside of a turn, which can reduce stability. The passive steering system uses the lateral forces generated in a turn (through suspension geometry) and the [[Bushing (isolator)|bushings]] to correct this tendency and steer the wheels slightly to the inside of the corner. This improves the stability of the car through the turn. This effect is called compliance [[understeer]]; it, or its opposite, is present on all suspensions. Typical methods of achieving compliance understeer are to use a [[Watt's linkage|Watt's link]] on a live rear axle, or the use of toe control bushings on a [[Twist-beam rear suspension|twist beam suspension]]. On an [[independent rear suspension]] it is normally achieved by changing the rates of the rubber bushings in the suspension. Some suspensions typically have compliance [[oversteer]] due to geometry, such as [[Hotchkiss drive|Hotchkiss live axles]], semi-trailing arm IRS, and rear twist beams, but may be mitigated by revisions to the pivot points of the leaf spring or trailing arm, or additional suspension links, or complex internal geometry of the bushings.

Passive rear-wheel steering is not a new concept, as it has been in use for many years,{{Clarify timeframe|date=July 2021}} although not always recognized as such.