Editing Automobile handling (section)

=== Weight distribution ===
{{Main|Weight distribution}}

==== Centre of mass height ====
The [[centre of mass]] height, also known as the centre of gravity height, or CGZ, relative to the track, determines [[load transfer]] (related to, but not exactly [[weight transfer]]) from side to side and causes body lean. When tires of a vehicle provide a [[centripetal force]] to pull it around a turn, the [[momentum]] of the vehicle actuates load transfer in a direction going from the vehicle's current position to a point on a path [[tangent]] to the vehicle's path. This load transfer presents itself in the form of body lean. In extreme circumstances, the vehicle may [[Vehicle rollover|roll over]].

Height of the centre of mass relative to the wheelbase determines load transfer between front and rear. The car's momentum acts at its centre of mass to tilt the car forward or backward, respectively during braking and acceleration. Since it is only the downward force that changes and not the location of the centre of mass, the effect on over/under steer is ''opposite'' to that of an actual change in the centre of mass. When a car is braking, the downward load on the front tires increases and that on the rear decreases, with corresponding change in their ability to take sideways load.

A lower centre of mass is a principal performance advantage of [[sports car]]s, compared to sedans and (especially) [[SUV]]s. Some cars have body panels made of lightweight materials partly for this reason.

Body lean can also be controlled by the springs, [[anti-roll bar]]s or the [[roll center]] heights.
{| class="wikitable" style="margin: 1em auto; text-align: center;"
|+ List of car [[Center of Gravity]] heights
|-
!| Model
!| Model<br>year
!| CoG height
|- <!--if too many entries, suggest reduction by notability; numbers made and extremes of height-->
| [[Ram Pickup#First generation .281981.E2.80.931993.3B D.2FW.29|Dodge Ram B-150]]<ref name=nhtsa1999>Gary J. Heydinger et al. "[http://1985mustanggt.com/Reference/sae1999-01-1336.pdf Measured Vehicle Inertial Parameters - NHTSA's Data Through November 1998] {{webarchive|url=https://web.archive.org/web/20160630121744/http://1985mustanggt.com/Reference/sae1999-01-1336.pdf |date=2016-06-30 }}" page 16+18. ''[[National Highway Traffic Safety Administration]]'', 1999</ref>
| 1987
| {{convert|85|cm|in|abbr=out|0}}
|-
| [[Chevrolet Tahoe]]<ref name=nhtsa1999/>
| 1998
| {{convert|72|cm|in|abbr=out|0}}
|-
| [[Lotus Elise]]<ref>{{cite web|date=2014-02-04|title=Suspension|url=http://willmartin.com/suspension/|url-status=live|archive-url=https://web.archive.org/web/20160625121424/http://willmartin.com/suspension/|archive-date=2016-06-25|access-date=2016-06-05|quote=The Lotus Elise has a kinematic roll center height of 30mm above the ground and a centre of gravity height of 470mm [18½"]. The Lotus Elise RCH is 6% the height of the CG, meaning 6% of lateral force is transferred through the suspension arms and 94% is transferred through the springs and dampers.}}</ref>
| 2000
| {{convert|47|cm|in|abbr=out|0}}
|-
| [[Tesla Model S]]<ref name=rope>{{cite web |first=L. David |last=Roper |url=http://www.roperld.com/science/TeslaModelS.htm |title=Tesla Model S Data |access-date=2015-04-05 <!--sources at page bottom--> |archive-date=2019-09-11 |archive-url=https://web.archive.org/web/20190911155446/http://www.roperld.com/science/teslamodels.htm |url-status=live }}</ref><ref name=sciAbuild>{{cite web |url=http://www.scientificamerican.com/article/how-tesla-motors-builds-the-safest-car-video/ |title=How Tesla Motors Builds One of the World's Safest Cars [Video] |author=David Biello |work=Scientific American |access-date=2016-06-06 |archive-date=2018-11-07 |archive-url=https://web.archive.org/web/20181107011527/https://www.scientificamerican.com/article/how-tesla-motors-builds-the-safest-car-video/ |url-status=live }}</ref>
| 2014
| {{convert|46|cm|in|abbr=out|0}}
|-
| [[Chevrolet Corvette (C7)]] Z51<ref>{{cite web|url=http://www.caranddriver.com/comparisons/2014-chevrolet-corvette-stingray-z51-page-3|title=2014 Chevrolet Corvette Stingray Z51|date=1 November 2013|access-date=6 June 2016|quote=Its center-of-gravity height—17.5 inches—is the lowest we've yet measured|archive-date=1 January 2018|archive-url=https://web.archive.org/web/20180101082404/https://www.caranddriver.com/comparisons/2014-chevrolet-corvette-stingray-z51-page-3|url-status=live}}</ref>
| 2014
| {{convert|44.5|cm|in|abbr=out|0}}
|-
| [[Alfa Romeo 4C]]<ref>{{cite web|url=http://www.caradvice.com.au/253053/alfa-romeo-4c-review/|title=Alfa Romeo 4C Review|work=CarAdvice.com.au|author=Connor Stephenson|date=24 September 2013|access-date=6 June 2016|quote=the centre of gravity is just 40cm off the ground|archive-date=24 August 2018|archive-url=https://web.archive.org/web/20180824183429/https://www.caradvice.com.au/253053/alfa-romeo-4c-review/|url-status=live}}</ref>
| 2013
| {{convert|40|cm|in|abbr=out|0}}
|-
|Formula 1 Car
|2017
|25 centimetres (10&nbsp;in)
|}

==== Centre of mass ====
In steady-state cornering, front-heavy cars tend to [[understeer]] and rear-heavy cars to oversteer [[Understeer and oversteer|(Understeer & Oversteer explained)]], all other things being equal. The [[mid-engine design]] seeks to achieve the ideal center of mass, though front-engine design has the advantage of permitting a more practical engine-passenger-baggage layout. All other parameters being equal, at the hands of an expert driver a neutrally balanced mid-engine car can corner faster, but a FR (front-engined, rear-wheel drive) layout car is easier to drive at the limit.

The rearward weight bias preferred by sports and racing cars results from handling effects during the transition from straight-ahead to cornering. During corner entry the front tires, in addition to generating part of the lateral force required to accelerate the car's [[centre of mass]] into the turn, also generate a torque about the car's vertical axis that starts the car rotating into the turn.  However, the lateral force being generated by the rear tires is acting in the opposite torsional sense, trying to rotate the car out of the turn. For this reason, a car with "50/50" weight distribution will understeer on initial corner entry. To avoid this problem, sports and racing cars often have a more rearward weight distribution. In the case of pure racing cars, this is typically between "40/60" and "35/65".{{Citation needed|reason = Contemporary F1, Le Mans, and Cup cars are all between 50/50 and 40/60|date=July 2010}} This gives the front tires an advantage in overcoming the car's [[moment of inertia]] (yaw angular inertia), thus reducing corner-entry understeer.

Using wheels and tires of different sizes (proportional to the weight carried by each end) is a lever automakers can use to fine tune the resulting over/understeer characteristics.

==== Roll angular inertia ====
This increases the time it takes to settle down and follow the steering. It depends on the (square of the) height and width, and (for a uniform mass distribution) can be approximately calculated by the equation:  <math>I=M(height^2+width^2)/12</math>.<ref>{{cite book|title=Engineering Mechanics 3|publisher=Springer|doi=10.1007/978-3-642-30319-7|year=2013|isbn=978-3-642-30318-0|last1=Gross|first1=Dietmar|last2=Hauger|first2=Werner|last3=Schröder|first3=Jörg|last4=Wall|first4=Wolfgang A.|last5=Rajapakse|first5=Nimal}}</ref>

Greater width, then, though it counteracts center of gravity height, hurts handling by increasing angular inertia. Some high performance cars have light materials in their fenders and roofs partly for this reason

==== Yaw and pitch angular inertia (polar moment) ====
Unless the vehicle is very short, compared to its height or width, these are about equal. Angular inertia determines the [[rotational inertia]] of an object for a given rate of rotation. The [[Yaw angle|yaw]] angular inertia tends to keep the direction the car is pointing changing at a constant rate. This makes it slower to swerve or go into a tight curve, and it also makes it slower to turn straight again. The [[Pitch (flight)|pitch]] angular inertia detracts from the ability of the suspension to keep front and back tire loadings constant on uneven surfaces and therefore contributes to bump steer. Angular inertia is an integral over the ''square'' of the distance from the center of gravity, so it favors small cars even though the lever arms (wheelbase and track) also increase with scale. (Since cars have reasonable symmetrical shapes, the off-diagonal terms of the angular inertia [[tensor]] can usually be ignored.) Mass near the ends of a car can be avoided, without re-designing it to be shorter, by the use of light materials for bumpers and fenders or by deleting them entirely. If most of the weight is in the middle of the car then the vehicle will be easier to spin, and therefore will react quicker to a turn.