Inmotorsport, theracing setup,car setup orvehicle setup is the set of adjustments made to the vehicle in order to optimize its behaviour (performance,handling, reliability, etc.) 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 theengine, 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.
Usually adjustable vehicle parts includeshock absorbers andanti-roll bar (suspension),gear ratios anddifferential,tyre pressures and type,wing angles, wheeltoe andcamber angle,brake bias,steering lock andride height.
The following trends will apply in most cases, but there can be exceptions to some of these. Generally changes should be made one at a time, in small steps. Adjusting to gain in one characteristic will often will often be at the expense of another characteristic.[1]
| Component | Reduceundersteer | Reduceoversteer |
|---|---|---|
| Weight distribution | centre of gravity towards rear | centre of gravity towards front |
| Frontshock absorber | softer | stiffer |
| Rear shock absorber | stiffer | softer |
| Frontsway bar | softer | stiffer |
| Rear sway bar | stiffer | softer |
| Fronttyre selection1 | largercontact area² | smaller contact area |
| Rear tyre selection | smaller contact area | larger contact area² |
| Front wheel rim width or diameter (will change the tireshape but not area) | larger² | smaller |
| Rear wheel rim width or diameter (will change tireshape, but not area) | smaller | larger² |
| Front tyre pressure* | lower pressure | higher pressure |
| Rear tyre pressure* | higher pressure | lower pressure |
| Front wheelcamber | increase negative camber | reduce negative camber |
| Rear wheel camber | reduce negative camber | increase negative camber |
| Rearspoiler | smaller | larger |
| Front height (because these usually affect camber androll resistance, see alsobody roll; not to be confused withrolling friction) | lower front end | raise front end |
| Rear height | raise rear end | lower rear end |
| Fronttoe in | decrease | increase |
| Rear toe in | decrease | increase |
| 1) tyre contact area can be increased by using wider tyres, or tyres with fewer grooves in the tread pattern. Of course fewer grooves has the opposite effect in wet weather or other poor road conditions. 2) These also improveroadholding, under most conditions. * Actually every tyre has its "optimum" pressure at which it makes the most grip. Above this grip slowly drops and below this it drops quickly. Just keep this in mind so that if you find dropping pressure improves that end of the car or adding pressure lowers it. | ||
In addition, lowering the centre of gravity will always help the handling (as well as reduce the chance of roll-over). This can be done to some extent by using plastic windows (or none) and light roof, hood (bonnet) and boot (trunk) lid materials, by reducing the ground clearance, etc. Increasing the track with "reversed" wheels will have a similar effect, but remember that the wider the car the less spare room it has on the road and the farther you may have to swerve to miss an obstacle. Stiffer springs and/or shocks, both front and rear, will generally improve handling, at the expense of comfort on small bumps. Performance suspension kits are available. Light alloy (mostly aluminium or magnesium) wheels improve handling and ride as well as appearance.
The car's roll centre is the other fundamental piece of the equation. Care must be taken to avoid lowering the centre of gravity past the car's roll centre. The distance between the car's centre of gravity and its roll centre is known as theroll couple, or the length that the car rolls around. Ideally, if the roll centre and the centre of gravity occupy the same space, the car should exhibit zero body roll.
Moment of inertia can be reduced by reducing weight, usually results from using lighter bumpers and wings (fenders), or none at all.