Castor or Caster angle


Castor angle representation

Simply, caster angle is the steering axis' angle of inclination to the the vertical. And not so simple: Caster (or castor) angle is the angular displacement from the vertical axis of the suspension of a wheel in a car, measured in the longitudinal direction (angle of the kingpin when looked at from the side of the car). This can be relatively easy to spot on a single seater racing car as the push/pull rod is exposed and can be clearly seen the angle between the upper and lower wishbone pickup points on the wheel hub. The angle at which it is leant back or forward provides a rough indicator of how much caster angle the car has, as it has to squeeze through the gaps in the wishbones from the base of the hub to reach the chassis.

It is the angle between the pivot line (in a car - an imaginary line that runs through the center of the upper ball joint to the center of the lower ball joint) and vertical. Caster angle can be adjusted to optimize a car's handling characteristics for particular driving situations.

The pivot points of the steering are angled in a way that a line drawn through them intersects the road surface slightly ahead of the contact point of the wheel. The purpose of this is to provide a degree of self-centering for the steering - the wheel casters around so as to trail behind the axis of steering. This makes a car easier to drive and improves its straight line stability (reducing its tendency to wander).

Improper adjustment will result in steering inputs required both into and out of a corners, resulting in a car which is difficult to keep on a straight line.  Too much caster (positive caster) and the front of the car will understeer more, too little (negative caster) and you will get oversteer handling characteristics. A large positive camber setting (wheel facing forward of axis) is good for high speed stability but can make it more difficult for turning the steering, excessive amounts will increase tire wear.
Excessive caster angle will make the steering heavier and less responsive, although, in off-road racing, large caster angles are used to improve camber gain in cornering.

All F1 cars run with at least a few degrees of positive caster angle – as far as I am aware there is no need to use a negative angle – and in some cases it can be over 10 degrees. The reason for this is, as I explained before, that it has a strong self-centering effect on the steering as torque is applied. The higher the angle the more self-centering the steering feels.

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Some useful links:

- f1technical.net, a great site with a lot of technical information’s and explanations. Site is updated daily with news from F1 word.

 - autosport.com, This site is a legend. A bible for racing lovers. News from all around the word. Unfortunately, to get access to all news, interviews and to open the site completely you should be subscribed to Autosport magazine. Anyway, great read.

James Allen on F1
- JA.F1 site (or blog) ovned by ITV Sport’s lead commentator on Formula 1 James Allen

Joe Saward blog
- joesaward is the Joe Saward official blog about Formula 1 world. Joe is an journalist, who write primarily about politics in and around motorsport, specifically on the FIA Formula 1 World Championship

Vital F1
 - vitalf1.com/ is another great site for Motor Sports fan’s like me. Site is relatively new, but great fun, with great discussion forum, Formula 1 news and forum.

 GP update
- f1.gpupdate.net, Site with fresh news from Formula 1

Planet F1
 - planetf1, another site with many different articles, news and statistics. Biased toward British teams, but anyway good read.

Gurney flap
 - gurneyflap.com, Great history site. You can learn a lot from this site. Pictures, cars and many many more. Great.

4ormula1 is a database of Formula 1 history and statistics of drivers, teams, grand prix, and all results since 1950.

Missed Apex Podcast
Enjoy range of Podcasts and Articles on Motorsport. Every week a Formula one chat on Missed Apex F1 Podcast with F1 journalist Joe Saward and tech Analyst Matthew Somerfield as guests. Also the exciting all electric racing series formula E on eRadio Show and Bike Show Lean Angle Podcast.

Racecar engineering
-Racecar Engineering, an online magazine with a lot to learn from, a lot of technical information’s and explanations

 - fia.com, La Fédération Internationale de l'Automobile, representing the interests of motoring organisations and motor car users. Head organisation and ruler in auto sport.

 - wikipedia.org, I don’t believe that I have to tell you anything about this site. It’s not about Formula 1 technology, but you can learn a lot about that too.

Sutton Images

grandprix photo

 - carbibles.com, a great site for normal car users. Here you can find explanations of almost everything about your car and how it works. Technical reviews and explanations of some in-car gadgets.

Dare To Be Different
- Daretobedifferent.org Susie Wolff and UK governing body of UK motorsport have joined forces to launch Dare To Be Different, a high-profile new initiative which is about increasing female participation, not just on the track but in all aspects of the sport.

Giorgio Piola web site