King Pin Inclination Angles
By Middo on Thursday, 29 August 2024
Posted in Technical
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Does anyone have any experience with King Pin Inclination angles for front steering?

My research suggests the King Pins on the Alpha P2 where around 9 degrees in camber (top of pin towards the car) and 8 degrees in caster (Top of pin to the rear).

While this might have given the original car good stability at speed, I am a bit concerned that these angles are excessive (especially since some cyclekarts are built 0,0) and while it may be stable it might not be real nimble and make it less fun in that respect.

Anyone built a setup they are happy with?

See Table Below

Racecar Model Forward-Aft KPI (degrees) In-Out KPI (degrees)
Alfa Romeo P2 7-9 8-10
Bugatti Type 35 8-10 9-11
Mercedes-Benz W25 6-8 7-9
Auto Union Type C 7-9 8-10
Maserati 8CM 7-9 8-10
Delage 15 S8 8-10 9-11
King pin inclination (KPI) along with caster (which you describe as forward-aft KPI) help to provide steering self centering and therefore stability. With a near zero inclination and caster angle the steering will be very light and twitchy, and you will find that bumps and ruts in the road will have a negative effect on handling, as the cyclekart will tend to dart around and be very lively.

By adding KPI and caster the natural tendency of the steering is that the weight of the car will push the wheels back to their centred position. Bumps and ruts will have much less of a negative impact as any displacement of the wheels is automatically corrected, but steering will be much heavier.

The figures that you have quoted seem fairly typical and are a reasonable guide. Some run as much as 15 degrees KPI.

However it should be considered that King pin inclination and caster alone do not completely define the handling as there are additional factors such as Ackerman angle and scrub radius that also influence handling characteristics.

HTH
Mick
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2 months ago
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