Spindle King Pin Angle

Can someone explain the correlation of why you would want to use a 10 deg spindle or a 12 deg spindle. Also just so I am understanding the angle correctly, is that the angle of the shaft from the king pin?

I see where they say some karts are built with a 10 or 12 and trying to get a grip on why and what it is.

I think what you are talking about is the spindle rake. It’s the angle built into the spindle itself from the centerline of the kingpin bolt to the spindle.

This angle combined with the angle of the kingpin itself is what makes up the caster angle.

Hmmm, I think they are talking about the angle of the spindle to the kingpin (the angle at which the spindle is welded to the body of the stub axle) which in the dead ahead position would be more or less camber. So 12 degrees would be more positive camber then 10 degrees.

Now the reason that’s different then just moving the caster camber kit to give you more camber is it doesn’t effect the king pin inclination. King pin inclination (inward lean of the king pins) modifies the amount of front wheel height change as the steering is turned, decreasing the rise of the outside front and increasing lowering of the inside front. What happens here is the majority of the jacking effect is coming from your inside front, and much less from you outside front. Whenever you adjust camber the KPI will also change (+neg camber = less KPI and +pos camber = more KPI), unless you change the spindles.

KPI is what The OP is asking about. It is the fixed angle the spindle and axle shaft is welded to. KPI cannot change as it is fixed (welded). If you have A set camber (or caster), KPI can not be changed when changing caster,camber unless you change the spindle assembly. A 10 deg will will change your weight jacking less as you turn your kart the A 12 deg spindle. It is for the most part built to suite your chassis. if it was built with 10 ,that’s what you use. there are different roads taken for A manufacture to decide what they use. As A general rule of thumb for me Ive seen more CIK style karts work better with 12 and American laydowns(goldcup) work better with 10. This is not to say one cant make the other work, but for the chassis and setups ive driven this has been the case. Now ill skip scrub for this discussion because I think that is also a MAJOR PLAYER In this discussion also.

Sorry totally disagree. Its in the name King Pin Inclination. Its the inclination of the king pin.


The angle of the spindle to the stub axle (the welded part) as far as I know doesn’t have name, lets say inclusive angle. By altering the inclusive angle you change the scrub radius without effecting the KPI.

I’m interested in the difference between the laydowns and CIK, CIK have a ton of caster built in, I always assumed laydowns did not, and I assumed (having never seen a laydown run) that they don’t jack the wheel up a huge amount like a cik kart. Having a larger scrub radius and less caster supports that.

Disclaimer: I got the image from google. 10 degrees being the optimal is not my opinion.

I’m also struggling to understand how something that doesn’t affect the kingpin’s angle is related to KPI.

Did you find out anything from the manufacturer @Don_Westlie?
In (very) simple terms, you can consider the higher degree spindle to offer more mechanical jacking.

Ok so maybe im misunderstanding what we are trying to accomplish. Kpi setting stamped on I thought the angle the king pin is welded to the stub. So if your stub is level(0 deg of camber) the king pin is leaned in at 10 degrees. Caster rotates around whatever the king pin set. So if you take a 10 off and put A 12 on, you have to readjust camber to set it the same as it was before. But most chassis do not have that wide of adjustment on there chassis. When i say laysown im talking gold cup big nose sprints. Not roadrace laydowns.

Acording to your picture im using the wrong terminolgy i guess.