Kingpin angle is the angle of the line drawn through the upper and lower ball joint, compared to vertical if you were looking at the suspension from the front. That doesn't sound like what you're looking for, but as I said I'm having trouble following without a picture.

 

He is talking about Kingpin angle. There are lots of various terms for this angle. Caster is the angle of these two ball joints when viewed from the side of the car, kingpin angle is the angle of these two ball joints when viewed from the front of the car. FYI: Scrub radius is the difference between this line extended to the ground and the center of the tire contact patch. As scrub radius increases, the amound of load put into the steering wheel increases while braking on uneven or mis-matched surfaces.

It's not adjustable, other than it changing as you change camber due to the lower balljoint moving in and out. They don't match perfectly side-to-side even on new cars. If it's out and both wheels are set to the same camber number, the hub/knuckle is likely bent.

 

After rereading his description I think you're right, it is kingpin angle.

I have no idea how you'd measure this though to that much precision, since this isn't a formula car, so my question still stands - how was it measured? If you can describe that then maybe someone can measure it and see what it is. I bet it will be tough since it has to be at ride height.

Also wouldn't our ride height have to match yours, or we'd get different numbers? Maybe it won't change that much, I'm not sure.

 

8 to 12 degrees of lateral kingpin angle seems excessive, that's more than the longitudinal kingpin angle (caster) but I've never attempted to measure it.

 

It's measured the same way as Caster. The machines look at how the camber changes as it rotates about the axis and does the fancy math to figure it out.

 

I agree! This is measured and adjusted at alignment as it efects camber on our cars.

 

thanks for the input guys

does any body now what the kingpin angle is for a stock AP1 is ?

just wandering which side is not OK (maybe damaged ?)
if I have 8° on one side and 12° on the other...

 

<div></div><div>Most modern suspensions don't have an actual kingpin, but the kingpin angle on the S2000 is a line drawn between the knuckle's upper and lower ball joint pivots. The kingpin angle will change when the camber and caster adjusters are moved. The caster adjuster changes longitudinal kingpin angle--what we call caster. The camber adjuster changes the lateral kingpin angle. In our car we add negative camber by moving the lower control arm outward which will increase the lateral kingpin angle you're asking about. I've never seen a value for that angle so I don't know if 8 or 12 degrees is more nominal.<div>

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I think you're talking about steering axis inclination(SAI). you can also set both adjustments to caster and camber to a max position to get a better measurement of SAI. Because it's always different if either side has a height(coilovers), weight, camber, and caster difference. You cannot adjust for SAI on an alignment rack, it just changes with the alignment


and if i remember correctly, to calculate SAI use this:

.75/tan(X-Y)

x=from ball joint to wheel center(hub face)
y=from ball joint to wheel base(actual wheel, not including tire)

if x or y is different on either side, it will tell you more if something is bent if camber and caster is maxed. but you're still shooting blind since no one has a perfect off the lot s2k that you can measure to get a known good measurement

 

the car's suspension has now been fully rebuilt with Spoon bushing and the nitron shocks overhauled
settings as below + corner weighting

front Caster Left 5°20 «
Caster Right 5°15 « (max possible)
Camber Left -1°20 «
Camber Right -1°20 « (max possible)
Toe Left 0°00 «
Toe Right 0°00 «
Total Toe 0°00 «



rear Camber Left - 2°30 «
Camber Right - 2°30 «
Toe Left + 0°20 «
Toe Right + 0°10 «
Total Toe + 0°10 «

and so with these settings there's 11°26' kingpin angle on the left and 7°41' on the right.. the question being : which side has a problem ?