Toe in toe out???

[Duncan]

can someone please explain the KPI angle? i believe it stands for King Pin Inclination but that is all i know!

ahh well while we are swapping half informed opinions here is mine.

On a car with properly designed double wishbone suspension the KPI should be straight, that is the point of such a complex suspension design. The issue is with cars with a strut suspension like a S13 or R31

/end uninformed opinion

[dangerous_daveo]

ahh well while we are swapping half informed opinions here is mine.

On a car with properly designed double wishbone suspension the KPI should be straight, that is the point of such a complex suspension design.  The issue is with cars with a strut suspension like a S13 or R31

/end uninformed opinion

I've got s13 suspension if that makes any difference to any of the above advice/conversation (as in the whole thread).

[blind_elk]

yeap hes correct, the castor rod goes from the lower control arm to its mount further forward, shortening it will move the wheel forward for more castor

Except in cars like the 240 / 260Z, where the castor rods go backwards, so you need to lengthen it to dial in more castor.

For Greg, just reading up on KPI in Alan Staniforth's "Competition Car Suspension".

"...the original parts, which took the form of a piece of round bar, some 4 or 5 inches long and 1/2 - 3/4 inch diameter, gripped by heat or some sort of cotter in each end of a beam axle. The hub was given 2 bronze bushes on which it pivoted around the pin to give steering movement to the front wheels....

...the angle of the pin was so arranged that a line drawn through it intersected the centre line of the tyre on the ground.

The KPI is measured in relation to the centre vertical plane of the car, ie angling from middle to outside (as distinct from rear to front). You could consider the inclination of a strut to be equivalent (from top mount outwards towards the wheel), in that a line drawn down the axis of the strut should strike the ground at the centre point of the tyre.

[Greg]

thanks for replies

blind_elk - that makes sense, thank you.