Thanks to Edmunds for putting a car on the lift and taking these pictures.
i thought it was interesting that there are two lower ball joints on the hub or steering knuckle, whereas most cars have just a single ball pivot.
As the wheel is turned the knuckle rotates about the upper and lower pivot points. The line thru the upper and lower points is the steering axis and the inclination of that axis is related to the wheel caster.
Edmunds indicates the lower pivot as the intersection of the contol arms.
It looks to me that for rotation about two ball joints also requires a fore-aft translation of the bottom of the knuckle, effectively changing the wheel base to shorten it on the inner-side of a turn. However to do that requires a moment load about the attachment point of the control arm to the chassis. This is a thrust-like load that flexes and internally displaces the rubber bushings, as can be seen in the pictures in which the wheel is turned left and right.
There is no control arm to carry the thrust loads although it looks like there is an unused hole that was drilled for one in the bottom knuckle plate.
i predict that over time a shimmy will become manifest upon braking--a high frequency oscillation of the steering wheel that is quite startling when it occurs.
i thought it was interesting that there are two lower ball joints on the hub or steering knuckle, whereas most cars have just a single ball pivot.
As the wheel is turned the knuckle rotates about the upper and lower pivot points. The line thru the upper and lower points is the steering axis and the inclination of that axis is related to the wheel caster.
Edmunds indicates the lower pivot as the intersection of the contol arms.
It looks to me that for rotation about two ball joints also requires a fore-aft translation of the bottom of the knuckle, effectively changing the wheel base to shorten it on the inner-side of a turn. However to do that requires a moment load about the attachment point of the control arm to the chassis. This is a thrust-like load that flexes and internally displaces the rubber bushings, as can be seen in the pictures in which the wheel is turned left and right.
There is no control arm to carry the thrust loads although it looks like there is an unused hole that was drilled for one in the bottom knuckle plate.
i predict that over time a shimmy will become manifest upon braking--a high frequency oscillation of the steering wheel that is quite startling when it occurs.