I’ve been having trouble getting much “return to center” on my front steering, and it feels a little too responsive to steering wheel input. Since I blew out my original rack and I suspected the pressure was causing resistance, I reduced the power steering pump pressure from 1000psi to 800 psi without any change in this problem. I suppose I have neglected some geometry that’s adding to the problem. I had the front end aligned professionally last year. I had an appointment for a professional inspection and analysis by an experienced chassis/wheel alignment but the man forgot to remember he had today off......maybe later this week I guess.
Today I went out and measured the car at several locations and I’m wondering how to make sense of what I’ve found:
Legend: RF = Right Front LF = Left Front RR = Right Rear LR = Left Rear
Body edge wheel well from the ground: LF = 26 1/4" RF = 27 1/4"
LR = 27 1/4" RR = 28"
I have inspected and found that the body contours meet the frame identically from side to side, so I suppose that’s not just an installation difference.
Frame Corners measured from the ground: LF = 4" RF = 4 1/4"
LR = 4 3/4" RR = 5 1/8"
Ground to bottom of front outer lower suspension arm:
LF = 7 1/2" RF = 7 1/2"
Ground to bottom of rear axle tube/housing closest to brake:
LR = 10 3/8" RR = 10 3/4"
Poor-man's alignment figures measured by me:
Camber: LF 2.4 deg neg. RF 2.4 deg. neg
Toe-in: Measured by center tread to tread comparing the front and rear measurements on the front tires with steering at midpoint:
Distance between center fronts of tires: 60"
Distance between center rears of tires: 60 3/8” (!)
They also appear toed out to visual inspection.
Caster: I understand the principle, just have no idea how to accurately measure it without some equipment I don't own, but by visual inspection it is present and significant.
The shocks are all at fullest spring extension, symmetrically mounted without spacers or differences in length.
Inspecting the changes made to the A arm attachment in the alignment process I found a 1/8” shim behind the front on the Left side and a ½” shim (wow!) behind the front on the Right side.
So, if these are anywhere close to real numbers, then it seems I have a problem with the toe-in to start with. Might a toe-out such as I have cause the front end to wander more than desired? I don't feel that happening when in a straightline cruise, but perhaps it would make a difference in the steering response?
With regard to camber, from the articles I’ve read, I understand the Mustang II front ends needed about 1/2 deg. negative camber. Might more than this tend to cause the front end to be more aggressive in turning? Might that cause a resistance to the normal tendency to return to center?.
I cruised around today and found the car to be fairly steady in a straight line with a very small tendency to drift right but then the roads here are centrally high-bermed to allow runoff so that might just be the road. On a full left or right 90 deg. turn if I let the wheel go after the turn there is some tendency to return partly toward center, but not much. Certainly a LOT less than I experience in my daily driver (which, granted, has a much longer wheelbase - (1995 Lincoln Town Car) The cobra just feels like it wants to turn right away and just keep on turning. My WCC has a 96” wheelbase.
With regard to the wheel well heights there doesn’t seem to be any asymmetry of body-on-frame installation. I don’t understand how the left and right rear axle housing heights can be so different on a solid axle car? Front tires are 265/50/15 Cooper Cobra Radials, the rears are 295/50/15's. Front tire pressure is 28 both sides, rear 30 both sides (determined by temperature readings across the tires after driving).
Well by posting this I’ve probably RE-achieved the esteemed lowest ranking in auto understanding once again…
With all that screwed up geometry, maybe it's a miracle the thing even goes straight and corners AT ALL!!
Regards to y'all and thanks for any input.
Dirk