Rear tires diagonal scuffing
#21
08-17-2012, 12:09 PM
Camber is set around 1-1.5 negative thus creating a problem. It doesnt even have to be a lowered car, just a car with a bunch of crap in the back that makes the rear of the car sag (we've all seen it) If the camber is 0 then yes there will be no toe change. The problem is the rear wheels dont go straight up and down in its travel it arcs along the path of the rear beam radius. So if there is any camber that will slowly be translated to toe the more the beam travels up.
The rear axle is fixed to rotate longitudially and the arm and hub are ridgid. When the axle is rotated as the arms are raised there in no change in the hub location and therefore no change in the toe. As the arm is raised there is a change in camber but unless the arm on one side is raised more than the other as when the axle twists in torsion there is no change in toe. That twist unaligns the axle so that it is then two distinct units and one moves indeopendent oif the other and not parallel.
Bend a coat hanger wire to match the axle, arms, and hubs and see for yourself. The attachment point for the shock swings out and camber changes but not the toe. If the hub were fastened to the shock base then both camber and toe will change.But it isn't.
#22
08-17-2012, 12:41 PM
The I beam rotates in an arc and shouldn't have an effect on camber. It was obvious that my wheels were cambering inward at the top with 7"x 15" 41 offset wheels and even more with 16"x 7" 38offset wheels.. It isn't obvious with the 16"x6 1/2" 45 offset wheels that I now have on the car.. That leads me to believe that the swing arms from the I beam to the wheels flex with wider wheels and low offset numbers.
Rotating the axle swings the arm upward ( or downward). A plate fastened parallel to the body to the end of the arm wsill change camber as the end of the arm rotates. That plate represents the hub and therefore the camber changes with the swing of the arrn.
Now attach the bar at an angle and rotate it as though it were a single wide arm. Think of it as a wide bar that attaches the vertical plate at the front and the attach to the body (frame) at the rear. Swing the wide plte up and down as the arm and follow the 'camber' of the vertical plate. When otating that arm(plate) doesn't change the toe, but camber changes a lot. As you would expect as the plate camber goes increasing negative as the 'arm' swings upward to counter cornering forces trying to fold thed tire tread away. Very simple but effective for Fits but Porsche engineers won't use it.
its the same as fastening a plate toi the end of a bar and swinging the arm up and down. just because the bar is a diagonal instead of streaight has no efeect on the 'camber' of the plate.
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