spring perch holes

[Chucksdart]

Got some weld on spring perches from Mancini. The holes for the alignment pin is larger than the pin itself. Should I make a bushing to shim this up ? Or is it O.K. like this? The hole in the stock perch is the same size as the button on the leaf springs.

[cutting torch]

I would leave them alone, and use them to correct the thrust line to the centerline of the car. After that is set, you can tack weld a washer to the perch, so you can remove the axle later without changing it's location.

torch

[Chucksdart]

Thanks Torch, What's this all about? Sounds like something I should learn about. Could ya help educate a dummy on the torque line adjustment? Like how to do it , and why?

[cutting torch]

The thrust line is perpendicular to your axle, and is the direction it wants to travel. Ideally, this should line up with the centerline of your car. That would make all 4 wheels run parallel, with each side tracking in-line side to side. If your thrust line is off, you can still align it to have all 4 wheels parallel, but they won't track the same line side to side, which in severe cases can make it "dog-track".

torch

[cutting torch]

Sorry, you asked how. I can't tell you that. A good buddy of mine does alignments, and has educated me a lot. I understand most of the theories and know plenty about it, but I have never put a car on an alignment rack. I'm sure some one can enlighten both of us on that, and/or tell me I'm full of sh*t!

torch

[pishta]

Found this article on a 4X4 site:

The thrust angle is defined as the deviation between the bisector of the total rear toe angle of the vehicle (the thrust line) and the vehicle centerline.

This is a tad more complicated than is sounds.. the centerline of the vehicle is defined NOT by the axle midpoints, but rather by the position of each of the vehicle wheels. In an extreme example, imagine a car which is narrower in the front than in the rear. If you draw lines connecting the tires on the left side of the car (front & rear) and the tires on the right side of the car (front and rear), the lines will intersect at some point in space out infront of the car. Bisect the angle formed by the intersection of these lines, and you will have the centerline of the vehicle's wheel system. Usually this is very close to the chassis centerline (as measured by the axle midpoints), but it's not exactly the same.

Next, to determine the total rear toe angle, the toe angle for each rear wheel is determined relative to the wheel system centerline. The sum of these angles is the total rear toe angle. If you project lines parallel to the face of each rear wheel, the two lines will intersect somewhere at a point unless the wheels are exactly parallel to each other. The angle at which these lines intersect is the total rear toe angle. Bisecting this angle with a line yields the thrust line of the vehicle. This is the direction the two rear wheels of the vehicle would travel if allowed to just roll along.

Finally, the angle measured between the vehicle's wheel system centerline (as determined by the position of all four wheels) and the thrust line of the vehicle (determined by the pointing direction of the rear wheels) is measured as the thrust angle.

[Rods67Cuda]

when i redid my rear ( installed a 3.91 clutch type suregrip 489 case ), I went ahead and pulled the housing and stripped/painted it, and disassembled the springs....
i also put in the offset hanger kit, so i got new perches, and had the same situation....
I made my own pins, since i disassembled the springs for cleaning/repaint anyway....that way i could make them to fit AND they'd be new (the originals were badly corroded)