i havent been here in a while and just wanted to ask about alignment of my rear.....years ago i mini tubbed and did the move the springs inboard 3 inches and just realized its out of wack....last sept i went to the track and my driverside slick grew and rubbed on the front of my fenderwell.....so i took some measurements from wheel to wheel and came up with 3/4 of an inch forward on the drivers side compared to the passenger side.....i was talking with a buddy and he said to get a better measurement was to take it off the torsion bar frame mounting.....what do you think??
thanks dave.....thats what i was going to do for the fix
Posted By: ProStDodge
Re: rear end alignment - 10/03/10 08:06 PM
Actually, you need to find the suspension centerline, which is a measurement from the pivot points of the suspension at all four corners of the car.
I will try to explain how to find a centerline for the suspension system. This can also be found in the door-slammer chassis book by Dave Morgan.
Raise the car high enough you can get under it easily - since we will be working with the suspension pivot points, it doesn't matter if the supports are under frame or the suspension. Try to keep the car level.
First, find the "center" of the car. Use a string and plumb-bob to transfer these points to the floor. On the back of the car, hang the string from the leaf spring front bolt. Doesn't matter if its the inside or outside of the spring, as long as you do the same on both sides. (on 4-link or ladder bars, use the front hiem joint)
Lower the Plumb-bob to the floor and make a mark (black sharpie worked best). Repeat for the other side. Measure the distance between the two points on the floor and mark the center. Measure 2-3 times if necessary to get it accurate.
Move to the front of the car. Hang the string off the pivot bolt on the lower control arm. Again front or back, inside or outside doesn't matter as long as you use the same point on both sides. Mark the floor directly below these points. Measure between them and mark the center.
Using a chalk line, snap a line from front bumper to back bumper across the two center points. You now have the exact center of the suspension system. Using the plumb-bob you can now measure the distance of anything on the car from the center line. Hopefully the ends of the axles are even, but points on the body will probably be off some. I like to use the front of the brake register on the axle.
Now we need a line perpendicular to the centerline to be able to measure whether the suspension parts are square with the suspension centerline as well as centered.
Using a piece of string about 3 feet long, tie one end to the marker, hold the other end on the center line near the center of the car. Mark an arc or semi circle (which extends to both sides of the car. Move the string down the centerline about a foot one way or the other and make an arc in the opposite direction). These two arcs should cross near the outside of the car. Span the chalk line over the two intersection points and you should have a precise perpendicular line.
Now you can measure front to back from the perpendicular line to the rear axles and front rotors (or any other parts) to insure everything is square in the car.
Scott
SCOTT....thanks for explaining all that....it sounds like the way to go and then it will be done correct...cool ..thanks
Posted By: mercman1
Re: rear end alignment - 10/04/10 03:16 AM
Don't bother with all that welding and drilling your shock plates or what ever that guy was trying to say. unless you are WAY off put shims between the forward leaf spring mount and the body to move the one side back until the axle is square.
well i did as you said.....leveled car...plumbed down from pivot points and rear spring hangers ...snapped a center line and used a framing square to draw lines for rear end reference and figured out my rear is off 1 7/16....so if i slide it over to the right 3/4 of an inch she will be square.....also slotted spring bolt hole and moved rear back 3/8 of an inch....now all i have to do is figure out my pinion angle....right now the trans is minus 5 and the pinion is at 0 degrees......maybe i should minus the pinion to -2 degrees to get me right......what do you think???.....i am cutting and rewelding new saddles on