Re: rear end alignment
[Re: GEORGE68HEMIRR]
#820363
10/03/10 04:06 PM
10/03/10 04:06 PM
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Joined: Dec 2003
Posts: 2,586 Illinois, Indiana, Louisiana
ProStDodge
master
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master
Joined: Dec 2003
Posts: 2,586
Illinois, Indiana, Louisiana
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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
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Re: rear end alignment
[Re: Dave_J]
#820369
10/04/10 12:56 PM
10/04/10 12:56 PM
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Joined: Jan 2004
Posts: 27,347 Today? Who Knows?
1_WILD_RT
Management Trainee
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Management Trainee
Joined: Jan 2004
Posts: 27,347
Today? Who Knows?
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Quote:
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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.
I see, just Micky Mouse it and all should be OK. Do it how you want.
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EDIT: But when he moved the springs into the frame rails, there is no longer a front hanger. The holes replaced the hangers. So he must get the holes in the right place.
If its off just a bit, elongate the holes to where it needs to be and weld up the bad side.
You need this to be right with no slop. If you have some slop they will move no matter how tight you get the bolts. Do you want your rear springs moving around when you got both front wheels off the ground???
The way I have handled critical alignment holes that were mispositioned or elongated is to intentionally elongate the holes, add oversize washers to the bolts, position everything precisely then tack the washers in place....
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