Leaf spring relocation

[69'Net]

I know this is the b body site, but I'm doing a spring relocation on my 69 dart swinger. I have everything mocked up and ready weld. I'm just adjusting for square with a plumb bob and tape on the shop floor. I'm 2/16" out of square. I've spent hours adjusting and just can't seem to get any better. Am I being **** and making Swiss watches here or should I just start laying bead? If anyone knows more than me (not hard) feel free to chime in. Thanks in advance!

 

[gkent]

What's out of square ?

Unibody construction wasn't perfectly accurate so here's the setup in order of importance:
1) rear spring eye mount holes are in line with each other and are equidistant from the front "axle centerline". You can use the front crossmember as the front reference point for this. Use a long rod through the spring mounting holes.
2) you want the spring eye mount holes at the same height side to side.
3) you want the front perches moved in as close to equal on both sides but there is wiggle room here.

When I did mine I didn't use a plumb bob or floor reference points. I only used a digital level and tape measure. I had the car up on a hoist so I was doing everything comfortably standing. The first step was getting the car dead nuts lever front to back and side to side - which ensured the car wasn't twisted. I then took some measurements using the holes in the front crossmember and the rear frame rails to check squareness. If those pieces aren't square to start with then you have to decide what to do about it to compensate. But the end result is you want those first two points I listed to be dead on before you weld anything in place.

 

[69'Net]

What's out of square ?

Unibody construction wasn't perfectly accurate so here's the setup in order of importance:
1) rear spring eye mount holes are in line with each other and are equidistant from the front "axle centerline". You can use the front crossmember as the front reference point for this. Use a long rod through the spring mounting holes.
2) you want the spring eye mount holes at the same height side to side.
3) you want the front perches moved in as close to equal on both sides but there is wiggle room here.

When I did mine I didn't use a plumb bob or floor reference points. I only used a digital level and tape measure. I had the car up on a hoist so I was doing everything comfortably standing. The first step was getting the car dead nuts lever front to back and side to side - which ensured the car wasn't twisted. I then took some measurements using the holes in the front crossmember and the rear frame rails to check squareness. If those pieces aren't square to start with then you have to decide what to do about it to compensate. But the end result is you want those first two points I listed to be dead on before you weld anything in place.

Thanks for the response! Unfortunately dont have a lift so im stuck with using a bob. The measurement that was off was the cross measurement from front to back. My measurement from rear spring eye to front perch is dead on. I cant run a rod through the rear spring eyes because the trunk on a 69 dart has an indention for the spare tire that's in the way. So what I did was cut the mounting ears off the new rear spring bracket and then bolted the old bracket in place and lined them up properly using a short dowel. They were off. Now my measurements are correct front to back and cross. I'm wondering if I should tack it all in place and put the springs on and measure from the front cross member to the center shackle bolt to make 100% sure they're centered?

 

[gkent]

If everything is square, don’t use the springs as reference points. What if they’re out of whack, you’d be altering the car to fit a defective part! Let me tell you this, if I’d used your method my rear end would be royaly fucked up because the left front spring mount was welded in in the wrong position from the factory!

 

[69'Net]

If everything is square, don’t use the springs as reference points. What if they’re out of whack, you’d be altering the car to fit a defective part! Let me tell you this, if I’d used your method my rear end would be royaly fucked up because the left front spring mount was welded in in the wrong position from the factory!

Wouldnt I know if theyre defective if I measure them from a fixed area on the car like the cross member? Unless the cross member isn't straight? A lot of "what ifs" when you start thinking about it.

 

[gkent]

I'd count on the front and rear crossmembers and frame rails being pretty close to where they should be. But those front spring hanger mounts are separate pieces that were welded in. At some point you have to say "that's it". If you're confident things are square and level, weld 'er up !

 

[topside]

Main thing is to get the rear axle square with the front spindles so the car will go straight.
The body dimensions are often "off" from the factory - I've seen as much as 1/4".

 

[69'Net]

I'd count on the front and rear crossmembers and frame rails being pretty close to where they should be. But those front spring hanger mounts are separate pieces that were welded in. At some point you have to say "that's it". If you're confident things are square and level,

Main thing is to get the rear axle square with the front spindles so the car will go straight.
The body dimensions are often "off" from the factory - I've seen as much as 1/4".

How do you square the off the spindle? Align the steering first off the cross member?

 

[gkent]

How do you square the off the spindle? Align the steering first off the cross member?

Forget that, "topside" is living in fantasyland. For the average guy in his garage or driveway you measure off of crossmembers, frame locator holes, etc.. Whatever would be consistent on both sides. And to your comment, if you were going to align the steering with the crossmember then why bother with the steering at all ?!?!?

 

[topside]

Not literally with the spindles, that was inarticulate of me; my point was that all 4 wheels need to be square. That can be determined by locating and confirming using a number of spots, rather than assuming anything. That's how we've set up any number of race cars, whether drag racing, vintage TransAm, or pavement or dirt Sprint Cars.