rear end spring perch location ?

[Butch67]

Hi,
I have mini-tubbed and moved the springs in under the frame on my 71.
It has super sport springs on it.
The question is, on the spring perch there is 3 holes drilled in them.
If I was to move the perch backwards so that the front hole was on the centering bolt for the springs, what would this do to the springs under driving conditions?
I am trying to center the wheel a little more in the wheel well.
I don't have a driveshaft yet as I am going from auto to 4 speed.
I am not sure if I explained this very well, but any help would be great.
Thanks,

 

[mderoy340]

I moved mine back 3/4" on my 67 dart. The rear shock stud also moves back so pay attention to fuel tank to shock clearance. Mock it all up and tack the spring perches on with the correct pinion angle.
I had a 1/4" difference axle to torsion bar measurement before I changed anything.

 

[Butch67]

I have a fuel cell mounted in the trunk, so that won't be an issue.
It's the location of the perches on the springs, and the effect it will have on the springs themselves under driving conditions.
I don't want to put any damaging stress on the springs or poor driving conditions.
I don't need the extra space that bad to affect the rest of the handling of the car.
Thanks.

 

[Johnny Mac]

I really see no difference by the mere inch of adjustment. I'd suggest mocking it up on the center hole, putting your tires on it, and seeing if you'd ever run into the front of the wheel opening if you had a slightly larger tire on it. Thats really the only reason i can even think yours have three positions. Mine didn't. But that 1/2 inch may help someone trying to squeeze 31's under there center the tire enough to clear.

 

[mderoy340]

The replacement perches from Mopar have the 3 holes. OEM only 1 in the center. Moving 3/4 to 1 inch is not going to change the spring. The pinion angle may change slightly which is why I would mock it up before you do a final weld job.
I moved mine back so I could run a 29" tire on the street with a 3.91 gear and not wind the crap out it all the time. When I go to the track the 27 slicks go on the car and it's a totally different ride.

 

[Logan]

I'm not quite following what you want to do but would only caution that if the spring moves back, the angle of the rear shackles may become too severe requiring a similar repositioning of the rear shackle mount on the body.