I have the DeSoto on the road now. Everyhing is cool with the exception of the rear leaf springs.

I used new Summit Racing lowering springs for a 74 Cuda. 130in/lbs 57" long

At first they were fine but as time goes by ( 1 week) they sink lower and lower....too low

Im afraid if I buy regular height springs the same thing will happen

Any suggestions?

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Add a couple of extra leaves into the "stack" to get your preferred height & stiffness.

These days, I do this job right under the vehicle by jacking it up, supporting the chassis on jack stands, removing the lower shock mount & U-bolts and then use "smart thinking", big c-clamps, plumber's tape, bailing wire, etc. to support, then carefully remove the centre pin/bolt, spread-open the stack and slip-in the needed extra leaves.

I go as far as using 1/2 leaf sections or turning leaves up-side-down, in order to gain stiffness, while setting ride height.
Another "trick' is to use a long leaf with lots of arch on the bottom of the stack...(like a "helper spring) and then cut it shorter (or heat it with a torch) to "fine-tune" the ride height.
DD

130 springs sound pretty light duty for a big old DeSoto.

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Official Cookie and Mater Tormentor.

They should stabilize after a few weeks, unless they are really cheap junk. I would wait for that to happen before you buy anything else. Then you can make changes as Doc describes. How much wt on the rear of the car? Regular ht springs will settle in about 2-3" higher than the lowering springs, I would guess.

Lou

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Home of Slant6-powered fun machines since 1988

Will a longer shackle work?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I think the springs are too light.....

I may try a set of used stockers for a baseline then play addaleef.

I have no shackles ,,,I used sliders. I will try spacing the sliders to add height.....a simple piece of 2x4 between slider and mount will tell me lots.

I have no idea of rear car weight....the car is funny in that it has a long wheelbase (126") ....the front face of the motor is in line with the spindle centres ( a foot astern of most cars) so the weight on the front wheels makes it feel like an early A when there is no power steering. I have considered going manual steering....

The stock car weight is 3750.

I think the springs may be really cheap junk.....

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Yeah....Im the one who destroyed this rare, vintage automobile.....