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Discussion Starter #1 (Edited)
If everything goes as planned I will replace the mono leaf springs on my '67 coupe.
I have already upgraded the front suspension with "stock" springs, gas shock absorbers, ball joints, control arm bushings and sway bar end bushings.
By saying that the rear end has to be at stock height as well.
I think the car has the correct ride height (without load) after measuring the front and rear ends but in my opinion the rear end is too soft. When loading the car with myself and a passenger the rear end will get much more compressed than the front end.
I have searched for information on this site and as far as I understand the mono leaf springs are too soft - or?
On the other hand - if I go for a pair of multi leaf springs I am afraid the rear end will be too high as far as I can understand from the search results.
Does anyone know what type of leaf springs I should use to achieve a stock ride height but with a little stiffer spring rate?
Maybe I just need new stock mono leaf springs and they will feel good enough since my current leaf springs might be worn out. But can they be worn out without loosing the ride height?
This is the car with the tank full of fuel.
 

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I had good luck in getting 40 year original monos re-arched at a truck spring shop, $1 pound (around $55 total). They had the stock ride height specs, I had them do 1.5 inches over stock. That put the ride height right where I wanted it (with a nice rake) and have not had any issues with it bottoming out when loaded.

 

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My monoleaf springs along with stiffer KYB Gas-A-Just shocks did the trick for me in the rear on my 67. I also put in extended bumper stops for the rear axle onto the frame to keep the axle from ever bottoming out. Got 275/60R15s on the rear.
 

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Your rear height looks good, but your front looks high. Were the A arm frame bolts tightened with the car resting on it's wheels?

"If" the rear springs haven't sagged, they haven't lost rate. The rate for a mono-leaf spring is very soft around 80 to 90 lbs/inch.
High performance three leaf springs for example, have a rate around 175 lbs/in. This would be a Detroit Speed, or Hotchkis leaf spring.
Z/28 multi-leaf springs are in the low 100's around 125.

Re-arching may work, but the design of the rear shackle creates a rising rate due to the angle of the shackle nearing full bump (more angle = stiffer, the spring get's longer as it flattens out). If leaf arch is changed, (beyond stock) the length changes and it may position the shackle in a more vertical position which would make it feel softer. If the leaf is re-arched back to factory spec, it's fine. You need to check the leaf very carefully for cracks before spending money on them.

Most gas shocks add 45lbs of spring rate due to the gas pressure. This generally raises the rear about 1/2".
 

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Discussion Starter #5
Your rear height looks good, but your front looks high. Were the A arm frame bolts tightened with the car resting on it's wheels?
Yes, I tightened them with the wheels on the ground. But I think, after looking at the car in the garage that the front wheel must be in a cavity. I would say that the ride height is about an inch too high in the photo.

"If" the rear springs haven't sagged, they haven't lost rate. The rate for a mono-leaf spring is very soft around 80 to 90 lbs/inch.
High performance three leaf springs for example, have a rate around 175 lbs/in. This would be a Detroit Speed, or Hotchkis leaf spring.
Z/28 multi-leaf springs are in the low 100's around 125.
Re-arching may work, but the design of the rear shackle creates a rising rate due to the angle of the shackle nearing full bump (more angle = stiffer, the spring get's longer as it flattens out). If leaf arch is changed, (beyond stock) the length changes and it may position the shackle in a more vertical position which would make it feel softer. If the leaf is re-arched back to factory spec, it's fine. You need to check the leaf very carefully for cracks before spending money on them.
Most gas shocks add 45lbs of spring rate due to the gas pressure. This generally raises the rear about 1/2".
I dont think my leafs are sagged. After inspecting them I cant find any cracks.
If I would buy an aftermarket spring as for example the 4 or 5 leaf springs from Classic Industries or Rick's Camaro will they raise the rear end?
As far as I understand the leaf springs from Detroit Speed and Hotchkis will lower the rear end. Since my front end should have stock ride height I would like to have stock ride height in rear as well but with a little stiffer spring rate if it is compatible.
After reading a lot of posts here where people have bought 1 1/2" lowering leaf springs and the ride height is still as high as with stock springs, I have been a little afraid of buying something that will not work and I have to ship them back to U.S. for replacement.
Rgds/Mikael
 
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