Lowering block doesn't lowering

[antipop]

I explain my problem

I have Hotchkis leaf springs 2" lowering on a 1970 firebird

The driver side is a little bit more 1" higher than the passenger side with the new leaf springs, I think it's a big "chevy lean"

I drove 500 miles and the leaf springs always have the same 1" height difference

The front of the car was a little lower on the passenger side so I add a shim on it and now the front is ok,
but no difference at the rear

So I tried switched the leaf springs and it s the same (with 100 more miles on them)

Now I have installed lowering block on the driver side (1") and the car lowered ... 1/2", so I tried 1.5" block and the car lowering almost 3/4"

Driver side is always almost 1/2" higher with a 1.5" lowering block on it !

I don t understand, I tried switched leaf again, no difference, I checked the schackles torque and schackles length and there is no problem,

I checked everything and I notice that the leaf springs have the same arch when I don t add lowering block but with a block the driver side leaf is always more arched after (so the block doesn t lower the car enough)

Without block both leaf springs look "flat" (not really flat but with a very small arch)
With a block driver leaf looks a little bit arched and passenger side stays "flat"

I asked Hotchkis and they have no idea of what is the problem, they said that with a 1" block the chevy lean must be corrected by 1"

They ask me to switch leaf springs again, to check the arch of the leaf springs disassembled from the car, .... but everything is right and they don t understand the problem

The frame is straight, the car is ok to drive (with or without lowering block)

But the lowering block on the driver side doesn t lower the car as much as it should and the leaf spring on the driver looks more arched when I add lowering block (so the car doesn t lower enough)

Does anybody know what is the problem ?

[streetk14]

It seems to me that using a lowering block on one side isn’t a great option, and might be why it isn’t quite lowering the car as it should. Could be wrong, but that’s my thought.

As far as the height differences, I had a similar problem. My left side was higher front and rear. After doing a full front suspension build with coilovers and setting the ride height where I wanted it, my rear ride heights became much closer. I think I went from close to 3/4” difference side to side on the rear to maybe 1/4”.

The thing to keep in mind is these cars are old and the build tolerances weren’t great even when new.

[dontlifttoshift]

When you install one lowering block you put more corner weight on the opposite side. If you put more weight on the opposite side you then have less corner weight on the side with the lowering block.

Are you measuring at the wheel lips? Try measuring at the rocker.

[antipop]

When you install one lowering block you put more corner weight on the opposite side. If you put more weight on the opposite side you then have less corner weight on the side with the lowering block.

Are you measuring at the wheel lips? Try measuring at the rocker.

I measured at wheel lip and rocker

If I put a lowering block on one side I put more weight on the side with the lowering block I think, no ?

The more you lift one side (with a jack for example) the more the opposite side compress,
so the more you lower one side, the more the opposite side raise

[dontlifttoshift]

That is wrong. Side with the lowering block is compressing the spring less, side without the lowering block is compressing the spring more. If spring rate is 150 pounds per inch and spring is compressed 3" on lowering block side and 4" on not lowering block side then lowering block side will have approximately 450 pounds on it and not lowering block side will have 600 pounds on it.

I only trust rocker measurements and even they are an approximation. Wheel lips can easily be in the wrong spot......even on all original sheet metal.

[antipop]

That is wrong. Side with the lowering block is compressing the spring less, side without the lowering block is compressing the spring more. If spring rate is 150 pounds per inch and spring is compressed 3" on lowering block side and 4" on not lowering block side then lowering block side will have approximately 450 pounds on it and not lowering block side will have 600 pounds on it.

I only trust rocker measurements and even they are an approximation. Wheel lips can easily be in the wrong spot......even on all original sheet metal.


It makes sense with tge difference in the arch of the leaf springs (even if I don't really undersrand the physics of it)

What can I do to correct the lean on the passenger side and lowering the driver side ?
And to keep the same pressure on each leaf ?

[dontlifttoshift]

There was zero change when swapping the leaf springs so it isn't the leaf springs.

For giggles I would disconnect the shocks, give it a bounce or three and see if it changes.

After that, take really good measurements on the levelest surface you can find. Put a floor jack under the passenger front and jack it up a bit.....just enough to see daylight under the tire. Now what's it measure? All four corners, before and after.

[68Formula]

For giggles I would disconnect the shocks, give it a bounce or three and see if it changes.

Weird, I tried to reply this yesterday, and it didn't show up. Anyway I was thinking the same thing. Take the shocks out of the equation and see how it sits.

[antipop]

I tried disconnect the schock and bounce it, no difference

I begin to understand the problem with lowering block and pressure applied on each leaf

What do you think of "adjustable leaf spring pocket" like this

https://innovativeracecraftfl.com/shop/cjrc-leaf-spring-buckets-70-81-camaro/

Can I use them to adjust the height of the car if I don t use the same hole in each leaf pocket ? Bad or good idea ?

Or another idea :
The body is twisted a bit I think (cause of my problem) so

Is it possible to add shims between frame and body on passenger side to raise the front passenger of the body (and so lowering rear driver side) ? Bad or good idea ?

[68Formula]

You should try to find the root cause, not work around it. A 1" difference is not normal.

Have your subframe measured. And verify your body bushings are in good condition.

[dontlifttoshift]

Did you do this? Wheel lip and rocker measurements.



After that, take really good measurements on the levelest surface you can find. Put a floor jack under the passenger front and jack it up a bit.....just enough to see daylight under the tire. Now what's it measure? All four corners, before and after.

[antipop]

Did you do this? Wheel lip and rocker measurements.


All the bushings are new in the car (and body bushing are aluminium)

If I raise the front passenger side a little (closest to the wheel that I can with a jack):
it s a little bit better in the rear (but always with the lowering block)
and the front driver side raise as much as the passenger side