ATT suspension experts - Lowering and stiffening leaf springs - Car: AE71 wagon

[JoJo]

I have just got a AE71 Corolla wagon. I have just converted to a 4AGTE. I have modified many cars in my time, but never one with leaf springs before, and have never really come across this problem.

The car will be used as a daily, tyre transporter, carry dogs, WILL NEED TO TOW A BOAT (4-500kg approx), light 'sprited' driving on occasions (but not the cars purpose).

I dont really care too much for comfort, but more for functionality, the right 'look' (low) and general safety.

So, after knowing stuff all about leaf springs, over the last week I have been reading about about how to lower them, and peoples feedback/responses.

I have read alot, so just keeping this simple.

Seems to be 3 options that I could find:

Lowering blocks - Does the job, but can be 'unsafe', not the best for handling,

Flipping leafs - Can get it really low, but the handling is dangerous,

Reset and adding leaves - This is obviously the "right" way to do it in terms of safety. No doubt. But I have read many responses where people say the rear still feels "bouncy" and pretty shit. But that old saying, "You can't polish a turd, it's still gonna be a turd".

So before I go ahead and get that done, I was thinking if it can be done another way........ I can understand you shouldn't flip them, as the spring is working at oppisite forces with itself. I have an idea tho, but my question is IF IT IS DANGEROUS TO HAVE THE SPRING PERMANENTLY COMPRESSED?

Follow me here -

So I read 'Javal' saying to take the bottom/shortest/stiffest leaf and put it on top of the spring pack. Said it would make it lower and stiffer..
So I did it:

BEFORE:




AFTER:




BEFORE:



^^^ AFTER:

Ok, now I am learning



So, from looking at the side on shots, you can see its slightly lower afterwards, and that the main pack of springs is now sitting flatter, and the spring is now under pre-load.
From looking at the behaviour of the spring pack and how they flatten out, my idea is, to put that short/stiff spring back onto the bottom (load bearing), and then just add a longer thick/stiff leaf to the top, about the size simular to the length of one of the other leafs attacted to the main one......
It would really flatten out the pack ie; lower, (Lowered)
It would be stiff, being under a fair bit of pre-load (Stiff)
And not 1 spring has been flipped (safety)


I will be using Bilstien short stroke shocks....

Questions:

Am I correct in my theory?

Is it dangerous to have the spring under such pre-load?

Handling effects?




Thanks

[George]

Adding reversed leaf on top is the way to go, you did everything right. Though you may experiment on with longer pieces. Rear now should feel less bouncy and stiffer. Handling-wise, there should be overall feel improvement with maybe slightest understeer tendency

[JoJo]

I got a relpy from a friend, a experienced rally driver who raced older Toyotas.
He was saying that if I get a longer leaf on top, it puts too much stress on the main leaf at the points where the new leaf ends, and that the springs could possibly snap at those points. Resulting is a serious car accident......

I am also thinking another way, to see if I can use actual AE86 rear coilovers, replacing the shock, and stripping the leafs back to just the main one (for mounting/locating) and the short/stiff one for load bearing..... The shock mount points will need to be strenghting a bit, but it should work in theory....