New Leaf Springs Are Sagging

You take the block out and the sag will still be there. It's still the same point of contact whether on the block or the axle.

 

Except your point B is wrong. The point where the leaf spring meets the mounting location is the same point, whether it be the top of the block or the top of the leaf spring perch.

Additional space (made by the block) between the actual axle and the leaf spring will cause other problems, yes, we can all agree on that. But blocks are NOT the cause of the sag in the leaf springs.

 

1000% agree

 

Can't argue with that. Add a 4" block nothing about the geometry changes? Perfect.

 

I'm no suspension geometry expert, but it seems like the springs don't have enough lifting force to actually lift the rear end. So the spring main eye stays at the same height, but the center of the spring is then pushed up a couple inches. Something like the Dakars would have enough lifting force to push the main eye up.

 

The 4" block does not change anything about the geometry in the context of this discussion. "Points A, B, and C" all remain the same, regardless of whether there is a block in there, or not. Point B is actually the bottom of the leaf pack where it meets the mounting location. NOT the axle it's self.

Lift blocks will cause more leverage front and back and side to side. They will not change anything up and down.

Lift blocks will cause more axle wrap
Lift blocks can have premature failure of U-bolts
Lift blocks add ride height without giving you added suspension travel (particularly up travel)
Lift block (dovetailing on the above point) don't give you a better ride quality
Lift blocks can make your truck track wrong
Lift blocks are often cheap and have been known to fail (split)


Lift blocks, how ever, do not cause leaf springs to sag like in this picture (and the context of this discussion). The weight of the load is setting on the point of the leaf spring that contacts the mounting surface, which doesn't change between block or no block.

 

But a and c are not fixed points. They depend on the height of b.

 

The body of the truck is *suspended* by the springs; that is why a 3 inch block provides 3 inches of lift. Along the vertical axis, the geometry remains the same. The vertical distance between the line connecting points A and C and point B is determined by the spring itself. If the spring rate remains constant, then increased weight is required to make the spring flex more. What changes is the distance between the plane of the spring and the rotational axis of the axle. THat is what accounts for the increased propensity for axle wrap.

Edit:
Try this experiment.

1. Measure the distance from the hub to the fender on each side.
   
2. After safely chocking the front wheels, jack the rear end by lifting from the center of the rear axle housing; alternatively, jack each side the same amount by lifting from the axle housing.
3. Repeat step 1; the measurements should be the same, but the distance from the ground to the fender will have increased by the amount you raised the truck.

With respect to your conceptualization of points A, B an C, by lifting the truck from the axle, you accomplish the same thing, in principle, as lifting the spring with a block.

 

It does not matter I have seen that very same thing before .About 6 months after the install

I just went by the pictures I did not see the pictures were the day the springs were installed

Perhaps a mislabeled steel order?

 

I think it's possible that consistent, excessive axle wrap (both during acceleration and deceleration) caused by excessively tall lift blocks could prematurely wear the springs and cause them to frown. This leads back to lift blocks fundamentally causing problems due to axle wrap.

Question for the forum: do lift shackles also cause increased axle wrap? I think I read somewhere that they do, but how could this be true if distance from the spring mount to the rotational axis of the axle remains the same? I think we all probably agree that the best way to achieve rear lift is with more spring rate.

 

For @02RedDoubleCab4x4
On my 2002, I had a leveling kit installed. The back was lifted with extended shackles, using the stock leaf springs. Within 6-12 months, I was replacing my rear springs with a set of Dakars due to my OEM springs looking like yours. So, no, new springs should not do this.

 

Def not normal. I’m backing up the others in the thread. Look for OEM or better if able to. Good luck!

 

Springs cant support weight of vehicle, definitely not right.

 

Maybe you got reg cab springs, and you have a DC. It is quite common for upper leaves to conform to the overload, and that overload is way negative arch (like stock).
If you put a flat (but shorter) overload in there, it will support the upper 3 leaves better

 

OP i'd check a toyota yard for some spares

 

4" Block sucks, get a refund and get better springs.

Ideally you should get a HD leaf spring and add just a 1" block.

 

For all the replies that stayed on the question asked thank you. Many replies were a tangent debate on lift blocks; which was not the question presented. For the record the blocks are 2" not 4". Stock shackles, I do have new shocks to install however the shocks are in one country in my garage and the truck is currently in another country for a couple more months. I am inclined to agree with one reply that stated I may have ordered extra cab springs and my truck is a double cab. I will check into Dakar springs that offer a 2 inch lift over stock height. My concern is that the lift springs may be a stiff/harsh ride. I am in my mid 40s and I am beginning to care more about ride quality.

Good day to you all; enjoy your Tacoma no matter the generation!

 

And the winner is ARCHIVE ; I looked the parts numbers up on sd truck springs website and both springs are for an extra cab .
The more confusing question is why does the reg cab and double cab have the same part number

Extra cab https://www.sdtrucksprings.com/inde...MItY6J9PCp9QIVg8DICh2kYw2_EAQYBSABEgLBJPD_BwE

Reg cab and Double cab https://www.sdtrucksprings.com/index.php?main_page=product_info&products_id=9636

 

That block is also killing them too.

 

It’s not, though