school me on add a leafs for load not lift

[Stomis]

Well with the blazer tank in the truck with a full tank and the metal bed on I've got upwards of 300 lbs more over my rear than ever before. Which wouldnt be a problem if I hadnt built my 56" springs I put in for a super light rear...

So now with a full tank my springs are almost full flat... The question is where can I get add-a-leafs that arent for lift but rather just provide more carrying capacity?

Also does spring rate go by what they can hold in the LB's or am I thinking about it wrong? Since I'm expecting to carry 400 more pounds than before I wouldnt need to split that number and therefor add a 200lb spring rate AAL in each pack would I?

When I put my 52's up front I'll have an entire 4" lift 48in long pack I can use for springs but if I could calculate the right amount of spring rate I need to add and put the proper leaf in each pack I'd rather do that.

O yeah btw I dont want to make my spring stiff as a board, they flex really well....

 

[Hogback Fabrication]

Leaf spring rates aren't linear, they will always have a higher spring rate in compression than they do in droop (and hence, leaf spring suspensions have more downtravel than uptravel).

Adding a leaf or two will increase the spring rate which will give you the ride height you want.

Spring rates are in lbs/in, or how many lbs it take to make that leaf sag 1". So, yes, if your springs are 200 lbs/in and you add 400 lbs. in the rear of the truck it will make the rear sag 1" (because there are two springs sharing the load).


Here's a calculator to give you a guess on leaf spring rates

 

[Stomis]

Alright so say the back of my truck sags 2 inches when I load it up. And I put a 2in AAL in there. Isnt that gonna hike my ass end way up when the back isnt loaded?

Thats exactly what I dont want....I wanna increase spring rate w/o lift. I think stock leafs added in would be a better option no?

 

[Blue85]

Then only option I know of that keeps the rig flat regardless of load is air springs.

The higher the spring rate, the less the height changes with a given load, but you are giving up ride quality and flex as you increase it. A regular add-a-leaf is exactly that - increased spring rate. You can get "helper" springs that only take load once the rear sags. This saves the ride quality when unloaded, but can eliminate your droop off road (and of course the rear has to sag). There might be one that lets you crank bolts down to add more spring when you need it.

EDIT: Oh yeah, the best option would probably be adjustable coilovers if you ever wanted to take things that far.