c/o dual rate spring rates

blacktaco666

Well-Known Member
First off, I know this topic has already been discussed, but i couldnt really find a clear answer for my app. I'm putting 10" fox c/o's with resi's on my 01 tacoma ext.cab (glass fenders, tube bumper. nothing super heavy) which already has camburg LT and their 8" c'o. I'm going 10" and dual rates because I noticed the 8" shocks are maxed out at full bump and droop. and they're toast. I also want a smoother ride through the little bumps n stuff so thats why i'm going dual rate. I had no idea what kind of can of worms i had opened by getting these! Pages upon pages about formulas, and some formulas contradicting others... for instance the one where you multiply the rates together, then divide by their sum, and you get a low number... but i read that two springs at the same rate will equal that rate. for instance a 600 on a 600 will always equal 600#, yet the formula i saw will say 300#. That formula also doesnt take into account the length of spring?
Long story short, I got four different recomendations on spring rates:
A friend told me to go 10" and 10" springs like 400 over 500 (he was just guessing but he races, so its an educated guess)
Kartek told me to go with a 16" 600# and a 4" helper
ORW told me to go with maybe a 14" 700# and a 8" 500#... but then he changed his mind and said go with a single 18" 600#
I would like to recycle my 14" 500# springs and maybe use an 8" 400# but i'm afraid it would be too soft?
Any advice or opinions here? It's a Daily Driver and sees the dez on weekends... Anyone with the same setup? thanks
 
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WannaB-class5

Well-Known Member
Wow, it might take pages and pages to clear all that up. I will start with a few things I know. A 600/600 dual rate system will not give you a 600# rate. It will give you 300 lbs. Maybe an explanation of what the spring rate means will help...I am no expert but I will do my best.

A spring with a 600 inch pound rate will collapse 1" if you set 600 pounds on it. Simple right? (These springs are for all useful purposes have a linear spring rate) So if you set 1200 pounds on it, it will compress 2". If you set 300 pounds on it...yep it compresses .5".

OKAY now if you have two 600lb coils, one on top of the other (a dual rate coil-over!) and you set 600 pounds on it what will happen? Well the first spring will compress 1", and guess what, so will the second spring! So how far did they compress? Two inches total.

So if 600 pounds caused the springs to compress 2", then what is the spring rate of this set up? 300 pounds! So the formula you found is correct. Spring rate 1 times spring rate 2 divided by spring rate 1 PLUS spring rate 2. Or in our example 600x600/600+600 which is 360000/1200 which we know is 300!
 
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WannaB-class5

Well-Known Member
Oh and I can give you three options for your specific truck. 1) find someone with your exact set up and ask them (seriously). 2) give us your corner weights and we may be able to help better. 3) stick with the rate you have now if you like it, just make sure you don't have coil bind (which if you didn't have it before, you shouldn't now).

Also, you will need your main rate to be close to what you had before to keep your truck at ride height. And you mention you want it smoother in the little stuff, have you spent any or a lot of time valving your shocks? Is it perfect on the jumps and big stuff but not the small? SOOOOOO many variables.
 

blacktaco666

Well-Known Member
you're right, there are soo many variables!! im going to spend a looot of time tuning my shocks, springs, and weight. i'll keep you posted on here when i get my new shocks in next week.
 
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