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Discussion Starter #1
Hello all! Finally jumped into the fray here because I finally found a question that searching this site couldn't answer. It would be easy enough to just ask my question here and be done, but I didn't want to be the guy to come in asking the same question over and over.

So instead of asking how much lift I will get with it on perch 0/1 etc, I was wondering if a formula exists that calculates spring/shock data to ride height AND/OR wheel travel with regard to over all shock length? I understand the basic physics behind the problem, but I can't find enough data to make my own formula work. The best I could do without the factory spring length was factor a linear slope for the four perch settings on the 5100s, then graph for the spring rate and corner weight.

Backstory: Currently I am running a simple 5100s on notch 4 with factory springs. I recently added a winch on a custom plate and I want to get back up to 2.5 - 3" front lift. I bought a pair of 600lb 15.5" front springs off a guy on a local toyota fb page. They are made by "Headstrong Offroad" for Tacomas on bilstein 5100s. I am told they closely match the OME 885. I got them in near new condition for a really great price, so I won't be too sad if they don't work out.

Thanks for any help!

Pic of partially finished winch build (credit to Jimmy Speranza forthe idea and walkthrough).

1122111
 

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Let me preface this post by saying I hate spring design. I have never heard of such a specific formula but I think its more complicated than you think. The motion ratio with the LCA at various angles creates its own small challenge. And shocks have internal nitrogen charge that pushes down, around 100 lbs of force. Using some of the below references might help. You could pull the factory springs and measure their free length. And you know their compressed length.

Maybe this will help:
Factory front spring rate is 616-633 lbs/inch The Factory OE Spring Rate?

If you want to do a simple comparison on your setup, the rough math is, your new springs are approximately the same rate as the OE springs (esp. considering the OE may be a little weak after a few years). So then the comparison becomes easier between the two once you know the difference in free heights.
 

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Discussion Starter #3
Let me preface this post by saying I hate spring design. I have never heard of such a specific formula but I think its more complicated than you think. The motion ratio with the LCA at various angles creates its own small challenge. And shocks have internal nitrogen charge that pushes down, around 100 lbs of force. Using some of the below references might help. You could pull the factory springs and measure their free length. And you know their compressed length.

Maybe this will help:
Factory front spring rate is 616-633 lbs/inch The Factory OE Spring Rate?

If you want to do a simple comparison on your setup, the rough math is, your new springs are approximately the same rate as the OE springs (esp. considering the OE may be a little weak after a few years). So then the comparison becomes easier between the two once you know the difference in free heights.
Interesting... I read in that thread that the OEM rate was ~500lb/inch. Now I'm super confused!

Off to read more.
 

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Discussion Starter #4
OK, more reading done. I see where you are getting the 616-633lb/inch figures now. I'm curious where the 500lb figure comes from.

I think I will probably just swap the springs out and get some basic tapemeasure data while I'm at it. I have been concerned that they were going to be too stiff!
 

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Don't rely solely on spring rates for ride comfort:

My KINGS with 550lbers ride harsher than my S.A.W.'s did which had 700lbers.
The absorber part of the coilover that controls the compression and rebound plays a part in ride comfort as well,.
 
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