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Hey everyone, I just ordered the Nisstec Gone MOAB extended coil over kit and I had a quick question. I ordered the 600 lb springs because the Nisstec guy told me they would be best for what I have, but I have read some mixed things on here about that. I have a Pro4x with the following mods:
- Full Hefty aluminum skids
- White Knuckle slider
- Shrock front bumper and radiator skid

I plan to add a winch down the road, but my question is, should I go 650 lb springs? or are the 600's good?

Thank you!

- David
 

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The difference between a 600lb. and 650lb.coil spring is almost negligible.
For example, if your cornerweight is 1300lbs.,
the 600 lb. spring will compress 2.16" to maintain ride height.
With a 650lb. Spring it will compress 2.0".
As a general rule, use the lightest springs that will maintain your desired ride height.
Just to add. When I started my build 10 years ago, I had no idea what the stock spring rate was on the truck.
I had to at least get an approximate of what it was to design my suspension.
Anybody have an idea how I did it?
 

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The 600 will probably be fine, I've seen most with a similar setup use a 650 but they also typically have steel skids so the 600 might be the ticket.


Just to add. When I started my build 10 years ago, I had no idea what the stock spring rate was on the truck.
I had to at least get an approximate of what it was to design my suspension.
Anybody have an idea how I did it?
Ratio of corner weight to sag? Then compare with the free length of spring?
 

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The 600 will probably be fine, I've seen most with a similar setup use a 650 but they also typically have steel skids so the 600 might be the ticket.




Ratio of corner weight to sag? Then compare with the free length of spring?
Can you be more specific?
 

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The difference between a 600lb. and 650lb.coil spring is almost negligible.
For example, if your cornerweight is 1300lbs.,
the 600 lb. spring will compress 2.16" to maintain ride height.
With a 650lb. Spring it will compress 2.0".
As a general rule, use the lightest springs that will maintain your desired ride height.
Just to add. When I started my build 10 years ago, I had no idea what the stock spring rate was on the truck.
I had to at least get an approximate of what it was to design my suspension.
Anybody have an idea how I did it?
This doesn't take into account preload. If you preload the 600lb spring more it will not sag as much at ride height, therefore making it compress the same amount as the 650lb spring with less preload at ride height. However the preload, will not change the rate that the spring compresses while on the trail. The stiffer spring would be more useful if you find that you end up blowing through the travel because of the forces and weight of the vehicle while in motion or your driving style.
 

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This doesn't take into account preload. If you preload the 600lb spring more it will not sag as much at ride height, therefore making it compress the same amount as the 650lb spring with less preload at ride height. However the preload, will not change the rate that the spring compresses while on the trail. The stiffer spring would be more useful if you find that you end up blowing through the travel because of the forces and weight of the vehicle while in motion or your driving.

With the same amount of preload, the heavier spring will ride about 5/32 of an inch higher. Like I said, negligible.
If your ride height is correct and you are blowing through your travel, it is not your springs.
It is because your shocks are not valved correctly.
 

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This doesn't take into account preload. If you preload the 600lb spring more it will not sag as much at ride height, therefore making it compress the same amount as the 650lb spring with less preload at ride height. However the preload, will not change the rate that the spring compresses while on the trail. The stiffer spring would be more useful if you find that you end up blowing through the travel because of the forces and weight of the vehicle while in motion or your driving.

With the same amount of preload, the heavier spring will ride about 5/32 of an inch higher. Like I said, negligible.
If your ride height is correct and you are blowing through your travel, it is not your springs.
It is because your shocks are not valved correctly.
We are both agreeing to concept that either spring would probably work for the OP. Because they are getting coilovers, they can play with preload. And often the softer spring for can be better with a little more preload then a heavier spring with less preload. To keep a smoother ride at slow to moderate speeds. Higher velocity, can often require a heavier spring.Compression damping only controls the speed that the shock compresses not the load capacity, that is the springs job. If you are moving through your travel to quickly because of the speed you are hitting impacts at, then increasing compression can help. If you are bottoming out because of the load at normal speeds then the spring is to soft. This is how Oldman EMU suspension got their reputation. The tend to use more preload then most fixed length setups so that you can have nice ride quality and ride height with some weight on board.
 

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Preload just determines ride height. You mentioned that increasing or decreasing preload has no affect on spring rate. That is correct.
What is the function of a shock absorber? It controls the movement of the springs.
What you are suggesting as a way to keep from bottoming out is something you do when you can not properly valve your shocks.
I mentioned this before. Friends in my group have their vehicles shock tuned at the King test track by their specialist.
This vehicle shown had no less than 11 valving changes in one session. One spring change. Went to a softer spring.
Regular shocks are velocity sensitive. I agree with you on that. Do you know what a by-pass shock is? Do you know what the difference is?
They are position sensitive.
In other words, you can change increase or decrease the sensitivity where ever you want through out the stroke. You can have as many a 6 by-pass valves.
You can have the compression so stiff right before it bottoms out , it functions as a bump stop.
As far as OME, they probably make an ok product for tooling around the "Outback".
Not for desert racing or serious rock crawling.
 

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