Pros / cons of longer springs in coilover?

I've got ICON's 2.5 coilovers w/ remote reservoirs up front. These currently have the original 600lb, 13" spring. I have the coilovers set w/ a bit of preload to give me the desired 2" lift.

I'm considering swapping in 600lb, 14" (1" longer than the original) springs in order to decrease the amount of preload, while maintaining the same lift height. My thinking is that this will give me more suspension travel, and potentially a softer/nicer ride. Am I correct in these assumptions?

Are there any downsides to doing this swap that I may be missing?

 

The length of the spring is irrelevant, a 600lb spring is the same regardless of length. The LB rating of a spring is called the spring rate, the spring rate of a 13" 600 spring is the same as 26" 600lb spring.

Next, If your CO came with a 13" spring that is all the length needed for the travel your CO is capable of. Changing to a longer spring will not make your CO have any more travel.

If you want your spring to hold the truck up better without pre load the correct move is to get springs +50lbs so in your case a 650. A 14" 650 may fit if you cant find a 13" 650 but just know the extra length is doing nothing for you.

 

^^ What he said and I'd believe you would have more chance of "coil binding" the spring under compression.

 

Thanks, @Evenflow and @Bloodhound. Glad I posted this. Will rethink things.

 

Not more shock travel, but less preload means easier/softer uptravel at the end.

Nothing? Yes it helps, no need to preload so much. You maintain softer ride with 600lb springs instead of 650lb.

Preload causes binding, 14" springs have a coil more but the locking ring is higher. About the same situation.

I'd take the longer springs rather than stiffer (650lb) ones.

 

Hmm... @FinnJ - that's kind of what I had in mind. When you say that less preload will result in "softer uptravel at the end", when would that be noticeable? Say I'm driving in the city and hit a pothole or other road imperfection, the shock & spring will compress (and I think this is where most of the discomfort is felt, right?), and then decompress "softer"? I guess I'm not sure how that would affect the feel of the ride...

I would imagine that the longer spring (but with the same spring rate) would compress softer, and that would be on the down-travel (resulting in a more comfortable ride when hitting bumps), not up-travel. Is that not so?

 

^ I think quite similar with you. Here is a good reading: https://www.eatondetroitspring.com/cutting-coil-springs-calculations/

And this is for bikes, but suits well for cars/trucks too: http://www.sportrider.com/technicalities-spring-rate-and-preload

 

Holy fawk ! What are you guys talking about, spring rate is spring rate is spring rate, a 1' or 2' longer spring of the same rate is not going to accomplish a fucking thing for this guy. It will still require the exact same amount of preload ! Go ahead and call any professional and ask that question, @jberry813 @Downsouth Motorsports back me up here guys.

 

No you are dead wrong, that longer 600lb spring is still going to require the exact same amount of preload as the shorted spring.

 

Should we argue? Please think twice. Think if you have 2" longer springs, you don't have to preload them at all (if you are able to get the collar on the thread), they will raise the suspension even more than where it was, WITHOUT preload.

 

You are confusing load rating with spring rate.

 

you guys are f-n mental midgets and should be banned from giving anyone advice on TW. I'm only going to say it one more time - a longer spring with the same 600lb rating is not going to hold his truck up any better, period end of story. It is the same f-n spring, holds the same amount of weight...what part of science is so confusing ? He will have to turn that collar the exact same amount of turns with a longer spring of the same 600lb rating.

eventually other folks that actually know their head from their ass are going to chime in here and you are going to feel like complete twats for arguing this point.

 

Raises hand, you are correct on this "first grade", very basic suspension concept.

 

I have 650#/13" springs set at 2" on my Icon ET's for 3" of lift. Rides firm, but smooth.

I'm installing a Pelfreybilt HWM and a Smittybilt 10K winch. (100 plus pounds)

I'm switching out the springs for 700#/14" springs to be set at 1 1/8 inches. I'm also going to take out the diff drop.

I expect the same ride, but with more clearance.

Don't over think it.

 

I agree.

I don't agree.

Calm down please. What if you install coils at rear axle, let's say first springs are 15" long 600lbs, and second springs are 20" long 600lbs. Which ones keeps the rear suspension higher? 600lbs spring means 600lbs/inch, it will compress 1" if there is 600lbs weight on it, 2" if 1200lbs (if linear spring rate). Right?

If the spring is taller, the final height is taller if the spring rate is the same. Not so difficult thing.

 

This is where you are confused.
In your rear scenario you are dealing with a fixed distance between spring seats and of course in that case ride height would increase.
This thread is dealing with an adjustable preload, or an adjustable distance between the seats. With the same given spring rate and ride height, the longer spring will take the same amount of preload. The only difference would be the total length of the preloaded coil, it would be longer.

Tell us what you think would happen in your rear scenario if the distance between the spring seats was increased the same 5" as the longer (20" vs 15") coil.

 

Yes, guys, you are right. I had to draw first before I understood what I am thinking, and yes, this is how it goes. Somehow I thought longer springs would push the suspension out more, and yes, it does if the adjusting collar is at the same point, but then you´d have a huge amount of preload with that longer spring. So the preload is what matters, or lack of it.

Evenflow, thanks, I´m wiser now.

 

This is an old thread, but I found the information in it interesting, and I also found something the other day that I am curious about. Before anyone gets triggered, I acknowledge that I am a mental midget in virtually every category of life.

It sounds like OP wanted to know if a relatively longer spring would produce more lift due to its length, which would allow him to reduce preload. Now, consider the following OME coil specs:

Coil specifications:

• OME 887: 400mm in height 590 pound spring rate
• OME 888: 405 mm in height 590 pound spring rate

The 888 is 5mm longer than the 887, but has the same spring rate. Yet, a lift guide from Headstrong states that the 888 coil provides an additional 0.5" of lift across the board:


https://www.headstrongoffroad.com/uploads/1/1/8/4/11846658/lift_guide_sep_4_2018.pdf

Maybe I am overlooking something, but it looks like the additional 5mm of length in the 888 coil translates to an additional 0.5 inches of lift. Is this additional 0.5 inches of lift lost when some degree of preload is incorporated?

 

The problem I think your overlooking is that the ome coils are not supposed to be preloaded.

 

This goes back to what Dirty Pool said. Assuming an identical spring rate, both springs are compressed the same amount under the same load (static vehicle weight). The longer spring is still longer under identical loads. In the case of the 887 vs 888, the 888 should still be roughly 5 mm longer even under the weight of the truck. That 5 mm "lift" is multiplied by ~7/4 due to the shock mounting location on the control arm relative to the total arm length, yielding close to 0.5 in.

Changing the shock perches to "preload" the spring really only changes the length of the shock relative to the spring (while under static load).