Lighter truck: more preload, heavier truck: less preload? 650lb vs 700lb coils

So I wanted to see if anyone had any thoughts on this matter, but I have a set of fox 2.5 CO's with 14" 650lb coils on them on my 1st gen.

They've been great, but at this point I've got about 3" of preload on the coils in order to maintain the ride height I want (2.5in+), which is way too much.

What I'm stumped about is that my buddy @Dan8906 has some new ADS 2.5's with the same 14" 650lb coils on them, but only needs like 3/4" of preload to maintain the same height.

My truck weighs 4460lbs with an empty bed. 2600lb of that is on the front axle. His truck weighs 800lb more than mine.

I do have more castor than him with mine being at 4.35 and his at 2.5. Maybe that plays a role?

I've checked the nitrogen charge in the shocks and it's at 200psi where it's supposed to be so that wouldn't be contributing to it.

When I called and talked to Accutune (who I got my shocks from), they said I should go to 700s.

That's likely what I'll do, but I'm hesitant to based on what I've heard from other members about 700's being too heavy for these trucks unless you're like 1000lb heavier than my current weight.

Is there anything I might be overlooking? Anyone with 700's on their truck care to share their experience with them?

 

My guess is that it's due to one of a few factors:

• Spring age
• Spring manufacturer (rating methodology)
• Spring variation (materials)

It'd be interesting to see if you swapped springs (only) with @Dan8906, if you'd see a difference in ride height. That's really the only way to compare apples to apples. I mean, it could be that if you get 700lb springs, you end up with something totally rough horrible to sit it, whereas if you went with new 650lb springs, you'd get exactly what you're looking for.

As a point of reference. My truck is ~5500 loaded (2700 on the front wheels) and I run 650lb springs. Mike @Digiratus is slightly heavier - pushing 6K I think - and he now runs 650's as well (down from 700s).

 

When I went to ADS COs, I also went to 650# coils. I was a little skeptical and was pleasantly surprised the 650s were heavy enough for my rig. An interesting point is, so my truck sits somewhat level, I have about .75" of threads showing on the passenger side and about 1.25" of threads on the driver side.

My old Kings had 700s.

How many miles are on your Fox (Eibach?) coils?

FWIW, my original COs were SAWs with 650# coils. In the long run, those coils were unable to maintain the ride height I wanted. I kept having to add 'preload' to them. This was one of the reasons why I went with 700s on the Kings. In retrospect, I probably would have been fine with 650s on the kings.

 

Is the full weight of your truck on the ground in this pic? Your CV axle angle is much greater than mine.

 

These are things I did think of, but the springs are about a year old at this point. They are eibach 3.0 14". Bought them new from accutune. I measured them when I got them and they were a true 14" length as well. And when I talked to Accutune, they said that springs only really settle about 1/8" max when they "break in"

I wouldn't wanna swap coils with him because that's pretty labor intensive, but maybe rather swap coilovers and see if it maintains that height I'm looking for.

Your front weight is almost the same as mine so it confirms my suspicion that I should in fact be OK on 650 coils.... hmmm....

The difference between sides makes sense for the fact that you have the driver, battery, and gas tank all on one side. I have the same sort of thing on mine in terms of difference of preload.

very few miles on those coils. Less than 10k I would guess. They're about a year old I think.

I'm wondering if I got a bad set of coils or something. Because it does seem that I keep having to add preload.
I've adjusted them I think 2 times now since swapping them from the 600's that the CO's came with.

Yea that's full weight on the ground.
I shoot for about 18.75 length between the top of the top hat to the lower eyelet.

About 1.30 in shy of full extension for these shocks iirc.

I will add limit straps eventually. And I'm not really concerned with CV angles since I have manual hubs so they're only ever spinning on the trail.

 

I suspect you will sit lower than you like if you swap to Dan's COs.

Here's what my passenger side looks like:



Same side, what the UCA angle looks like:



That's 23" from center hub to the bottom of the flare.

 

I think you are going down a rabbit hole by comparing two different trucks with two completely different coilovers. We dont go off looks, we go off specific data like shock lengths, spring travel etc. Every truck is different.

How exactly are you measuring preload?

 

Yea I probably am. but the coilover itself shouldn't have much affect since the coils themselves are what holds up the weight of the truck right?

Totally agree that every truck is different. I'm just trying to wrap my head around why I have so much more preload than others with a lighter weight truck.

I'm measuring from the top of the threads where they start to the top of the upper spring perch.
(note this is an old picture and not representative of the preload I currently have)

You might be right. I also just might be shooting for too high of a ride height.
I'll take a measurement of the fender to hub when I get home to compare

EDIT: I'm 22.5-22.75" from hub center to bottom of flare. So same amount of lift as you I guess

 

Threads showing is not preload, its just threads showing. If you are going to start comparing your setup to someone else's and do it accurately, you would need to scale both vehicles to get corner weights, then gather shock lengths for each coilover to compare. Shock bodies could be different lengths etc. You are not comparing apples to apples. We reference numbers like this on the daily btw Fox/King coilovers. They are not identical

To measure preload on an OEM coilover, you will need to measure the spring when the shock is fully extended. Subtract that number from spring length (14").

Maximum preload= (spring travel) – (shock travel),
Min Preload = (spring free length) – (coilover spring space)

This article may also help with understanding preload and shock setup:
https://accutuneoffroad.com/preload-adjustments-on-oem-fit-coilovers/
https://accutuneoffroad.com/oem-front-coilover-shock-setup/

 

I'm not an expert on suspension........you have about 1300 lbs on each front wheel to be supported.

So a 650 lb/in spring will compress roughly 2 inches to support the truck weight. A 700 lb/in spring will compress roughly 1.8-1.9 inches.

Shocks do nothing to support weight, they only control rebound rate.

I'm doubtful if the 0.2 inch loaded spring length will make much difference in your ride height.

IMHO you are chasing vapor on this path.........

 

I bet there's a difference between the center of the lower shock bolt to the bottom of the spring between coilovers. Same thing from the coilbucket to where the threads start. Apples to Oranges. Measuring how Accutune suggests will answer that.

People get all caught up with threads showing but it's not a huge deal. As long as you're not getting into coil bind you're fine.

 

Thanks for clarifying. When I spoke to your staff on the phone and I explained how much threads were showing, they didn't correct me to say that I was measuring it wrong so I just assumed that I was right.

When I get home I'll take some measurements of my coilovers to measure the amount of preload I currently have to compare against the max recommended.

As far as terminology, how do I know what the spring travel is? I assume it's not 14" because the spring obviously isn't going to travel 14" from free length to full compression.
And what is "coilover spring space"?

Less than 1300lb. Part of that is unsprung weight too.

You're right that it won't do much for ride height. But from my understanding if I'm close to experiencing coil bind on my current 650's, going to a 700 might solve that issue by allowing for less preload, right?

Yea I'm gonna start to do some more measuring according to their articles so that I can measure actual preload and not the threads I was measuring before.

The only reason I was concerned is that when I talked to them on the phone, they said I'm very close to having enough preload to start to experience coil bind. So I just want to make sure that I'm not at that point or too close to it.

 

It can get confusing definitely.

Spring travel is pretty straight forward, just the total amount the spring can travel/compress before reaching block height/coil bind. Eibach has a chart that lists a lot of their spring travel numbers so 3.0 x 14" x 650lb spring has 7.39" of spring travel and will block will be 6.61" tall. Spring space is just the space in btw each coil.

Correct, if you are close to coil bind, you need to go up in spring rate. This will require less preload to get that same shock length and eliminate potential coil bind.

 

Gotcha. So the max preload for my springs on my shock is 1.90in based on the extended and collapsed lengths you have listed on your site. I'll check where I'm at.

And for spring space would I be measuring the spring space between the physical edge of the coils, or from center to center of each one? And is that measured with the spring at it's free unloaded length?

I appreciate you guys being active on the forums. It's a huge help. Awesome customer service.

 

Thats correct! No need to for you measure spring space.

Maximum preload= (spring travel) – (shock travel)

• Product Extended Length: 20.040
• Product Collapsed Length: 14.550
• Product Travel: 5.490
  
  3.0 x 14" x 650lb spring has 7.39" of spring travel

7.39" - 5.490 = 1.9"

 

Its not so complex.

6.61 inch is solid spring height (ie coil bind)
14 inch is free height of the spring.

Subtract the 6.61 from the 14 to yield 7.39 inch spring travel. It would take over 4800 lbs to compress the spring to solid height.

You need about 1.9 inch to support the weight of the truck. Subtract the 1.9 from the 7.39 yields 5.4 inches travel before solid height.

 

The reason is my most likely that my truck is more superior than yours.

 

you wish lol

It would be cool to compare all of the data points between yours and my truck on the ADS vs fox and see exactly what it is that makes your setup different than mine for preload and all that.
But that would involve more work than I'm interested in so I guess it will remain a mystery.

Yea I gotcha. It makes sense now after all your guys' help.

I measured last night and the passenger side is at 1.75in of preload and the driver is at 1.9375in of preload . Not as bad as I thought though. I thought it was going to be over 2 or so.

So I'll take out some out of the driver side and drive it for a bit and see if I feel like moving to a 700 and getting it revalved.

 

I’ve looked all over the place for a source of reliable and complete specs for spring and shock specs (spring length, spring rate, shock extended length, shock collapsed length, etc) for king, fox, arb, oem, etc parts and have never found one. There is a lot of incomplete and contradictory info on the web. Do you know of a decent source? I’m primarily interested in king, but it would help me help others if I had specs for the others.

 

Does King not use Eibach coils?
Do they make their own?

I know that fox and I believe ADS use Eibach springs