Long Travel BS Thread

I ended up with 40” lowers and 35.5” uppers ( not measured on their angle, just straight from axle to frame)

this is how my mounts are set up give or take noise.

 

I’ve only been guessing at numbers too, I don’t actually have the parts in front of me to measure so that could be Most of my issue for the axle end of the measurements.

 

40” links are super short, what kind of travel # are you looking at ? seems like your drive shaft plunge is going to be extreme with such short links. typically a dcsb uses a 52” link

 

Just under 25” of travel. I do a lot more rock wheeling so shorter links were a better way to go for me. We will see what happens to the drive shaft

 

Busted Knuckle’s four link videos on YouTube are very helpful and easy to understand.

 

Anybody have any fun with the JD SUA kit? Thinking thats a good option for a stage 1 rear long travel setup.

 

Is there a shorthand way to approximate ride height after a coil swap? I’m going from 16” 600# to 18” 500#. I hate making preload adjustments on the front. It’s a lot easier on 16” coilovers haha

 

How much preload is in the 600# springs? Not exposed threads, actual preload. Knowing that # will give you the amount of spring force required to achieve your current ride height. You can then divide that # by the 500# spring rate to figure out how much preload you'll need in that lesser rate spring. It's not an exact science but will get you close.

 

I'd think comparing the ratio of spring rates in relationship to a current measurement + any change in spring length will give you a ballpark number. Would have to account for the motion ratio for the shock in the middle of the LCA in there somewhere

 

I’m an exposed threads kinda guy, but I’m assuming measure the coil when off the truck and still on the coilover and it’ll tell me approx how much force per inch? Say it’s compressed two inches so 1200#. If I didn’t adjust the collar I’d need to compress the new coil 4” so that would be 2000# which is too much. Going by this train of thought I’d only need to compress the new coil approx 2.5” or move the preload nut up 1.5” from its current location.

 

If I want to match my current ride height I wouldn’t need to account for the motion ratio since whatever force I’m trying to match will be the constant, right?

 

You're not going to have much adjustability if you put on 18” springs due to the block height on them if you want full travel. You'll have enough to level out the truck and that's probably it. My truck on 40s and 18x500 has the frame sitting at around 21-21.5" off the ground. When you put a 18" 500lb coil on a 8" long travel shock you end up preloading the spring 2" or 1000lbs just to get it installed on the shock.

 

Yeah I started with 18” 600 and you’re right it takes a good bit just to get it on the shock. Maybe it’ll be just right. I’m no stranger to the coil swapping game unfortunately haha

 

Exposed threads don't tell you anything unless you're comparing identical setups with all other variables consistent. But yes, preload is the difference between the TLG of the spring and the spring mounted on the C/O, so you're on the correct path. You don't necessarily have to take the coil off the truck if you're shock fully extends at droop. Not all setups do though so you have to make that decision for yourself.

Your example is accurate though. You seem to understand the concept. You'll have to move the preload collar up to compensate for the additional length of the new spring. Which is one of the many reasons that exposed threads isn't a good unit of measurement.

 

This idea is correct. The numbers show that he may be able to make it work depending on how much preload he needs to obtain the desired ride height. The block height on this particular springs is 8.43" w/ 9.57" of travel. Assuming he's using the JD spec C/O and using the full stroke (which he probably isn't with a 2.5" kit), the max amount of preload will be 1.92" before he binds the coil. Eibach's catalog below for reference.

 

Very cool. Yes, it’s the jd specd Fox coilovers. I’m strapped before it’s fully extended. They’ve gotta come off to clear for 37s and swap coils so I’ll take some measurements. I’d imagine there’s quite a bit more shock shaft left before I am at full bump so probably a bit more coil bind wiggle room could be had. Not the end of the world to make adjustments.

 

That was my experience. You don't use full bump travel unless you cut out the factory bumps and relocate your bump height so in theory you should have a bit more room to work with in regards to preload. I also doubt you have 2" of preload in the current setup. I'm only at .75" of preload with my 16"x600s.

 

Yeah I remember it being a lot easier to get onto the shock so I’m probably right around where you are.

 

One thing to note about the 2.25 kit is that the upper uniball maxes out and leaves 1-3/8” exposed shaft and that’s taking into account the lower coil perch. So that gives more adjustability with an 18” coil.

 

I’ve notched the cup a bit on mine after hard hits so I might have to space the bump stop down a hair. Not opposed as that’ll make clearing the 37s a wee bit easier.