To piggyback on Audio3x's recent THREAD, I started thinking about the relation of spring weight to sprung mass.

Right now I am running the 2" Icon coils in the rear and as soon as I added my bumper, swing out and 33" spare to the back, I lost about 1" to 1.25" of ride height. My truck is an absolute pig (not as much as some, though ) so I didn't expect the 2" lift Icon springs to hold up to the weight of a roof rack, full belly armor, sliders and a rear bumper. I did notice the last weekend that the rear definitely bottoms out easier, however I wasn't sure if this was due to the fact that I lost an inch of ride height, or I simply need more than the 15% increase in spring rate that the Icon's offer.

Anyone have any input? I was going to look at the All-Pro 3.5" coils but those are supposedly the same spring rate as the Icons, just a bit longer. I may actually have to get some custom Deaver's made up, say 30% spring rate increase 2" lift springs.

Is there any way to calculate how much spring weight to add in relation to weight added to a vehicle? I don't think its as simple as adding 10% spring weight if you add 10% to your vehicle, although I could be wrong

Cheers!

The All-Pros are quite cheap and from what I hear going custom will be pricey. That is why I am currently riding the All-Pros. When I did buy my springs The_Josh offered to sell me his deavers but I forget how much and he has more weight then I do. If I do add more weight, auxiliary tank, fridge, whatever, the odds of me going deavers is quite high.

In summary I am very happy with the All-Pros ride and have not had any problem with bottoming out and they do well on the trail.

Your existing springs are constant rate springs correct? What is the rating per inch and how many inches of compression? If we know this then calculating what you need will be easy peasy if you can guesstimate the additional weight you have added.

Just the man I was hoping would respond!

I believe the Icon springs are 218# / in. rate - constant.

Since we know that we won't have to use Hooke's law lol. How much is your truck compressing when you take it off the stands now.. 4-5"? You need to keep it in the center of travel for normal driving and best ride. Longer spring could do it or higher rate also. Any idea how much weight you have added?

Oh yes, Hooke's Law.... of course~ hahah

Well, The bumper and swing out added around an estimated #180, the tire and wheel are another #30 heavier than the OEM spare, my Gobi rack is around #90 total, my roof tool box is about #10, Buds Beefy sliders which are like #80 each, and full Shrock skids which are just plain heeeeevy... This plus throwing a cooler and gear for a weekend (maybe another #100???) in the back and I'm saggin even more!

I have a hard time figuring out how much all this effects the weight over the rear axle. I've added a huge amount of weight to the truck which is why I'm thinking I need more spring rate.

If I have time today I will pull the truck in and see how much down travel I have in the rear.

Thanks a ton!

OME has three spring choices. One may fit your need.

-OME 2889: Medium 3” lift coils: Uses 60080 rear shocks

-OME 2898: 440 lbs Constant Load Heavy 3” lift coils: Uses 60080 rear shocks

-OME 2899: 880 lbs Constant Load Heavy 3” lift coils: Uses 60080 rear shocks

Awesome, thanks for that info. I was a bit confused for a second about the weights listed but according to OME those numbers (ie 440 lbs, 880 lbs) are actually the weight you added to your GVW which makes sense as opposed to an arbitrary spring rate #.

I'm gonna give Toytec a call tomorrow and see what they say about the OME's

Thanks again!!!!

Do me a favor and see where your vehicle sits before you choose!

Will do, I'll check it tomorrow.

Thanks!

Let me know what toytec says, I haven't had time to call them yet.

I'm still torn between the All pros and now the 898/99's (didn't even know they made them).

Sooo....

I spoke to Toytec (very helpful folks by the way) and went over all of the options. Basically, the OME 2895 springs seem like the best bet - they are a #260 spring rate which is over #40 more than the Icon (approx. #215 from what I gather).

Here is a good link for those of you interested in OME stuff, the back pages give all the spring rates, lengths, coils, etc.

http://www.arbusa.com/Uploads/PDF/on...de_current.pdf


However.... after talking to the guys at Toytec, I think I am going to give the Firestone 4135 Rear Airbag kit a try in combination with my Icon springs.

Here is the link to the airbags.

Firestone rear airbags - Toytec Lifts: Toyota Lift Kits: FJ Cruiser Lift Kits, Tacoma Lift Kits, Tundra Lift Kits, 4 Runner Lift Kits, Sequoia Lift Kits, Toyota Truck Lift Kits


This should also allow me to slightly adjust out the lean that I gained by having the spare stuck over on the passenger side.

After closing time today I plan on sticking around the shop and seeing where the rear suspension is setting currently in the overall suspension cycle.

I know a few have used rear bags. Has anyone who has installed them done any hard wheeling with them in? I am thinking this is a great route due to the fact that I can set them to eliminate my current sag, and when I load up the truck even further for camping, expedition type stuff, I can pump them up a bit more. Quite a few FJ guys run them with lift coils and all report great results.

thoughts?

1Engineer-

I got the forklift under the rear of the truck and lifted it up to check the rear suspension travel. Heres what I came up with:

Sitting on level ground, .75 Tank of fuel, 38.25" from ground to fender.

Lifted up just until tires loose contact with ground I am at 43.5" on the passenger side and 44" on the drivers side. The Icon Omega shocks in the rear have quit a bit more travel than OEM, not sure exactly how much though.

Just for fun, let me try to bust out some high school physics here and pretend to be smart before 1engineer comes back and lays down the law.

F(force) = k(spring constant) * x(displacement)

#1--Your vehicle according to your current findings (let's make it easier and average out the L/R fully extended height to 43.75"):

43.75" - 38.25" = 5.5" total compression

#2--Now to solve for the actual compression force over the springs currently:

[unknown force] = 215(lb/in) * 5.5(in) = 1182.5(lb)

#3--So to gain back the lost 1" sag let's assume you want only 4.5" of total compression with the same compression force, we must solve for the required spring rate:

1182.5(lb) = [unknown spring rate] * 4.5(in) >> [unknown spring rate] = 1182.5(lb) / 4.5(in) = ~263(lb/in)

Therefore, based on my completely uneducated guess, I would go with the OME 2895

Now to wait and see exactly how far off my calculations are

@SOcalTRAIL airbags would be an elegant solution and solve many of your challenges. Just make sure to question the FJ guys who are running them now how durable they are in the conditions you plan to run them. They are not too expensive so worst case if you are going WAY out in the boonies you buy a spare. They are easy to install.

And this @SOcalTRAIL is Hooke's law at it's finest! @eddiebx great job applying basic physics to a practical application. Your formulas are correct and your assumptions (raise it 1" to start) to apply this law are what I would do.

The only thing(s) I would recommend to @SOcalTRAIL is weight distribution. @eddiebx calculations assume the weight is evenly divided in all four corners of the vehicle. If you go this route you might want to install the rear springs first and take it for a test drive. If the rear is good and the front still seems to bottom out then do the front too. The second recommendation is additional weight:

If you re-spring the rear suspension for the existing weight that is good. If you then load 800 lbs into the back for a trip then the new springs may or may not be adequate. My next question would be - How much additional weight could you load for a trip? Airbags could take care of this issue for the rear.

So now you have solved for the rear. @SOcalTRAIL you now need to do the same test on the front to see if the existing suspension sag is the same. Also visually inspect it. How do the coils look at rest? Are they really close or do they look like they have some compression still left? When you do that, report back and myself or my new best friend @eddiebx will check it out for you lol.