Seeking Advice on 4runner Rear Spring Options

Neosapian

Member
Howdy!

I'm working on outfitting a 2008 4runner 4.7L 4x4 Limited with 130k miles.

Sitting in the garage collecting sawdust is a set of 285/70r17 Cooper ST Maxx's on alloys... I cant mount them until I lift the truck, and I'm hesitating on the lift purchase because I can't sort out which rear spring rate to choose.

I will be going with the Old Man Emu 3" setup. Probably front top spacer, definitely Nitrocharger shocks, and heavy front spring to accomodate the weight of the V8 as well as a secondary Yellow Top and Warn VR-10S on a Budbuilt Hidden Winch Mount. Demello front bumper will happen eventually, but it is a low priority. I'll be replacing the rear bumper first. More on this later...

I've already spoken with a local ARB rep, and I've researched the topic at length. I'd really appreciate some advice and opinions on the 440lbs. vs. 880lbs constant-load rear springs, taking into considering my specific load requirements. This is a particularly important decision for me, as I will have a considerable amount of weight over the rear axle when fully loaded for a long distance 4x4 camping trip, but also use the truck for my daily commute and light duty forest service roads for hiking and snowboarding.

Here's how a typical weight loading over the rear axle will approximate:

Total Minimum Loadout For Remote Off-Road Camping Trips Is 600-650lbs, Over Rear Axle

*This figure does not include the 120lbs (13-15 gallons) of water in a poly tank mounted between the passenger frame rail and drive shaft (where the OEM muffler once was). This will have around 55% weight bias towards the rear axle.

*This figure does not account for a rear bumper & swing out, which will add an additional 130-200lbs depending on design and materials. I am leaning towards a custom setup using 1/4" steel skeleton for load bearing/mounting elements with a "sacrificial" 3/16" plate aluminum shell. This is still just a napkin sketch, however.

My General Thoughts on 440lbs vs 880lbs Rear Springs

  1. There will be 15 gallons of gasoline (135lbs w/ tank, mounts & aluminum bash plate) in the OEM spare tire location. This weight will decrease as fuel is consumed. As will the 15 gallons of fresh water weight. A reduction of about 200lbs.
  2. Payload will decrease by ~300lbs while empty during ordinary commute & weekend Wheeling.
  3. Should I over-spring the rear by 20% for fully loaded trips, and deal with a potentially very bouncy tail end when unloaded? Or should I under-spring the rear by 30% when fully loaded, deal with increased pre-load or potential "sag", but benefit from softer rear end and better road manners for the 95% of my normal driving conditions?
  4. I do not want to add airbags. I prefer to avoid mis-matching spring & shock manufactures.

Am I approaching this logically? If you guys were/are in my situation, how would you advise?

Thanks for your time!
 
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Watt maker

Active member
I would base the decision on how much you anticipate being loaded down versus how much you will drive it unloaded. If it were me I'd go with the heavier spring.
 

Neosapian

Member
Thanks for the response.

An ARB rep said I should be "okay" with the 440lbs springs, but Im a bit doubtful.

80% of my annual mileage is the basic commute to work, snowboarding in the winter, and forest service road access for backpacking in the summer. This is all light-duty stuff. However when loaded for a 2-3 week trip that includes several hundred miles of off-pavement travel, the weight and demand placed on the rear will increase dramatically. 250-300lbs vs. 600-700lbs.

I am a conservative driver off road. My Girlfriend and I can live in the backcountry for a week with 32lbs of gear on our back, so we pack light - even when truck camping. As we all know, every ounce counts - and these trucks reach GVWR pretty quick without much effort...

Anxious to press Buy on the lift but could definitely use some more encouragement and opinions.
 

ttfjc

weekend wheeler
have you looked on a 4R forum? i'm sure your exact set up has been done 10000000000 times before.
 

Neosapian

Member
Thanks for your suggestion TTFJC.

I am a T4R member and I've looked long and hard. I don't know of anybody on T4R Forums that is running OME Suspension, with the exact same setup. Rear winch, 15 gal fuel tank and 5 gallon grey water tank with 1/4 aluminum bash plating in the OEM spare tire location doesn't seem to be a very common configuration for 4runners.

Its easy to find advice on which spring to buy based on an approximated fixed curb weight. Not as easy to deterine if or how to under or over-spring a vehicle with fluid weight that can vary 200-odd lbs throughought a trip. And over 400lbs difference between commuter mode and vacation mode.

Many people don't bother to itemize and weigh all of their gear, hardware and mods. Springs are specifically tested & rated. Mine will hopefully best match my intended use.

I reckon If anywhere, Expo Portal is the place to go for technical advice. One more call with ARB before i press buy.
 
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daPitbull

Adventurer
Those springs rates seem really high, especially for a constant rate.

I’d look into progressive rate springs or air bags. Those will be too heavy for DD, my opinion. I’ve got a built 08’ too, and I pull an off-road trailer.
 

High Country Nomad

Mountain Explorer
The 440 pound springs should be fine. I bought these http://iconvehicledynamics.com/shop/4runner-coil-springs/502-4runner-overland-lift-rear-coil-springs.html for my 15' 4Runner paired w/ BP-51 suspension. When I run empty the driving experience is pretty close to my loaded experience. When loaded that includes - 2 kids, 1 big dog. Fridge w/ Grill Slide, rear bumper, 14 gallon water tank. Bags, and a roof rack full of wood, chairs, etc, and and bikes on the rear hitch. I have the 440's on my Cruiser and it's the same situation, loaded and empty aren't very noticeable.
 

Neosapian

Member
@High Country Nomad and @daPitbull, I agree!

A few days ago I had a very insightful consultation with a rep at ARB Australia's Melbourne location. His advice differed slightly from what I received from ARB America.

Conclusion #1: Avoid the heavier 886 front springs. The multiplying effect of unsprung weight leveraged behind the rear axle will reduce front spring pre-load, exaggerate negative rake and could reduce front up/down travel. This raises concerns about off-road traction as well as daily ride quality. "Medium Load" 895 Springs are sufficient for 70-180lbs, and although my front weight will exceed this rating, only a portion of it is distributed on or ahead of the axle itself.

Conclusion #2: Medium Load, 895 Rear Springs with Air Bags for load leveling is what ARB Australia generally suggests for a built but daily driven Prado/4runner. The alternative to bags would be their medium duty spring, with the less commonly paired Nitrocharger Sport (60005) rear shock that represents a 15% increase in valve "stiffness" over the commonly sold 60004 shock. Firmer shock for better rebound and lower shock operating temperatures in loaded off road conditions without the steroidle spring rate and bounce of a OME's heavy spring during the daily commute.

If I discover later on that I absolutely need a heavier sprung rear - I'll already have the corresponding shocks, and the Icon (progressive rate?) Overland setup seems to be sourced from the same manufacture with the same final spring rate of the heavy OME's.

This advice is completely contrary to 90% of common wisdom found online. Many, many 4runner and FJ owner's are focussed on a level ride height above all else, as apposed to a truely dialed spring/shock match that may possibly induce some perceived bro lean or pre-load when fully loaded.
 
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ttfjc

weekend wheeler
simple solution. Just keep your car loaded and ready to go at all times and then it will always be the same weight:clapping:
 
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