Text Box:   How to setup your Suspension correctly by APC 4WD
Author: Jason   Date Posted:5 March 2021 
  Important Notes for setting up your Vehicle Correctly:
We can't Stress this enough....
  The biggest mistake we see by far is people ordering springs front and rear to suit "Planned Future Mods" or loads that are "Occasional" and not "Constant" Loads!!
  We have seen many suspension manufacturers end up with a "bad reputation" through no fault of their own due to people complaining about rough riding suspension or failed components & much of this just comes down to poorly setup vehicles.
  Front Suspension, all vehicles:
When selecting front springs to suit your lift, please only select springs only to suit current accessories fitted to the vehicle.
  If you order springs to suit a bullbar you are thinking about buying in the future sometime, you are going to hate your car.
  Fitting a front spring that is designed for a bullbar, or bullbar & winch etc without these fitted will cause big issues.
Rectangle: Rounded Corners:  TECH TALK-GETTING IT RIGHT WITH SUSPENSIONS

  A 50mm raised Coil Spring to suit no accessories will give 50mm of lift.

  A 50mm raised Coil Spring designed for a vehicle with approx 60-80kg of accessories "like a bullbar" will give 50mm of lift with these accessories fitted.

  If you do not have these accessories fitted, the vehicle may go up 60-75 or even 80mm in the front end depending on what spring is chosen and it will "Top Out" the shock or make it hit the upper bump stop on some IFS vehicles and ride like a brick.

  This will also void your warranty on your brand new suspension!

This applies to all vehicles, but for modern independent front suspension vehicles, the complexities increase.

 

 IFS Front Suspension:

IFS vehicles are always going to have a limited range of up and down travel available.

  All you can ever do is move the control arms up and down between the bump stop on compression and whatever limits the down travel or "Droop" on the front end, which can be upper bump stops on some Vehicles, but on most the limiting factor is the range of articulation in steering rack ends or tie rod ends.

  Lets say you are able to achieve 254mm of  total Travel in the front of your IFS vehicle between full compression and droop.

  In all honesty you are far better off having something around a 50mm lift that offers good suspension travel in both directions, rather than going as high as possible for the mall crawler look and end up with only a with a tiny amount of droop left and just lift wheels everywhere offroad.

  Big lifts on IFS vehicles are always a compromised setup unless you want to go to the huge expense of doing a Trophy Truck style of setup.

  IFS Geometry:

All IFS vehicles work on a motion ratio. This ratio can differ greatly from vehicle to vehicle due to the Strut being mounted at different points along the lower control arm, and mounted at different angles which changes the Motion Ratio.

  So what does this mean?

  A vehicle with a 1.7:1 front end ratio will gain 17mm of lift at the wheel with a springs that is 10mm taller than the factory coil.

  A vehicle with a 2:1 Ratio will gain 20mm of lift at the wheel with a spring that is 20mm taller than the factory coil.

  This means the Spring Length and Rate needed for different loads or heights on a vehicle can vary greatly.

  If the Springs aren't properly matched to the weights, even a small change in spring rate or length can have big impacts on the ride height at the wheel, let alone the ride quality.

  Lets use some all new D-Max or BT-50 Springs for example & I wil try to keep this simple, the factory coil is approx 570lb rate and the coil is 360mm Free Height, a raised no load coil to suit an all new D-Max or BT-50 can be a spring rate of 660lb with a coil Free Height of 375mm. This new Coils Installed Height with the vehicle sitting on the ground with 2000lb of load on each coil is approx 298mm with no accessories, and this gives the vehicle approx 50-55mm of lift at the wheel. Fit a HD coil to that same car with no accessories on it and things change a lot. A HD (bullbar and winch) coil for a D-Max or BT-50 depending on what other accessories are fitted is up to a spring rate as high as 800lb.

  The 800lb coils free height is 5mm shorter than the no load coil at 370mm, but this does not mean the vehicle will sit lower which is a common misconception people have when they just sit coils side by side. As the spring rate is higher, the HD coil will not compress as easily under load.

  Apply the same "No Accessories" load of  2000lb on each HD coil installed in the vehicle and it's installed height is approx 309mm if you don't have any accessories fitted to it.

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