Outer Limits 4x4 Board

Ok long story short. I am making a hydraulic suspension lift for my paj. Was doing a bit of testing today and was a little disappointed with the outcome. The hydraulic cylinder works fine, where I’m running into trouble is the lift I am getting out of the car.

Talking about the front (Independent Suspension) Testing one side only

My questions: How much one wheel travel will the sway bar allow before it starts to resist the wishbones movement?


I have calculated I have to move the torsion bar anchor bolt 16mm to get 50mm lift. From what I can see I get the 16mm movement at the bolt, but I only get 25mm lift at the wheel. All I can put this too is the sway bar coming into play and the one hydraulic cylinder is trying to lift the whole front end (well… sort of, allowing for the sway bar bending etc). The cylinder can handle it, but I think the torsion bar takes all the bending.

Does this sound correct?


If I wanted to find out for sure, I should test both cylinders at the same time (negating the sway bar mechanics) – but the other one is yet to be manufactured.


Any help on this would be appreciated.

Hi Dave,

I presume you moved forward as you did the lift or had the front wheel off the ground? The reason I say this is remember with an independant suspension, as you lift it, you narrow the track width.
If you were lifting it with the wheels on the ground it'd just put more twist on the torsion bar as the wheels won't be able to more inwards.

The sway bar may make a difference if just doiong one side, it is easy to whip off and see if things change. If you lift both sides at once the sway bar will not affect it.

Those are my thoughts. How did you come up with the 16mm out of interest?

I think you are on the money though, that one torsion bar trying to lift the car is not ideal and if you hook both up you will be plesantly surprised. If one can lift say 3/4's of the front of the vehicle 25mm then both should get you ya 50mm.

I am sure Mr Physics dude Scott will be along to help answer your question properly!

Thanks for the reply NJV6,

The car was stationary. this could be my problem. I ripped out the rear springs in trying to install the rear cylinders ages ago, but didn’t want to go ahead with the installation until I made sure the front worked. The car is up on stands atm.

Thanks for your suggestion, it solves my problem. In twisting the torsion bar like it did, it proves the cylinder is strong enough, so now I should test the stoke calc by chucking the front on stands removing the sway bar and making sure I get the wheel travel expected.


Getting the 16mm stroke value > I copied the relevant sections out of the report for the project.

http://www.whiteovergreen.com/uni/OL/Cy ... Stroke.pdf


Thanks for the help

Dave
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