How does 3 inch lift kit work?

Hello,
How does the 3 inch lift kits for our trucks work exactly? A 3 inch spacer lift seems to consist of an approximately 1.5 inch thick spacer. I am assuming that this is due to the position of the strut on the LCA. If this is the case, and I believe that it is, then if the bottom end of the strut was closer to the wheel then the spacer would need to be thicker. And, if the bottom end of the strut was further away from the wheel then the spacer would need to be thinner. It is all relative to the angle of the strut on the LCA, correct? If you guys could verify this for me I'd appreciate it.

Does anyone have any good sources that explain how this works? I am trying to write a paper on this for school; a legitimate source to back up my explanations would be awesome.

Thanks,
Sam S

 

Google double wishbone suspension geometry.

 

You are correct.

3" at the spindle = 1.5" roughly (not exactly) halfway out on the LCA.

 

This is great. Thanks guys!

 

I think this should be stickied. I've never seen this info, and it's pretty useful. My $0.02

 

Don't they teach basic geometry in school anymore?

Seriously... this is 5th grade level stuff.
You can figure it out by watching two friends on a see-saw.

 

Ok, stupid question: is there a technical/mathematical term for this? I'm having trouble putting this concept into words...

 

It's geometry, simple lever. Ever wheel a wheelbarrel? The tire is the fixed point, just like where the LCA bolts to the frame. Then, you lift from the end of the handles, say you lift up 2', the feet only lift up 1' off the ground. Same idea with the front suspension. Like BJ Moose said, good Double Wishbone Suspension.

 

Yup...

In it's most basic form, it's a simple lever.

In reality, the geometry results in a number of variables. If the strut is not perpendicular to the arm, then 1.5" won't = 3" at the end.. it'll be less.
Of course, the strut is only perpendicular to the arm at one point in the travel... and some suspensions are designed with the top of the struts canted inward so they are only parallel with the arm when fully compressed.


So yes, there is math that can give exact results. Suspension tuners use this math... but it is pretty complex... which is why everyone just says "1.5 = 3"...

It falls under "close enough" engineering for 90% of those looking for the answer.
For those where "close enough" isn't close enough, they already know the theory and have access to the math to get the exact results.