Strut tower cut-off for camber adjustment

[victorofhavoc]

Unless your weight transfer involves completely unloading the wheels on one side of your car, this has nothing to do with preload. The force of a linear spring is simply F = -kx, where k is the spring rate and x is the displacement. The spring force does not depend on preload, or velocity, or how what part of the stroke you are in (until you coil bind).

How long it takes for a car to settle after an impact depends on wheel rate (which depends on spring rate) and damping force. If you believe that any of this is affected by the preload of a spring, please show me mathematically how that works.

Okay...
F=-kx is true when assuming x is displaced from spring free length
F=0 on no preload spring
F=-kx on preloaded spring where F = preload total and x is the distance you compressed the spring to generate the preload force.

As a result it takes two different forces to compress both sides the same distance. The whole point of corner balance is to counteract the weight swing, but transitional characteristics are impacted by the potential energy in the spring and usually the higher side is storing more potential to keep that corner higher. Will you feel that difference? Most people probably won't, but a pro driver could.

 

[kep]

Okay...
F=-kx is true when assuming x is displaced from spring free length

Why is that? A linear spring doesn't know or care what it's free length is.

Until the spring is coil bound, the force it puts out is F=-kx. It doesn't matter if that force is from preload, static, or dynamic load. If you don't believe me, look up Hooke's law. This simple spring problem is very well understood.

 

[victorofhavoc]

Why is that? A linear spring doesn't know or care what it's free length is.

Until the spring is coil bound, the force it puts out is F=-kx. It doesn't matter if that force is from preload, static, or dynamic load. If you don't believe me, look up Hooke's law. This simple spring problem is very well understood.

Exactly, go look up hooke's law. X is displacement from FREE length. When you pre-compress a spring, you don't change its free length, you're just storing more potential energy in it to start with.

 

[kep]

Correct. But that potential energy will be stored in the spring until you remove the preload by disassembling the strut - it's reason a top hat will go flying off you just zing off the strut nut without compressing the spring.

 

[victorofhavoc]

Correct. But that potential energy will be stored in the spring until you remove the preload by disassembling the strut - it's reason a top hat will go flying off you just zing off the strut nut without compressing the spring.

Yes, exactly. But if you picture it, the top and bottom of the strut housing have to contain that preload force, right? So anything that needs to act on it from the outside has to overcome that force first.

 

[kep]

Yes, exactly. But if you picture it, the top and bottom of the strut housing have to contain that preload force, right? So anything that needs to act on it from the outside has to overcome that force first.

That is 100% correct.

Overcoming that force is when you release the preload, aka once the shock begins to compress from its full length. Once the shock is no longer at full extension, there is no preload force - since you are applying all of the force to the spring.

 

[victorofhavoc]

That is 100% correct.

Overcoming that force is when you release the preload, aka once the shock begins to compress from its full length. Once the shock is no longer at full extension, there is no preload force - since you are applying all of the force to the spring.

Yes, this is true. You will have varying shock travel and initial load required to move the spring. Under hard braking, one side will bottom out sooner than the other. A more extreme example is my home track where the main straight has a hill at the end, then a kink, which leads into the braking zone. There is a lot of extreme movement here from dropping on the other side of the hill to get full droop, to needing to turn slightly for the kink @ 130mph, to suddenly braking very hard to come down 2 gears and 60mph. I can feel the front left has less travel (it's lower) and that it bumps slightly, which causes a loss of traction at the middle braking zone area. This is where the independent preload would help give more room for travel and also keep droop consistent over the hill.