I glanced over that thread and read FormulaRedline's explanations. I agree that the horizontal forces of the car are transfered into the a-arms rather than the shock mount.

However...

What about the vertical forces from the travel in the suspension?

Wouldn't the loading and unloading of the car from the shock/springs cause the shock mount to move in relation to the rest of the chassis?

 

You'll have to pardon me because my suspension terminology is still really noob, but if I think i know what you're talking about, the shock mount at the top should be bolted right to the chassis at the top, so it shouldn't move independent of the chassis.

The vertical forces are, for his example, equal to the force downwards caused by the chassis load. It's necessary to have the upward force, otherwise, your wheel well would just hit the tire (right?) when your chassis bears down from the load in a turn. Someone correct me if I'm wrong.

 

Two things here:

1. The vertical load is just that...vertical. It does act in a way that creates a moment to bend the chassis. There is a small horizontal component that results from the shocks not being exactly 90 degrees vertical, but...

2. As stated in that thread, this small horizontal component acts across a moment arm that goes from the top of the shock tower only down to the large brace that connect the upper a-arms. So it can only bend from that point up...which doesn't effect your suspension geometry.

 

I agree with you that having the top of the shock tower deflecting may not have an effect on the suspension geometry. Also, I understand how it is highly unlikely that there will be enough force to cause the shock mounts to move closer together in the horizontal plane. (Thus rendering a strut bar useless)

However, would it not benefit the car to have the shock mount constrained such that it cannot move vertically so that the dampers travel will be the same as the travel in the suspension?

This way, the dampers will absorb all of the energy rather than having the shock mounts deflect and absorb a part of the energy.

 

It is a street car, not a heim-jointed race car. The chassis flex is minimal for a street car, and NOTHING compares to a properly designed race car. The difference in deflection from the shock mount is negligable, and all of the many street oriented things (like non-rigid motor mounts) are what make the car bearable for any length of time.

 

How are they going to move vertically (and for that matter, how would an STB prevent this)? We are talking about a force acting over a moment arm slightly bending the shock tower. Metal in tension (trying to push the shock tower up), especially with no leverage to multiple the force, is very strong. You do want to prevent this movement (otherwise it would mess up your spring and damping rates), but it's movements now are so small it doesn't make any difference.

EDIT: Good discussion btw. I appreciate someone trying to reason it out with scientific principles instead of the old, "Well Jimmy has one, and he felt it work!!!1" arguement

 

It would definitely depend on the amount of movement that the shock mount allows given the force that is applied. At this point we can only assume whether or not it deflects with based on our judgment. I also think that the deflection is minimal, but we have to look at it relative to the travel in the suspension.

I was looking at the X type bar that T1R and ASM makes. That design may help in constraining the vertical movement since it has those two other connections to the lower part of the chassis.

BTW: I've tried pretty hard not to use the : "ASM uses it so it MUST be AWWEEESOMMME"

 

Now my question is will the T1R or ASM or NRG X-bar fit with a Mugen carbon hood w/o rubbing/pinching??

 

Shock travel is measured on this car in inches, and I'd be willing to bet, based on the strain-stress properties of steel and the fact that the deformations are elastic (since the towers do not deform as your suspension moves up and down hundreds of times per minute), that the strain is measured in hundreths or thousandths of an inch. It's a bending versus tension situation; it takes a lot more force to stretch something than to bend it.

 

Hey I'm trying to sell a carbon one, I only want $75 its NIB

E-mail me at hdjohnson@wm.edu