Thread: Coilover FACTS.
View Single Post
Old 08-28-2010, 06:19 AM   #14

robertway's Avatar
Drives: 2012 Challenger SRT8 Auto
Join Date: Sep 2009
Location: Central New Jersey
Posts: 842
On the rear perch vs shock mount I think I understand the point you are trying to make now after looking at the picture you have above as well as from a picture in Eric Berry's build thread (friggin lucky SOB, now I know where that work of art intake manifold is getting installed )

I am understanding you to say the load bearing portion of the rear perch/mount is going from the #1 arrow below to the #2 arrow.

From the underside I guess the load bearing point that the spring presses against is best shown. And going to the shock mount would put the load up up higher "inside" the whole perch/mount piece.

Now that I think I am on the same page with what you're referring to, what is the problem I could run into using a unit that implements this transfer of load?

Originally Posted by JusticePete View Post
To raise the car from the mid-point on the coilover by spring perch 20mm you would need to screw the spring perch up 20mm. The coil has no where to go because it is captured between the upper spring seat and the lower spring seat. So the coil spacing will change as you raise the car. The inverse is also true until the coil actually become loose when a at full droop on a lift. Not only does this change how the coil reacts, it changes the jounce travel the amount of travel in the damper until the bumpstop is fully compressed. In the previous generation eXtreme coilover we made, we used helper spring to offset this. That creates different issues and there is no need to over complicate this.
I think this is where I am getting confused with the ride height/lower perch thing. I clearly understand the fixed design you guys use where the upper and lower spring perches have a fixed distance between them and that fixed unit rises and falls out of the clevis below (I think I have the right name for what I am thinking about) to adjust ride height. The part I am stuck on is in the inverted design and the notion that the adjustment of the lower perch changes the compression on the spring. I could understand that being the case in a design like yours if the top and bottom perches both resided on a fixed structure and adjusting the lower perch changed the distance between the two perches but in a non fixed design where the two perches are not on the same fixed structure/tube (not sure of the terminology here) I would think that the pre-compression on the spring would be determined by the weight of the car resting on the spring. If the lower perch is lowered, the strut will shorten a bit and the height and weight of the car will come down as well to once again rest on the spring and pre-compress it to the same length it was at the higher ride height.

As for the jounce/travel and hitting the bumpstop I think I see your point that there is a certain lowered height that is so low the spring never gets to use its full range before hitting the stop. Does the possibility exist that the spring will go solid before the bumpstop would even come into play? No clue here about the design aspects that go into solid spring height and bumpstop height so just throwing that out there.

Thanks in advance again for tolerating me here, this exercise definitely helps me to understand things and hopefully others as well.

"When the people find they can vote themselves money, that will herald the end of the republic." - Benjamin Franklin

LS3 Camshaft Swap Do-It-Yourself Instructions - 2010 LS3 gone but not forgotten!!!
robertway is offline   Reply With Quote