Roll center

So I'm setting up my control arms and my steering rack is mounted and the lower control arm is set into position at a 10* slope (4.5" ride height 2001 Silverado) Now with my upper control arms pivot inline with my tierod and LCA this puts my roll center at 3" below ground. I know Herb recommends -1 to +3. Am I at a point where I need to re engineer this or what could become of something like this?

First off, this part of the job is the design work, once you start building the parts to be strong enough to live then you're engineering.

It would be advantageous to run a drop knuckle, but not necessary. The drop knuckle (or more drop if you already have one) will lessen the angle of the arms at ride height and raise your rollcenter, but unless you plan on really driving this thing hard, I don't think that you wold need to worry about it. You would probably feel more of a difference if you just ran high quality shocks. Calculating rollcenter is getting pretty involved on an adjustable suspension vehicle that will probably never see the track. I am however impressed that you are taking it into consideration, as it IS important that the instant center is on the opposite side of the vehicle, otherwise you will never keep camber under control.

Its nice to see someone putting some true engineering into their ride!

thanks for the input Max, and yes I really want to make this right... I do plan on really driving it because it will have a high horsepower 700HP +/- But not really the track. My instant center ends up somewhere about 16" from the opposite sides tire center. So the three inches below ground should have little to no adverse effects? My LCA and tierods are at a 10* and upper just about 20*

Your A-arms are a bit steep for my taste, especially on something that is going to be driven hard, but again it will most likely work fine. The short IC tells me that you're begining to run the suspension beyond it's intended working range and camber gain will start getting excessive. I would suggest drop spindles if you want to want as much performance as possible, they will reduce the camber gain rate and give a more desireable roll center.

i do have drop spindles, I think it's just the fact Im running such a low ride height....

No. Probably because you are running a 30+ inch tall tire.

Edited: 6/20/2008 10:35:40 PM by GMracer

275/4028.66"

I'm going to mess around with it, double check everything and see if I can get the angles to come down... but I am technically setting it up for a 7" front drop... so maybe ride higher, and lift the rack to allow the arms to move upwards.

Is this a custom build? If so, you should try to set it up so that you have about 1/2

Yes full custom chassis, on bags, but I was trying to keep the rack in the stock location since the it sits tight up against the motor as is. But sounds like the only way to make it right is to raise the rack... I should have about 9" travel up front, and my ride height is 4.5" so I am setting it at half travel. Without the drop spindle I was at 14* and 33* they drops helped a little bit but not as much as I was hoping for. I'm going to work on it some more and see what I can come up with, I don't want to have to raise the engine that much if I don't need to