Help with 4 link setup

[paint2361]

Hey everyone, quick question to ask... I'm setting up/installing a tri 4 link in a first gen camaro. I have the uca's installed perfect. But the lca's are alittle off and I just want to know how bad the car is going to ride if I leave it. What I have is about a 4* down angle on the lca from the rearend to the chassis. I know it needs to be level or at the most 1* up at ride height. I'd have to really cut into the floor or cut up really nice rearend brackets to fix this. How bad is it goin to ride? DD, autocross, time attack.... Nothin to crazy

[BillyShope]

The angle of the lower link (or, for that matter, the upper link) is unimportant. The important matter is the intersection of the link lines, which defines the location of the instant center. This, in turn, determines the percent antisquat.

I would encourage you to read Page 45 of my site.
http://www.racetec.cc/shope

[Norm Peterson]

Since hard cornering activities were specifically mentioned, I think more information is needed. Link pivot locations also define the geometric roll center and axle roll steer effects.

I have to admit having curiosity about what is defining "perfect installation" of the uppers. This is not a comment on fabrication, but on what idea of "perfect geometry" that it might be tied to.


Norm

[ErikLS2]

Not slamming the OP in any way but is there such a thing as a "perfect installation" when pretty much everything is a compromise?

[paint2361]

Nothing is perfect in life! As for the uca's, I had a real hard time getting the rearend centered... So now that it's centered I'm goin to say the arms are perfect:) That's all I ment by saying that..

[Norm Peterson]

If your lowers are parallel to car centerline in plan view (as I suspect they may be), I'd try pretty hard to get them closer to 2° down in order to put the roll steer at a better starting point. If possible, consider trying to make up some of the change in inclination at each end of each LCA instead of all at one end. I suspect that the combination of plan-view-parallel and 4° down for the LCAs is going to be a little clumsy when asked to do slalom maneuvers.


The question I should have asked first - is that 4° down angle measured with the car at full weight including at least some fuel in the tank? Half an inch ride height difference probably translates to about a 1.5° change in LCA inclination.


Norm

[paint2361]

Thanks for the info! Good stuff! Right now my rear end is welded I to place at ride height. I guess if I have to I could just raise the right height to get that lca closer to a 2* down angle.

[paint2361]

I had decided to try and draw out my rear 4 link on paper. From what I see my IC falls about 22" behind the center of the front axle line.
With just an estamated CG line my IC is way below the 100% anti squat line. From what other people have seen on here I'm wondering if I'm around the same ballpark?

[Norm Peterson]

Draw a line from the rear tire contact patch through the IC and extend it forward to the front axle line. The height where this construction line crosses the front axle line divided by the CG height is the % anti-squat.

Very roughly with some mental math: for a PT sort of car, if the IC you have now is about 10" above the ground, it's at least reasonable for the purpose. A more dedicated dragstrip car would probably have the height of an IC at the same longitudinal location closer to 16".


Norm