what kind of an angle does everyone's rear lower control arms sit at when on level ground? my car sits a bit higher than it probably should due to being a stripped down base model with new Moog IROC replacement springs in it so i keep thinking that the control arms should be pretty close to level or even higher on the front pivot, but both rear control arms sit at a downward angle where the front mounting point on the body is about an inch lower than the rear mounting point on the rear axle as measured with my trusty Craftsman 30 foot tape measure.

every other rwd GM car that i've ever owned has the lower control arms pretty much level at static ride height, and maybe a little upward to allow for cargo and passengers. i've always read and heard that the control arms should be level for maximum bite on acceleration and around corners on a triangulated 4 link, but these torque arm/panhard bar rear suspensions are new ground for me. is it something the GM engineers did on these cars for handling purposes because the torque arm is what dictates the pinion angle and transfers the rotating motion into the body and they point the arms down for better bite in corners or is something really, really wonky in my particular car?

the panhard bar sits almost perfectly level- maybe 1/2" higher on the body side with a full tank of gas- and will be level once i get around to chopping the springs and dropping it down..

 

These cars came from the factory with defective geometry.

The axle end of the LCAs should be slightly lower (emphasis on slightly) for most typical uses. Maybe ½ - ¾" lower toward the rear. If they are level or higher, the car will almost certainly wheel hop severely under acceleration; and if they are too low in the rear, it may wheel hop under braking. (if the car has rear brakes that actually work... not by any means a certainty in these cars in stock trim)

I have no idea why GM "designed" the suspension with faulty geometry. I doubt it had anything to do with the car's behavior though; probably more like, something about it fit some machine or fixture that they already had or re-used some part that they already had a billion of on hand like the front control arms did, and they were too cheeeeeep to be willing to make it right.

The cure is LCA relocation brackets.

 

the rear arms are carried over from the G bodies- and those were carried over from the 73-77 A bodies- but that has nothing to do with the mounting points that they are bolted to. the F body chassis was considered a great handling chassis at the time, so i'm sure there was some sort of a method to their madness..

all that being said, can anyone say how my car compares to others? it bites and goes when i get on it, and it just flat stops when i push the brake pedal and all 4 of the LS1 brake calipers bite down. it takes corners pretty good, but the shocks and struts look to be original and seem to be getting worn out so i can't really say how good it actually handles.

 

With anything resembling a stock spring they should be parallel to the ground or slightly lower in the back, have you ever seen a ad photo of one of these cars from the early 80's? They came off the showroom floor looking like 4x4's. This is my '87 which still has factory tags on the springs and surprisingly they haven't sagged much, and this is with the rear spring isolator pulled and with 28" tall rear tires (275/60-16 drag radials), meaning that the tire to lip gap is smaller than what it would have had with factory tires:



82-85 cars sat even higher, and I believe later cars were shown as lower to make them look better in adds.

All that said, even if you lower them quite a bit you shouldn't get 1" difference between the front and rear pivot points + a slight downward angle towards the front actually has advantages in a handling situation (slight toe in on turn in making the back end more stable) AND shouldn't cause wheel hop unless something else is really wrong- I've posted this a bunch of times before and I'll do it again, I've never seen one of these cars with a basically stock suspension without something actually wrong/worn out/broken. People will argue that all the time and I've even had people show me "see, all new parts and I still get wheel hop" and when it came down to it something was wrong (I've seen loose hardware, a cracked frame, incorrectly installed bushings... on cars that people swore to me were right and they were still getting wheel hop).

Do relo brackets work? Well yes, and no. They aren't the solution to all your rear suspension and traction woas like people make them out to be. They do move your instant center up which does result in more anti-squat which can help at the track. _If_ you have a soft enough tire to absorb that shock (think tall slicks, shorter drag radials will crush and bounce, you'll hook hard out of the hole and start spinning 10-20' out), or making little enough power that you just don't hit the tires that hard.

 

my car sits about like that, but with 26" tall tires all around. the control arm mounting point on the body is lower than the mounting point on the rear axle. like i said, it drives and handles great with no wheel hop or any weird shenanigans when getting on either pedal really hard- other than the slightly worn out shocks and worn out tie rods and what not in the front, it's actually pretty damn planted- but it just strikes me as goofy that the mounting point on the body is lower than the one on the axle with the body sitting as high as it does..