wow great thread with allot of interesting points on suspension theory and geometry from what i get is that the torque arm has absolutely nothing to do with IC its all about lca angle because the only thing pushing the car forward are the lca's and the angle in which they are pushed forward via rear axle determines weather the tires are going to act against the weight of the car forcing the chassis up while pushing downward ie the lca's on an upwards angle or forcing the chassis down and acting against the rear springs making the rear axle to want to lift causing wheel hop
i don't think changing the height of the ta mount effects any thing other than pinion angle because the only purpose of the ta is to keep the axle from rotating the reason why its so long is to minimize the amount of axle rotation through out suspension travel
also the effects of toe angle while cornering due to lca travel is very interesting but i wounder if the body rolls enough to have a significant effect on the thrust angle of the rear axle

 

Okay; JR Warrior- I'm going to stick my neck out and '''''wonder''''''' why you selected this particular thread to be your first to send a notation on. Can you share what viewpoint you are/were researching from that made this type of maddening thinking appropriate for you?
I'm a hands on the the item, making them move through their paces that gets my little o' brain peanut to grasp any suspension theory, and I have to do that for almost each specific approach to be able grasp them all. I had a subscription to Circle Track mag. for four years as a way for me to understand suspension basics. I didn't learn a thing. I would have been better off working in a gas station during all that time my family prayed for me to give up Satan's playtoys.....!

When I was 8 or 10 years old, without understanding it, I could watch the way the cars did their burn out that told me who was basically going to win a drag race: would the tyre torque lift the back of the car up or would it pull it down into the track.

What are you looking for on your smoking hot-rod? This year it becomes legal to drive in spite of some short-cuts I'll have to take. There's definetly more suspension designs to explore as the torque levels go up!

 

i have been an ASE certified mechanic for 14 years steering and suspension is one of my certifications and like you im a hands on learning type experience is the best teacher there isn't a year make model car that i haven't aligned and I've built plenty of track cars to know what i'm talking about and yes this is my first post making me a JR as far as posting goes but i'm no novice when it comes to cars sorry if my explanation seems like madness to you ill try a different approach
if you take a screwdriver and place it in between the palm of your hand and a wall with the screw driver at an upward angle then push notice that your hand wants to travel downwards and the tip of the screwdriver is forced upwards that's a good example of what the rear axle rep by your hand is doing in comparison to the chassis of the car rep by the wall
and that is what anti squat is
notice when you see a car that is set up right launch the nose lifts but the rear stays level and doesn't get out of shape after 20 feet or so
a car with to steep of a lca angle tends to lift the rear chassis on launch and actually make the tires loose traction after the weight of the car is no longer being transferred properly
my car wheel hops like crazy especially after converting from a 700r4 to a t-56 because the of all the deflection in the stock lcs's and torque arm plus the fact that our cars have very little if none anti squat designed into the suspension so the relocation kit as almost a must if you want to get on the gas right off the line especially with a manual trans
my car is a dd and will never see the track but it sees plenty of hot rod Harry's pulling up next to me at a light thinking there new mustang or bmw stands a chance lol

 

Don't worry, great explanations, and glad to have more people to meaningfully add to the conversation!!

 

That screwdriver visual is the best I've ever heard; thank-you. The relocation kit is the ONLY standard suspension upgrade I havn't done yet; that, and select a pair of rear shocks that work. My rear end is very loose at the point I left it and dived into a new engine redesign that was California AND TPI legally maxed out. Fortunately I just bought a house in a non smog compliant zone so I can go ahead and put it all together this year a little cheaper than normally. I chose to stay with the factory auto that came with my IROC; there's already so much of these cars that has to be replaced as it is.
I bet this rotten economy has been clearing the roads of used 3rd Generations by the tens of thousands every 12 months....
Have you thought of what you'll do to maximize the anti-squat as you're using yours for actual commuting chores? (this is where I'm dragging my feet on the rear shock choice...)
did I mention that I really like your screwdriver example??? Quite Succint!

 

i try to think things out in the simplest terms because some times you could get lost over thinking and when that happens you just have to say to your self keep it simple stupid
i plan on setting up some kind of marking system on the rear shocks to see how far down the rear end squats on a hard launch then removing the springs to replicate that height on the lift and set the arms even with the drive line at full squat so i could use that as a good starting point on what angle the lca's should be
I'm eventually going to replace my tweaked lg4 with a 355 C.I vortec so i'm getting every thing on the car ready to work well with the added power i squeezed 260 hp out of my 305 with stock heads which is plenty of power to move the car along nicely but i miss the feeling of being pined to the seat through out the whole rpm range

 

Iv had a ladder bar set up on My 92 Z28 for the last 20 years (from day one)
and i still use the lca. HAS the maker of the Ladder bars. points out to use/keep them.
one top name maker is Lakewood (there are others)

is seen alot of info posted.. some right. some no so much..lol.

thats what makes reading this stuff so much fun.

My car is a track car. that i drive on the street. fri/sat nights.
or take it to work in the summer some times. has never seen rain or a dirt road.
also it sits at the stock hight. not lowerd..yes i run a neg pinon angle. neg 4 degs total.
for my auto trans. and i love the way my ladder bars. makes my car Plant the rear tires. and pulls the wheels. it just JUMPS Forward and Runs strait! and its been doing this all its life.

thats what works for me

 

Just did mine....UMI units..welded in.

Beefy UMI units....heavier gauge steel than the stock brackets!


Before...car dropped 1" :


After...note new arm angle :


You can really feel the rear plant now on acceleration....hooks!

 

Hey I had a question about my differential mounting. My neighbour crashed his 91 mustang and is now parting out his car. I want to buy his 373 posi off of him and i was wondering if it would fit on my 89 camaro rs? Also wondering if i would have to do any cutting or anything certain to make it fit?

 

Just curious. According to the UMI instructions, the lower control arm is to the lower bolt on the LCARB and then it says both positions are possible. I see yours is at the 2nd(upper) bolt position. I mounted mine at the bottom position. Just looking for insight. Thanks in advance.

 

Whichever hole ends up getting you the most horizontal (erring on having the rear lower than front if horizontal isn't possible) you can get.

 

Just got my brackets from siphon - worked wonders. Went from wheel hop at half throttle launch to impossible to make it hop. Must have!

 

Has anyone experienced umi lcarb that touches the e-brake cable bracket?

 

yes I think the e-brake bracket needs to be cut it should say in your paper work that came with your brackets.