Rock

I picked up Doorslammers (the Chassis Book) and there is tons of great info in there. Now, trying to apply some of the info to our cars is pretty challenging.

Out in the back we've got a pair of control arms, a ladder bar (tq arm), springs, shocks, panhard bar, and a brace that ties the rear subframe together.

Would our rear suspension setup be called a modified 3-link? Is there a real name for it?

Since there aren't any upper control arms, there is no imaginary instant center. The point that the torque bolts to the frame is the instant center, period. The torque arm is only used to adjust pinion angle.

What are some reasons for buying adjustable control arms? The only thing I can think of is to make the track straight if the rear isn't square in the car.

Since there is no instant center influenced by the control arms, how do relocation brackets affect a non lowered car?

Please tell me if my assumptions are correct. I'm open to discuss these so we can all go faster. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

MADMAN

iTrader: (4)

You are correct in your assumptions. The need for adj. control arms are to center the wheel in the wheel well as well as square it. Depending on whose T/A you have you will need them. I am not a big fan of relocation brackets as we use the T/A as the lift point not the lower control arms. If you relocate the arms then you have 2 different arcs in the rear suspension travel which will cause a binding of one or the other of your suspension pieces.
Our T/A has adjustment holes in the front much like a ladder bar. If you move it up or down for better traction the the rear end housing tends to come forward or back in the wheel well. This is where the adj. control arms AND the adjustability of our T/A comes into play.

Keep asking these excellent questions and I would be more than happy to discuss more.

2000 Camaro SS

Madman you say you don't like the idea of relocation brackets as it introduces bind in the suspension.

"If you relocate the arms then you have 2 different arcs in the rear suspension travel which will cause a binding of one or the other of your suspension pieces."

What about when you use spherical rod ends in all components instead of normal bushings. Does this still introduce bind?

<small>[ March 31, 2002, 07:40 PM: Message edited by: 2000 Camaro SS ]</small>

JS

iTrader: (4)

Madman u made me REAL HAPPY with this post.I just installed a 12-bolt and since adding the 28in slick to my car the tires hitting down low in front of the lower well right behind the doors.

So I bought a set of adjustable control arms to bring the rear back and to center it even in the wells.Is this okay as long as I check pinion angle and the length of my DS to make sure the splines r in enough on the trans?

I hope u answer yes ot this becasue thats what I've done and everything lines up perfectly now.The rear is back 3/4in and the panhard was adjusted so the rear is center.I have pinion angle set at -2.5.

Any help would be great.

JS

MADMAN

iTrader: (4)

2000 CamaroSS,
It doesnt matter what style arms you have whether they are poly or bearings the bind is in the arc of travel.
JS,
You remedied your problem correctly. Thats excatly how we fix it.

2000 Camaro SS

MADMAN
Thank for the response. Forgive me for being stupid, in what manor does the bind hurt. I understand the arc travel, are you saying that this is stopping my car from sitting back when I take off at the track? What I'm asking is this hurting me at the strip? My car is 95% track. Mods below.

MADMAN

iTrader: (4)

The rear end needs to swing freely up and down. If you have 2 different arcs then the rear has to fight the control arm OR the T/A arc.

chevyguy3

iTrader: (4)

Madman, thanks alot for pointing that out. i had never even thought about that but once you think about it its obvious that that is happening, much moreso on a TA setup like yours where the front of the arm cant slide forwards or backwards, and there is no bushing flex. guess ill ditch the LCA brackets when i get one of your arms in a couple months <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Rock

Madman, your torque arm looks like a killer peice. Unfortunatly the cost of that just isn't in my budget right now and I'm not sure if it will work with the Subframe connectors I have ( I could be wrong.. can't tell by the pictures). I have the Z Rated Double Diamond type.

It looks like your torque arm brings the instant center right behind the trans, and the weld on bracket looks to tie the subframe rails together; not a bad idea. Now, while we are on this theory discussion:

Assuming I wanted to bring the IC even further forward than you had it; what if I built an ajustable upper/lower control arm type assembly that put an imaginariy IC where ever I wanted it? It would obviously need 4 mounting points, with adjustable holes; like half of a four link.

I assume it would probably place further forward than is useful. But you could also raise or lower the IC. Add threaded spherical bearings and now you can still adjust pinion angle and have alot of options for placing the IC.

Would strength be the main issue? Would there be too many non-usable combos? Have you seen or heard of anyone trying this? Unfortunately I don't have the skills or tools to experiment with this.

Fire away! <img border="0" alt="[fight]" title="" src="graemlins/gr_punch.gif" /> <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

MADMAN

iTrader: (4)

In essence you are describing a mustang rear suspension. It is a good idea.
Our T/A is adjustable in many of the same ways. We can raise the rear of the bar on the housing or lower it PLUS the front is adj. up and down. I can put your I/C anywhere from the middle of the bac seat and 8" off the ground to the front bumper and 3" off the ground.

GeorgeC

Madman, save me a phone call and answer a couple of quick questions, please...

What affect does changing the mounting location of the torque arm on the bracket have (I'm talking about the bracket bolted to the rear end, with two sets of mounting holes for the arm to mount in)? I currently have the torque arm in the lower set of holes, and the front is in the middle hole (on the crossmember). I haven't set the pinion angle yet since there's no engine/tranny in the car, but I will probably start it @ 2deg. down.

Is this sort of a "neutral" setting? I don't want to set the car on the bumper the first time down the track with the new motor and your torque arm... <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

BTW, I do have Metco LCA's and their relocation brackets, although they don't seem to move the LCA as much as most of the other brackets out there. Should I ditch these as well? They've always worked great in the past, and I could tell a definate difference without them on the car (.03-.05 worse 60' w/o them)... I hate to think of taking the brackets off, since they've been welded to the housing. It would be nice to have adjustable LCA's, though.

What do you think?

MADMAN

iTrader: (4)

In your current position the car will have a I/C about the flywheel of the motor and depending on final ride height probably 5-6 inches from the ground.
The upper holes give the T/A more leverage to lift the car. Lower less leverage. Usually I set the bar in the lower holes on the housing and set the front of the T/A down hill 3 degrees. The pinion is set at 3.5 to 4 degrees.
I would set the T/A and then without the springs in the car move the housing up and down and chec for binding. It should move freely.

GeorgeC

Upper holes give more leverage, lower holes less leverage... OK, I think I see now. I will go in and check for free movement of everything as well.

Thanks!

Rock

I'm familiar with a mustang four link. However I don't see how the one I described is very similiar.. the only simulaties would be a total of four control arms, except 2 control arms would do the job of the torque arm to simulate a longer torque arm.

MADMAN

iTrader: (4)

I see where you are going. The idea you are thing about with the four bars would take a ton of R&D to keep the bars from breaking plus I dont think you could get the instant center anywhere close. The problem would be getting the arc of the rear correct.

T
Let me think about this one you could be onto something.

GeorgeC

Madman, one last question... What affect does moving the front mount (the three holes in the crossmember) have? Thanks (again)...

Rock

Yes, I'm now visualizing some bind as the rear suspension compresses. Unlike a torque arm which has a single pivot.

Perhaps some adjustable travel limiters or rubber bumpstops could be used in a slotted track. Obviously the arc of the rear is the hold up here. Maybe I can do a few sketches to see what kind of solutions we can find.

Keep me posted mad man.

Tell me something though MR MADMAN. Would the almost infinite adjustability even be worth all the R&D?

MADMAN

iTrader: (4)

Probably not. On most of the cars we build you very rarely use more than 2 mounting points after you get your initial setting.

2000 Camaro SS

I have been reading through this post and all the others that was posted on "Instant Center" and have learned a great deal! BUT... I still don't understand if we want our cars to squat in back or not when we launch at the track. I'm supposing we want to have the weight transfer to go to the rear with out lifting the front to high but with in this do we want the rear to squat? I'm thinking no?

SILVERZZ28

iTrader: (3)

You guys are talking about centering the rear up. How are you acheving this. Are you measuring from the front tires? also I am using a stock T/A. Can I use the adjustable LCAs to get my pinion angle?