?

------------------
86Z28, GM 350, Jet perf Q-jet & chip Dual snorkel air cleaner, Edelbrock performer intake, Edelbrock headers, Edelbrock cat-back, Off road pipe, MSD 6AL, Accel Super Coil, Taylor Spiro-pro wires, Rapid fire plugs, Jet fan switch, World class t-5, Hurst Short Throw Shifter, Ram Flywheel, Center force dual friction clutch,Aluminum drive shaft, BW disc rear 3.45's & a posi, PBR calipers, Earls braided brake lines, Polygrapite bushings all the way around, poly tranny mount & torque arm mount, Hotchkis lower control arms & panhard rod, Rancho limiter straps, KYB struts & shocks, Gm Wonderbar, Edelbrock strut tower brace, SSM sub frame connectors, Jamex lowering springs, Carbon metallic brake pads, Crossed drilled rotors, Mobil 1 Tranny fluid & motor oil, GM syntheic rear end oil, K&N, Grant stering wheel, 1,200 watt system, Jet Black Paint, 91 Z28 rims, 92 wing, Tinted windows.

 

I believe straight line traction. Helps more firmly plant rear wheels when the car shifts weight on launch. For cornering, you want as close to a 50/50 balance in weight to prevent over/understeer.

[This message has been edited by Nightcruzer (edited December 04, 2000).]

 

Thanks does anyone know for sure?

 

*To forewarn everybody, I get very in depth and off the subject as I try to answer this question* The question is not as simple as it sounds. I am also teaching myself as I put this stuff into words.

I am not getting my information from experience because I have yet to perform any of these mods to my car yet. I am getting my answers from several books that I am reading. I plan on buying some aftermarket suspension parts soon, so I figure I need to do some research to understand all the suspension dynamics before I waste my time and money on the wrong parts. Right now, I am in the process of reading Herb Adam's book called "Chassis Engineering."

I'm not sure of the all the advantages of the RLB’s (relocation brackets) yet.

From a cornering standpoint, I say generally no. Let me explain.
Herb Adams says:
"By angling the effective control arm system in the side view, it is possible to steer the rear axle as the body and chassis rolls in relation to the axle housing. It is usually best to make the rear axle steer to the left on a left hand turn, because this makes the car turn less for roll under-steer." (He has an illustration to demonstrate this)

In other words, having the arm pointed down like it is in the factory location is actually an advantage when cornering. Think about how the body "rolls" into a corner, and how the control arm angle changes when the wheels moves vertically. In a turn, the outside wheel is going to move up (in relation to the body of the car), and the other is going to down. The arc of the arms is going to steer the rear axle in the direction of the turn, which is called "roll under-steer"(which is good). In conclusion, relocation brackets that lower the rear of the control arm are going to cause "roll over-steer" which is bad for handling.
But on the other hand, if the RLB’s increase anti-squat you can accelerate out of the turns faster. So your probably wanting a yes/no answer for this, but I don’t think it can be answered that way. I guess if you are turning and not accelerating, the stock LCA angle is best. But if you are accelerating out of the turns, they may be a small advantage if the arm is not excessively lowered.

One question that I am asking myself is, “Do the RLB’s really increase anti-squat???” First let me define “anti-squat.” Acceleration causes weight transfer to the rear wheels, which on many cars will cause the back of the car to “squat.” According to Herb, “It is possible to arrange the rear suspension links so that the driving force of the rear axle counteracts this squating force.” By counteracting this force (increasing anti-squat), you increase the force of the tires to the pavement, which is going to give you increased traction. There are ways to geometrically find the % of anti-squat, which I’m not sure how to find exactly on a torque arm suspension.

From a strait line stand point, I think the RLB’s are bit over rated. From the statics of the rear suspension, RLB’s in one way increase anti-squat, and in an other way decrease anti-squat. Which is greater?? That is what I am trying to figure out. Lowering the rear mounting point increases its anti-squat from the control arms. But, it also increases the length from the axle center line, which is going to take away from the “anti squat” of the torque arm. What I am trying to figure out is if the increased anti-squat from the control arms is enough to overcome the anti-squat taken away from the torque arm. That would tell me if the brackets are an advantage or not. I’m sure that there is a fine line to this, meaning that lowering the control arm a little will help, but too much will take away. I’m sure that different combinations will require different positions. The ultimate way to change the LCA angle would be to raise the front mounting point on the body of the car. That way you could gain anti-squat from the LCA’s w/ out changing the length from the axle center line to rear mounting point of the LCA so you wouldn’t take away any anti-squat from the torque arm. But this would be very difficult to do.

For increased anti-squat and increased traction, I think a better place to start is with a shorter torque arm. According to Herb, “The shorter the torque arm, the more the anti-squat it will produce.” In my opinion, any full length aftermarket torque arm is a waste of money. I can think of only 2 small advantages of a full length aftermarket torque arm. Number one, it allows for pinion angle adjustment. The second is that it is more rigid to handle higher torque levels. (Having some flex in the torque arm isn’t bad if wheel hop doesn’t occur, it kind of “cushions” the tires. Think of slapper bars on a leaf spring car.) I’ve learned that a lot of the aftermarket parts that people buy are a more or less gimmick. So before I spend a lot of money on something for my car I do a lot of research to figure out if my money is being spent thriftily. Global West and VSE are the only two companies that I know of that sell shorter than stock torque arms. VSE stands for “Very Special Equipment,” which is the company that Herb’s and his son’s own.

One more point that I need to make about braking. During braking, the opposite physics apply. Lowering the control arm mounting point on the axle(which RLB’s do) will cause the rear wheels to “lift” during hard braking, which will cause wheel hop. Shortening the torque arm will also cause the same effect. Herb’s torque arm is different than any of the other torque arms sold. It has a shorter arm to provide more anti-squat, but it is “decoupled” during braking and a slide arm with a rubber bushing takes care of the braking torque’s. That is why I think that am going to buy his even though it is the most expensive. I’m not sure of the price, but I think it is about $700. I know, I’m off the subject and I have written way to much.

I am not done doing my research yet, so if anybody finds corrections to I said above I would appriciate the criticsm. Also, if I find more answers(specifically about the question that I ask, “Do the RLB’s really increase anti-squat?”) I will post them if this post is still active.

Well, I guess I got a little too technical and a little off the subject.

If you are interested in handling, I highly recommend getting Herbs book. I got it from amazon.com for $15 or so. It starts from the basics and builds up.


------------------
87 IROC 350, 3:42 Torsen, pocket ported 083 heads, complete Edelbrock exhaust, Most free mods, Most little mods, aluminum d/s. Edelbrock STB, SSM sfc's, boxed rear suspension pieces, urethane bushings everywhere.
Stock cam, chip, runners, base, and trans
13.94@103mph, 2.25 60'
In the works: ported SLP runners, ported base, Xtreme Cam, homemade suspension pieces, and 27x10 Hoosiers.
Hoping for 12.999

 

Here is my experience. I built 3 3/4 inch lower brackets. It made the rear of the control arm about 1 inch lower than the front. My wheel hop problem is gone. Traction is greatly improved. If I hit the throttle in gear with my foot on the brake the back-end of my car goes up, instead of down before. When I launch, it feels like the whole car lifts, mainly in the front, but some in the back. Before the back would sink and hop like crazy. High speeds 125+, the car is rock solid. Even across bumps and the crappy roads around here. Cornering is much better and easier to control. I go into the corner harder than before, then let up a little bit causing the back-end to come-around some, then full throttle again and the rear plants hard and launches me out of the corner. Before, it was the opposite, added throttle would make it loose and the rear end would try to come-around and spin me out coming out of the corner. It's much more predictable now.
The effect of LCA relocation brackets will depend on your suspension set-up. My 82 has a stiff enough suspension and chassis to have very little body roll, which will decrease the effect of 'roll oversteer'. Since most aftermarket suspension aren't the same, I would get adjustable LCA relocation brackets and use the setting that works the best.
Having the front of the control arm higher than the back causes some of the forward energy generated by the axle to be used to push the rear axle up away from the pavement. That's not good.
If I preload the suspension before I launch, the rear of the car moves up about 1.5 inch. Would that be anti-squat?


------------------
82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

 

hey i couldnt have put that into words any better than that
only thing that i will ad is that it takes a little while to learn your car after doing that because it is a big change after i had done mine the first time i tried it on winding roads it felt a little twitchy now its just better

 

I've read all the books. Books are good, but they aren't everything, nothing beats hands-on testing.

For cornering performance, the best LCA setting is horizontal with a very slight downward angle. This is how the cars come from factory. Dropping the LCA lower will induce over-steer.

Now, anyone who has their car set up for cornering, has their car lowered. Lowering the car changes the LCA geometry. It causes the rear of the LCA to be higher than the front of the LCA. This is bad! Therefore, the LCA Relocation Brackets are installed so you can reposition your LCA geometry back to stock. The center hole in our brackets will do just that on a 1-1.5" dropped car. Cars dropped 2" will need the lower hole to get back to stock.

On cars that are NOT lowered, and are looking for straight line (drag strip) performance, it's a different story. The LCA Brackets should be used in the lowest setting. It changes the instant center of the rear suspension, and literally drives the rear into the ground. You can feel, and if watching, SEE them working.

The entire rear of the body LIFTS upon launch. If anyone thinks they do not have anti-squat benefits, come watch me, or one of my customer's cars run at the track. I have some pics of a customer I went testing with in a 98 LS1 car. The car is a 6 speed, runs our torque arm and brackets. The car only has bolt-ons, no internal engine mods, and he's running 11.9's cutting 1.62 60' times. The pics I have show the launch close up, the rear of the car is going to the sky, and the front tires are about 3-4" off the ground.

I judge if something works, or doesn't work, by the time slips at the track. If the 60' drops, it's working, the slips never lie. The brackets are the best bang for the buck suspension mod you can do as far as I'm concerned.

Herb's book is old, his company is no longer in business, Moroso bought them out. They no longer make his de-coupled torque arm. SLP used to sell them when they were still around. That arm was great for a road race set up, but not for a street car. Upon braking, the 2nd arm slaps the underside of the car so hard it sounds like a bomb going off (so I'm told, anyway).

A shorter torque arm certainly decreases anti-squat, and changes the instant center. The thing is, you don't want to go too short, or you start getting massive wheel hop under hard braking. That has been my experience testing various set ups. Our torque arms are shorter than stock, but not by an extreme amount.

Just my $0.02

Steve



------------------
Spohn Performance: F-Body Chassis/Suspension Specialists

 

IROCStan, one thing you need to consider when thinking about cornering performance as it relates to roll steer is that cornering is not a steady state condition. It is best described as 3 phases which in reality are not discrete elements like it is in books: Entry, turn and exit or to paraphase the guys who only turn left: "goin' in, turnin' and comin' out." In each phase the suspension is under different demands and should respond to these demands appropriately. For example: going into a turn on the brakes, the weight will tranfer forward, the rear axle will droop and the body will roll. The car will understeer because the front wheels will be overloaded in relation to the rear. To counteract this at the rear, a little roll oversteer under droop is what is called for.
Coming out of a turn the car will be under power causing the chassis to squat which in turn will transfer weight rearward as it rolls. This calls for rear axle under steer, which will allow more power to be used without causing excessive oversteer. The chassis tuning has a lot of variables, all of which are intertwined with one another. For example if you increase rear axle oversteer on corner entry, you will probably need to decrease you rear brake bias.
There is no correct set of parameters that will be ideal for all conditions.

 

Get ready, here comes another long and technical post by myself

His book may be a few years old, but the laws of phyics have not changed
Even though his book isn't brand new, it is far from being ancient. There is a picture of a 4th gen camaro on page 37, so it can’t be more than 7 years since the last update.

The noise that you speak of with Herb’s de-coupled torque arm when braking makes me think that it was not preloaded correctly. There is adjuster on the slide arm that can be adjusted for pre-load. Both the torque arm and the slide arm have rubber bushing, so I don’t think that noise should not be an issue. I’m not sticking up for his arm and saying that it is flawless because I have never used one. I just based my previous statement on the design only.

What kind of tires does this 98 LS1 that you speak of have? Does it have stock shocks and springs?

Steve, let me correct a mistake in your last paragraph. I don't think that you meant to say "A shorter torque arm certainly *decreases* anti-squat" but rather "A shorter torque arm certainly *increases* anti-squat." Correct? And you’re right, too much anti-squat will cause wheel hop. I left out Herb’s next sentence, which basically says that you reach a compromise when shortening the length.

I don’t mean to sound like a Herb Adams disciple, but I really think his ideas make the most sense and I don’t think that anyone else has a reputation that is comparable to his. He has been designing suspensions since the late 50’s, and is still very involved and up-to-date in the engineering world.

And you are right in saying that “books are good but aren't everything, nothing beats hands-on testing.” I totally agree. In my next couple paragraphs I’m going to give some more quotes from Herb and explain my plan of attack. I’m not trying to ram this stuff down your throat and tell you that it this is the best way to do it. But it is my explanation of his theory and I am going to give it a shot. I’ll try it out at the 1320 next spring and if it works, I’ll be sure to make a post and tell every body about it. It makes a helluva lot of sense to me. One more thing that I need to keep in mind is that Herb’s experience is more in the area of road racing and not drag racing, but many of the same principles apply.

My goal for my suspension is to decrease the quarter mile times without hindering handling, which is very hard to do. It would be easy to gain strait line traction by installing 90/10 shocks in the front and put in drag race springs, but that would ruin my camaro’s cornering. I want to do it all. I want to eat up the quarter mile on Saturday, then take the car to the auto cross on Sunday. I want pro touring. You could almost say that I am trying to cheat.

Ok, from the comments that you guys about your experiences w/ RLB’s, I think it is safe to say that they will increase anti-squat. So I will make my own set for my car because they are cheap, and adjustments are easy, so I can play around with it and decide for myself where the best settings are for different types of driving. In order to create more anti-squat, the rear suspension geometry needs to change. So Steve, if your torque arm length is basically the same as the factory piece, I assume that the added anti-squat comes mostly from the RLB’s, and a little comes from the more rigid torque arm.

This is a statement from Herb about the torque arm suspension in general:

“Since the outboard links (LCA’s) do not need to absorb the axle torque reaction, their position is not as critical to the anti-squat function. This means that they can be arranged to provide some roll understeer without the usual compromises.”

Steve, I don’t deny that your system w/ the RLB’s and the torque arm provides anti-squat and increases strait line traction. But,

"What if you could gain all the anti-squat that you need out of the torque arm only and still keep the LCA’s in the stock position?"

That way you don’t take away from cornering by inducing roll-oversteer, and can still have the benefits of added anti-squat during acceleration out of the turns. So how does one do that?? Answer: By shortening the length of the torque arm, anti-squat is increased.

But then comes another problem by decreasing the length of the torque arm. Like you said above Steve, “The thing is, you don't want to go too short, or you start getting massive wheel hop under hard braking.” Well, there is an answer for that too. Like I mentioned in my last post, Herb’s torque arm design cures that. Here is another quote from his book:

“When a torque arm is connected directly to the chassis, the braking torque of the rear axle can cause the rear axle to lift off the ground because it can pivot about the torque arm drop link. This is the same as when the side-view swing arm is too short, so brake hop will result. A solution to the brake hop problem is to decouple the torque arm so that the axle torque from acceleration is absorbed by the torque arm, and the axle torque from braking is absorbed by a different member. One way to do this is to let the front of the torque arm contact the frame only in the “up” position. This allows it to be free from the frame during braking while allowing it to transmit the axle torque reaction to the frame during acceleration. A rubber bumper can be used to soften the impact when the torque arm contacts the frame. Because the torque arm is disconnected under braking, another suspension member will be needed to absorb the axle torque during braking to eliminate brake hop. A good way to solve this is with a telescoping upper link. This lets you optimize the torque arm configuration without having to compromise it with brake hop characteristics…”

It goes on, but I don’t want to copy the rest in. I made my point. Buy the book if you want to know the rest.

Steve, I’m not trying to bash your products because they do serve their purpose. They increase anti-squat, and rid wheel hop the most simple and cost effective way. That is the goal of most consumers that buy your product. They don’t understand the physics behind everything and don’t really care. They also aren’t concerned w/ losses in rear braking. Their quarter mile time goes down, so they are happy. They also don’t want to mess around w/ drilling holes into the floor to mount a new front torque arm mount. (I’m not sure if you have to drill holes in the floor on Herb’s unit though) (BTW, I have seen one of your torque arms and I was very impressed w/ the manufacturing quality.) Also, I think that the big long torque arm is more appealing to the eye than a shorter one (ask any woman about that, hehe )

If I am unable to buy one of Herb’s arms, I will make my own. The hardest part about building it is finding a “Reese Bar.” He makes his torque arm out of a reese bar so it acts like a spring. Or I may just do w/ out the reese bar and make the torque arm rigid out some steel tubing.

Now why wouldn’t that be good for a street car?


------------------
87 IROC 350, 3:42 Torsen, pocket ported 083 heads, complete Edelbrock exhaust, Most free mods, Most little mods, aluminum d/s. Edelbrock STB, SSM sfc's, boxed rear suspension pieces, urethane bushings everywhere.
Stock cam, chip, runners, base, and trans
13.94@103mph, 2.25 60'
In the works: ported SLP runners, ported base, Xtreme Cam, homemade suspension pieces, and 27x10 Hoosiers.
Hoping for 12.999

 

Stan, look at the afco racing website. they have several different torque arm designs and a message board which is very good. One guy that posts a lot is Mark Ortiz, i think he works for a winston cup team. Their site and products are geared towards circle track, which in reality is a compromise between cornering and straight line traction.
it is www.afcoracing.com

 

IrocStan:
Before you go off on another long winded post about the engineering of certain suspension designs and components, I beg you: put the Herb Adams, or whatever other short -- decoupling --blah blah blah torque arm - just put it in the car. See what happens. PLEASE! After that, you will realise that while something may make perfect sense in your head and on paper, it is NEVER as simple when it is in the car, negotiating turns, accelerating, braking etc...

The Herb Adams torque arm is based on a sound principle - best of both worlds, or so it is supposed to be. I have seen them to be problematic at best. They are just too complex, and there is no room for rubber snubbers or bumpers or any impact absorbing devices in any race-suspension that I will ever build. In my experiance these (snubbers or bumpers) are always there to allow a cheesy or poor design to work despite the lack of good engineering.

I have seen the H.A. torque arm break, bend, make lots of noise, all the above and screw up an otherwise great handling car. A racing aquaintance of mine had one in his car, it did some of the above things and did not work as well as the factory torque arm, then it broke, so he took it out and put the stock one back in. When the H.A.T.A. was in the car you could see the arm almost scraping the pavement under braking - not good. But like I said, it is based on a sound principle, and it works on paper - just not in the car, in my experiance anyway.

And as far as the "short" torque arms go - Global West... well they are just too short. Too much anti-squat. In a car that does more than go straight, the optimal amount of anti-squat is just enough to keep the car from - you guessed it SQUATING! The back end of the car is NOT supposed to lift into the air (we are talking about corner-carving here, not straight line) The ideal setup is no squat, no lift. That way the rear suspension stays in its optimal operating range under acceleration.

Braking is a different story, because the front suspension mostly dictates what happens under braking, because it does most of the work. The Torque Arm and angle of the LCA determine stability and resistance to axle hop, but they cannot stop the rear end from lifting a bit without seriously sacrificing the resistance to wheel hop.

In my oppinion a strong stock length torque arm is the best for corners.

Lower control arms should be level at normal ride height. This provides the most predictable handling. A little roll-understeer on acceleration, a little roll-oversteer under braking. If the front of the arm is higher than the rear it definately does cause roll oversteer, and that can make a car ugly to control.

As far as the straight line stuff goes, I will second everything Steve said. Shorty torque arms are not great here iether. Front of LCA should be higher than the rear.

Corner-carving cars can do just fine at the drag-strip, for the most part, but a real drag car is UGLY in the twisties. Especially with those bicycle tires on the front

As for me, I will keep my SPOHN T.A. and lca relocation brackets. And NO I do not drag race, no offense to all the straight line guys

------------------
Karl Hunter
Hunter Motorsports
Vancouver, B.C. CANADA

 

Whoa!! Calm down!!
I appreciate you sharing your experiences even though you sound kinda rude in your first
paragraph. I agree that making things more complex often times causes hassles. More
pieces means more places to break etc. But you haven’t changed my mind. My stubborn
mind is still stuck on the idea, and I plan on making it work. I’ll build one of these “Herb
Adams, or whatever other short -- decoupling --blah blah blah torque arms” and I’ll put it
on my car. If it works, great. I’ll think of ways to make it better. If it doesn’t work, I’m
not going to give up. I think it is way too good of an idea to do that. If I have to change
lengths because I have to much anti-squat I will. OOPS, sorry. I just said a technical
word. I’ll stop before I get to “in depth.”

Me personally, I like to understand the theory behind an aftermarket part before I buy it.
Many companies sell parts by saying basically, “This will increase traction” with out
explaining a logical theory behind “why it increases traction,” or “when and where does it
increase traction.”(handling, braking, accelerating) There are so many bull chit parts for
sale in the aftermarket that provide no real improvement, or may improve one area and
harm another area. I like to know that I am spending my money on a part that I am going
to be happy with. I don’t want to find out after I buy something that “well gee, that
torque arm that I spent $400 on causes brake hop.” Herb Adams explains the theory
behind his torque arm and appreciate it. I thought that there might be some people on the
internet that would appreciate me sharing the theory with them since alot people don’t
understand how it all works. But, it seems that some people get bent out of shape when I
talk about “engineering and suspension designs” so maybe I should stop sharing my
thoughts.

Like I said, I’ll stop now since I don’t want to be “long winded”.

------------------
87 IROC 350, 3:42 Torsen, pocket ported 083 heads, complete Edelbrock exhaust, Most free mods, Most little mods, aluminum d/s. Edelbrock STB, SSM sfc's, boxed rear suspension pieces, urethane bushings everywhere.
Stock cam, chip, runners, base, and trans
13.94@103mph, 2.25 60'
In the works: ported SLP runners, ported base, Xtreme Cam, homemade suspension pieces, and 27x10 Hoosiers.
Hoping for 12.999

 

NO, Please don't stop sharing yoour thoughts! That is what the boards here are all about. And please excuse the tone of the first paragraph. After re-reading it, well yeah I guess it did come off the keys kinda rude. It happens sometimes when the fingers get going too fast - sorry.

Anyway I'm glad you did get the point about the difficulties of real-world suspension building. I'm also glad you like to understand how things work in a suspension system instead of just "hearing and believing." Too many people today are too content to just spend the money and expect improvements in relation to the dollar amount.

There is nothing wrong with talking about "engineering and suspension designs" but if you don't have the practical experiance of trying to make these concepts and designs work on a car, then it just makes the statements a little less credible - for me amyway, no offense. You gotta try stuff, and see if it works. That coupled with a sound understanding of the engineering concepts behind the parts on the car will allow you to make a car do what you want it to.

This project you are taking on is a big one. If you don't have access to a bunch of tools and a good welder, and the nesscsary experiance to use them properly, then I would say you are probably going to either get in over your head, or you will end up spending ALOT of money getting someone else to do it for you, as most of this stuff is going to have to be custom made, except the LCA relocation brackets. But don't give up, just understand what you are getting into.

If you want another great book to read pick up "How to make your car handle" by Fred Puhn. Lots of great stuff in this book.

Good luck.


------------------
Karl Hunter
Hunter Motorsports
Vancouver, B.C. CANADA




[This message has been edited by Hunter Motorsports (edited December 09, 2000).]

 

Other good books are by Carol Smith, "Tune to Win" "Prepare to Win" and "Engineer to Win"
Most of their content is based on Indy cars and Can AM cars but physics is physics. Engineer to win has a lot of practical information about hardware and some of the practical details of design/fabrication of parts. I am sure SS and Karl Hunter own these books and have read them cover to cover .

 

Hunter, no hard feelings. I think I kinda over reacted when I first read you post. I initially took it as a slam because I was all excited about my big idea then I read your reply and I was pissed because you basically said that it wouldn’t work.

Yes, I have access to some good tools. My buddy has an awesome Miller MIG welder, an old mill, and a old lathe. I wish he had a TIG welder though

I’m thinking about ideas for my T.A. right now. I’m looking at ways to improve Herb’s design. I’d like to make the length adjustable (I know, it just makes things more complicated), and also make some safety devices to keep the arm from hitting the ground if something breaks. I am also thinking about my control arms and panhard rod. Right now, they are boxed and have urethane bushings. I am thinking of making new ones out of tubular steel and using spherical rod ends so that there is next to zero deflection. That would help to keep the decoupled TA lined up.

merf23, thanks for the book recommendations. It is probably good to get more than one author’s view.

One more idea that I have: Has anybody made solid sway bar end links to go on the factory sway bars? I was thinking about using rod ends or small ball joints.


------------------
87 IROC 350, 3:42 Torsen, pocket ported 083 heads, complete Edelbrock exhaust, Most free mods, Most little mods, aluminum d/s. Edelbrock STB, SSM sfc's, boxed rear suspension pieces, urethane bushings everywhere.
Stock cam, chip, runners, base, and trans
13.94@103mph, 2.25 60'
In the works: ported SLP runners, ported base, Xtreme Cam, homemade suspension pieces, and 27x10 Hoosiers.
Hoping for 12.999

 

I have the end-links you speak of on my car they are also available at www.GROUND-CONTROL.COM These guys have lots of cool stuff for our cars.

Just out of curiosity would anybody be interested in a replacement upper strut mount made of all aluminum (super beefy) with a spherical bearing and optional raised mounting for additional bump travel? Earlier in the year I worked with a friend of mine who has mucho connections with machine shops that have CNC lathes, 5-axis CNC cutters, water-jet cutters.... you get the ides. Anyway we developed and built a limited production run (5-sets, I have 1-set left) of replacement upper strut mounts for Third-Gens. These WILL fit with Bilsteins, or any other strut for that matter and they will even accomodate custom racing struts which use a 3/4" upper mount. If anyone is interested in something like this, let me know and we will see about another production run.

------------------
Karl Hunter
Hunter Motorsports
Vancouver, B.C. CANADA

 

these relocation brackets are definatley worthwhile they are not difficult to fit (or make for that matter)
even in the lowest setting yes the car tends to oversteer a little but that is 1/2 the fun of owning a sports car it is not uncontrolable
and the traction off the corners is great
my car suffered from horrendous wheel hop i boxed the lca,s put new springs in ( 20% stiffer than iroc/ws6)
and still had the same problem
made up some lca relocating brackets and now no wheel hop at all cornering is more fun and to all you tech guys before i made them i drew the rear suspension up with the correct circles and yes it does induce antisquat !

 

How did you calculate that? How do you calculate instant center on a torque arm suspension? The books that I have looked at only show instant center on 4 links and ladder bar suspensions. One guy that I ask said that it was at the position of the torque arms front mount, another person said that it was where the LCA mounts to the car. It seems to me that it would be alot more complicated than that.

 

Calculating (predicting?) live axle geometry is actually more complex than with most IRS set ups because the axle can move in any direction in any plane. Even something seemingly minor like changing shock valving can affect the dynamincs of the suspension. This is why nothing beats real world testing.
I suggest keeping things relatively simple and do some testing with a pyrometer and a stop watch.
Rod ends are great for suspension links as long as they dont see too many miles.

 

very interesting topic, i've enjoyed everyone's comments.

Hunter: I may be interested in your strut mount. by chance to you have any pictures available?

thx

 

I will get some pics and post them.

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Karl Hunter
Hunter Motorsports
Vancouver, B.C. CANADA

 

Hunter,
What broke on the Herb Adam’s TA? Was it the reece bar?

Anyone else want to share their experiences w/ the Herb Adams Torque arm?

 

Any pics yet?

 

I used to have the H.A. LCA's and Panhard Rod in my 89 RS. I had Spherical rod ends on all of them and lets just say the ride was pretty harsh. I since have installed greasable MAC LCA's (exactly like Hotchkis) and kept the H.A. Panhard rod but I installed screw-in bushings on the end and ditched the spherical rod ends. Much better ride. I pulled a 1.986 60ft with a basically stock L98, stock 700R4, stock converter and 3:23 rear in the car. Time was 13.81@98.96mph.
I think I had the front sway bar out to unload the front end quicker for the run.

------------------
Rob P
89RSconvtZZ4TPI
92Z28convt5spd
71Impala convt 402BB
BETTER DRIVING THRU SUPERIOR HORSEPOWER!

 

Great topic guys.....Where can I find some plans for a set of relocation brackets?

------------------
1989 Iroc-Z TPI 350 auto 4-spd Removed MAF screens K & N filters, stock other than that.

 

This topic is great!

One comment about braking: From prior sportbike riding experience, I learned that braking is 95% on the front wheel(s). The rear brake I hardly used except under severe need.

I think it must be the same in cars. The physics I am guessing are very similar. And so then, rear brakes are not really super important, compared to the front braking effects. I think in my requirements, I would be willing to sacrifice slight rear brake capability for improved cornering and acceleration.

Finally, being a 3rd gen owner, the rear brake ability on our cars is infamous for being of almost useless quality anyway. So, what's the beef if rear braking is comprimised slightly for better handling/acceleration?

------------------
FORMULA 350 TK
Southern California 3rd Generation F-Body Organization©

 

Ref Herb Adams Reese Bar:

If it was slapping, it wasn't set up right, Or the car was lowered alot. What I did was just use a different bushing and problem solved, not real brain surgery to make clearance with a hammer if you wanted.
With enough rear braking, with the oem set up you can induce axle tramp. With the RB never could get it to do it.
With a 355 cheap TA radials, 3.42s, leaving from idle, big sway bars, ran 2.0s all the time.
Also, made tranny R+Rs easier, and a few pounds on the rear down low.
In 5+ years of hard use, I had no problems.
The other ones where they just reduce the torque arms length, just make a bad situation worse, IMO.
Circle Track Had a neat article several years ago about how 3 links work.
Herb Adams was a suspension engineer at GM and for a while a partner of Guildstrand. The physics of suspension design don't change.

 

To answer your guesstion, you want the axle mount an inch or so lower then the chassis end. helps cornering more then launaching.
Launching is more a function of the torque arm lenght, and pivot height above ground..

 

Update,
All that the instant center is is the point that the axle arcs upon. Instant center for a torque arm suspension is the front pivot point of the torque arm. Still not sure how % of rise, AKA %anti-squat, is calculated since the control arms contribute too.

My RLB's are done. I made them from scratch, and made 3 adjustment holes (4 counting the original). Each hole is 1" apart.

For anyone considering making these: they are very simple, but It required a lot of time to make these (specifically the placement of the holes etc.) If the holes aren't placed right, the car can "dog track", which would screw up the alignment and everything. IMO, For $65, the Spohn RLB's are definitely worth it.


------------------
87 IROC 350, 3:42 Torsen, pocket ported 083 heads, complete Edelbrock exhaust, Most free mods, Most little mods, aluminum d/s. Edelbrock STB, SSM sfc's, boxed rear suspension pieces, urethane bushings everywhere.
Stock cam, chip, runners, base, and trans
13.94@103mph, 2.25 60'
In the works: ported SLP runners, ported base, Xtreme Cam, homemade suspension pieces, and 27x10 Hoosiers.
Goal: 12.999

 

Wow this really turned into a big post, I would like to know do they help handling? should i get them? thanks alot

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86Z28, GM 350, Jet perf Q-jet & chip Dual snorkel air cleaner, Edelbrock performer intake, Edelbrock headers, Edelbrock cat-back, Off road pipe, MSD 6AL, Accel Super Coil, Taylor Spiro-pro wires, Rapid fire plugs, Jet fan switch, World class t-5, Hurst Short Throw Shifter, Ram Flywheel, Center force dual friction clutch,Aluminum drive shaft, BW disc rear 3.45's & a posi, PBR calipers, Earls braided brake lines, Polygrapite bushings all the way around, poly tranny mount & torque arm mount, Hotchkis lower control arms & panhard rod, Rancho limiter straps, KYB struts & shocks, Gm Wonderbar, Edelbrock strut tower brace, SSM sub frame connectors, Jamex lowering springs, Carbon metallic brake pads, Crossed drilled rotors, Mobil 1 Tranny fluid & motor oil, GM syntheic rear end oil, K&N, Grant stering wheel, 1,200 watt system, Jet Black Paint, 91 Z28 rims, 92 wing, Tinted windows.

 

This is a great post. Lots of useful information. Thanks. I'm looking for some suggestions, ideas, etc. to help me with the T-Arm suspension I am installing in my '57 Chevy car. I got a wrecked '95 Trans-Am that's donating the LT1/6 spd. and I decided to swap the rear end and retain the t.arm suspension.

This car will likely never see a drag strip and will probably never be driven really hard, but I would like it to corner reasonably well. I have already made my torque arm, and was trying to determine the frame mounting height for the lca's when I ran across this board. After reading some of the posts, I may end up re-doing my torque arm as it is about 10 inches longer than the original fbody arm(don't think I'll have any brake-hop problems). Course the 57 is alot longer(14"-15" at wheelbase) than an fbody and I have no idea how the weight distributions differ, but I may have to go shorter. I used the stock, rear of transmission, mount location and built it using 1-1/4"x.120 wall tubing top and bottom and 3/16" plate running full length in between. I feel like it should be strong enough, but if it is too long, I may have too much squat on acceleration. Again, I'm not drag racing but I would like to come out of the curves reasonably well(not like a 57 Chevy), but I suppose a small amount of squat would be acceptable.

To figure out the frame mounting location for the lca's, I made a full scale operational model on a piece of plywood with all of the dimensions taken from the car. I can change the mounting locations and then see how it affects the arc from full droop to full bump.

I think that the stock fbody lca's are mounted about 4-5 deg. front down with the car on level ground. I set the model up with 4-1/2 deg. and here's what I got: wheel moves forward over an inch at 4" of bump, and wheel moves rearward about 1/8" at 4" of droop. It's easy to see how to get a live axle to steer. I then set the lca level, and as to be expected, the wheel moves forward about an equal amount for both full bump and full droop.

After all of this run off at the mouth(or fingers), here are some of my questions and concerns: everybody's thoughts will be greatly appreciated.

Does the stock lca location create "too much" understeer?
Do you think the Torque Arm is too long"
Do you think that mounting the lca's level would counteract some of the ill effects of the long t.arm without inducing too much oversteer?
Anybody know how much suspension travel a stock fbody rear has?

 

So if hte front of the control arm is lower then teh rear. That will cause oversteer...what if you do want oversteer? Will the drop w/o the relocater help with oversteer?

 

If the front of the lca is lower than the rear this will cause the axle to steer into the turn which will cause understeer. At least that is my understanding. It will cause the outside wheel to move forward and the inside wheel to move rearward. Of course the amount of steering effect will depend on the amount of lca angle and the amount of suspension travel, among other factors. A stiff suspension that allows little wheel movement up and down will have less steering effect than a softer suspension that allows for more suspension travel through it's arc. Most of the axle movement fore and aft occurs in the second half of the suspensions' travel, again depending on the angle of the lca's.

 

Hey Tom,
Did you see the recent NASCAR race at Watkins Glen? Ther rear brake issue was illustrated nicely when Dale Earnhardt Jr. approached one of the turns. He got on the brakes too hard, got some rear end hop and as a result the rear wheels locked up. He then went spinning off the track into the gravel trap.

My car is lowered with Jamex springs and I can tell you that the RLB's made an improvement. The LCA's sit parallel to the ground and traction improved. I'm also running Steve Spohn adjustable LCA's, adjustable panhard bar and adjustable torque arm. I plan to add and adjuster bracket for the panhard bar that will allow me to change the roll center of the car.

I think IrocStan is in for a challenge in trying to set up a car that runs strong at the 1/4 mile and also runs strong in the corners. Both types of racing have different suspension requirements to be really good. You can get a car that runs okay at both, but personally I feel if you want to be really strong you need to focus on one style.

 

How about those who have been waiting for WEEKS for an answer as to if and when u will have these available for those who want to purchase them???

 

did you happen to notice the date of karls post in this thread, it is almost 2 years old.

some of us have been waiting for years to get these. just be patient for a couple more weeks, we are on the home streatch of getting these.