OK guys, we have been discussing rear control arms and the types of bushings to use for the most benficial results. It seems my recommendation may not be the best. Not the worst but not the best. Read through the results and judge for yourselves.....


While bind is only one of many parameters determining the handling characteristics of a suspension system, it is useful information, and has been a subject of great debate on these message boards. As part of the research we did in developing our rear suspension system, MM has actually done quite a bit of roll-bind testing. I can offer some hard numbers for everyone to consider. I will define ‘bind’ to be any resistance to wheel movement in a roll situation that is not from the spring or sway bar.
Let me say that this information is not intended to be negative toward any particular system, but should be used to gain understanding of the way cars with different setups feel/handle. This information can help everyone to optimize whatever setup they may have.
Of the tests we have done, following are the tests relating to the rear suspension systems most often discussed. All tests are with the sway bar disconnected, cycling one wheel through 3” bump/droop as if in a roll situation. The results are organized in order from least bind to the most bind.

1) 4 Link - LCA with spherical bearings or rod ends at both ends / Stock UCA’s
6lb/in Linear
This shows the stock upper arms introduce 6 lb/in of wheel rate.

2) 4 Link – MM LCA 3 piece poly, spherical bearing / Stock UCAs
9lb/in Linear
This shows an additional 3 lb/in resistance from our 3 piece urethane compared to a rod end.

4) 4 Link – Stock LCA / Stock UCAs
11lb/in Linear
This shows that the stock LCA adds 5 lb/in of wheel rate, which is actually more than our LCA of case 2.

6) 4 Link – LCA with 3 Piece Urethane at both ends / Stock UCAs
26lb/in Linear
Case 6 shows that the 3 piece poly (or any LCA) works best with a spherical bearing at one end. 17lb/in is added over case 2. Note that the effect of adding a 3 piece urethane at only one end adds 3lb/in. Add it at BOTH ends and the increase is 17lb/in… NOT 6 lb/in as one might expect.

7) 4 Link - LCA with delrin, spherical bearing / Stock UCAs
30lb/in Linear
This shows that delrin does not allow necessary angular deflection resulting in an additional 21lb/in over case 2.

8) 4 Link With PB - Stock LCA / Stock UCA
In the first 1” travel 47lb/in
Between 2-3” of travel 30lb/in Decreasing Rate
In case 8 & 9 the Panhard bar defining a new lower roll center is forcing control arms to travel a new path of higher resistance.

9) 4 Link With PB – MM LCA / Stock UCA
In the first 1” travel 50lb/in
Between 2-3” of travel 30lb/in Decreasing Rate

10) 4 Link – Stock LCA / UCA with rod end at chassis, stock rubber at axle
In the first 1” travel 63lb/in
Between 1-2” travel 39lb/in
Between 2-3” travel 20lb/in Decreasing Rate
Case 10 represents trying to locate the axle with a stiffer bushing configuration on the upper control arms. Since the upper arms need to have an effective length change, the rod end in this case actually creates MORE bind.

11) 4 Link – LCA with urethane at both ends / Stock UCA’s
67lb/in Linear
Case 11 is similar to case 6, but shows that a standard poly/poly control arm does not allow much angular change.
OMG :eek: :eek: did you guys running poly arms see test 11. That is 6X the amount of bind that OE arms have.

Obviously the best set-up is going to be stock but rebuilt upper arms with tubular spherical bearing lowers. Guess that officially ends the debate.

Attesting to that poly/poly set up, I have this on my 70 at the moment. Very stiff in back, hits bumps and ruts like a Mack truck. I hate it, going to Edelbrock or something similar very soon. I have poor traction on the street and the track, this has something to do with it I am sure.

Also, with a rear sway bar attatched, this will change the bind/free movement ratings? I see this test was a one wheel only lift and not rated for straight up and down movement and without a sway bar (like the bind I am experiencing) I would imagine this would be specific to an uneven road surface or would this benifit a good all around suspension including up and down free movement?

Dennis-good post, it says it all!!
This is what Global West recommends except that their LCA's only have one spherical end.
Cheers
Steve

That's great info if I was running circle track or a road course with the Chevelle but how does this all apply to us drag racers? My suspension consists of NO conventional sway bars (only rear anti roll) and I'm looking for weight transfer only. As long as the pivot points of the control arms are loose and the arms are allowed to move up and down in their designed path, why would it matter what the bushings are made of?
Just call me dense because I've read it twice and still don't understand how it applies in my application. :confused:

suspension design does not care what you are doing with the car. For it to work to properly you cannot have a "binding" rear suspension.

The term for the reaction you desire is "anti-squat". AS is determined by the side-veiw-swing-arm length (the imaginary lines where the upper arms and lower arms would meet). The shorter the SVSA the more AS you will have. Raising the axle mount of the upper arm or frame mount of the lower arm (not really possible) OR lowering the frame mount of the upper arm or the axle mount of the lower arm will accomplish this.

Adding bind to the system to make it "feel" tighter does not mean it works better, you just perceive that it does because nothing is moving. You would have a much better suspension if it were designed kinematically free of bind and moved the mounting points around to suit your needs.

Craig, in a word-yes. lifting only one wheel is the best way to test for bind/articulation. The more free the system the better it can work.

The question "What rear arms are the best" is only relative to the application.

No Chris, it's not. For everybody else who hasn't been paying attention......binding suspension does not work well in ANY application regardless of what you are doing. Go check out some Top Fuel or Pro-Stock cars. see how much bind they run. I can tell you right now the answer is as little as possible. The correct way to increase AS is with design not bind.

Why does it seem those who run poly bushings seem to insist this tech that has been accepted by many of the top engineers in the world is inconclusive? In fact it has not refuted 1 single time. Is it a little bit of denial maybe...we spent a bunch of money on junk because advertising say's it's the best?

So Dennis, Does test #10 simulate the Currie/Edelbrock uppers?

Interesting... I know they will still "bind" even with the sperical "Johnny Joint"

I'd like to see Currie uppers with RUBBER in the axle housing...


I think this leads back to a comment I made several months ago (and you gave me a bad time Denny!). I mentioned that the upper arms were "designed" to flex... Maybe they weren't actually "designed" that way, but I think that flexing (in addition to the rubber bushings) is what reduces the bind... I wonder if that is a reason that GM didn't use stiffer upper arms? It was a compromised system from the start...


So now to decide if I want the Currie uppers, or stay with my rebuilt stock uppers??? I already have the GW spherical lowers...


I know with stock uppers with poly bushings, it was very hard to get the rear springs in place (the rear would barely drop enough), and very hard to hook up the rear shocks, as the bind made it hard to get the rearend up high enough to bolt the shocks on... I could put all my weight (250+) onto my 1/4 and only move about 1/4" or so... it was so stiff, it would "skip" around corners with small bumps in the road. Now with only the change to rubber upper bushings and GW lower arms (same springs and shocks). Much nicer ride and road feel now...

Great info Denny...

Now I'd like to see that kind of comparison between the stock 4-link and the HTH Truck Arm...

Why does it seem those who run poly bushings seem to insist this tech that has been accepted by many of the top engineers in the world is inconclusive? In fact it has not refuted 1 single time. Is it a little bit of denial maybe...we spent a bunch of money on junk because advertising say's it's the best? Denny, for a drag car with sticky tires, the Poly/Poly MIGHT work well, as it will reduce the squat even further and possibly "planting" the tires harder...

But yeah, for handling, its not the ticket...

Aren't you redesining you rear suspension? Tell us more...

I run stock,but new rubber bushings and the F41 suspension.No special shocks either.
Nice and simple

Originally posted by dennis68:
Obviously the best set-up is going to be stock but rebuilt upper arms with tubular spherical bearing lowers. Guess that officially ends the debate. Dennis who is MM? So what about SSM bars, how do they rate on the scale?

Thanks graemlins/thumbsup.gif

Yeah Tony, I am building a 3-link. The same guy who did this study also analyzed T/A arrangments, they placed #3 and #5. I would imagine truck-arm arrangements would likely be the same. Possible improvements if you went with the uni-ball arm instead of the rubber bushed arm.

If you wanted to run poly to reduce squat why noy just run solid links for shocks? Same principle.

I think this leads back to a comment I made several months ago (and you gave me a bad time Denny!). I mentioned that the upper arms were "designed" to flex... Maybe they weren't actually "designed" that way, but I think that flexing (in addition to the rubber bushings) is what reduces the bind... I wonder if that is a reason that GM didn't use stiffer upper arms? It was a compromised system from the start... Yes, even I make mistakes....mark your calanders. I doubt GM engineering designed the arms to flex and allow for articulation. I think it was an interseting side affect that worked out for the best. Anything is possible though.

Dennis who is MM? So what about SSM bars, how do they rate on the scale? MM is Maximum Motorsports. They are racing team/engineering fabricator that caters to the Mustang crowd. Fortunatly we share the same suspension design so their R&D can be applied to "A" and "G" bodies.

SSM runs poly so they will rate about the same. They do relocate the arms slightly to improve AS which is good. The geomtry improvements improve the grip, not the bushings. It's a trade-off. If I were only concerned with straight line driving and couldn't/didn't want to do any fab work I would probably run them.

Think i'm going to try the new UMI adj. uppers and use the stock rubber in the rear, just to get the pinion angle correct. does anyone make an adjustable upper with the rear hole lower to also help the roll center? Ralph

Okay, then let me ask the stupid question: many of these set-ups add higher bind rates which equates to roll stiffness, does it not? Greater roll stiffness is like adding a larger anti-sway bar isn't it? (Not that that is what you want, just what it does.)

All other components being equal, what is the difference between a rear suspension with a high bind rate and softer springs vs. a rear suspension with low bind rate and stiffer springs? Both could have relatively equal amounts of overall roll resistance, it's just that each system is accomplishing it in different ways. Within reason, why does it matter how you get there (aside from the obvious bad effects of added stress on mounting points if you add too much bind)?

Again, I'm not saying adding bind is the preferred method to add roll stiffness, just trying make a point that there are more factors involved than JUST bind (as Mr. MM states in his info). It would seem what matters most is chosing components that compliment one another instead of excentuating their weaknesses while working within you budget and mechanical skills.

Rich,
the problem is that the Binding is much greater than needed... Its almost too stiff... The same thing could happen with "too stiff" springs, but probably stifferthan whats readily available.

If ultimate roll stiffness were better, then racecars would have solid suspensions... But since roads (and racetracks) do not have perfectly smooth surfaces, the suspensions do need to move or articulate to adsorb those bumps...

Not entirely the same, but think of an empty pickup truck... The back end is often almost too stiff for good handling/cornering (I think this is also why a "performance" truck like the Lightning doesn't have the payload capacity, due to softer springs)... it will tend to bounce/skip around rather than have the suspension adsorb the bumps. When the suspension adsorbs the bumps, the tires remain in contact with the pavement...


Also, the springs will adsorb some of the energy. With the suspension in such severe bind, that energy will go elsewhere (possibly cracking control arms or the frame crossmember, especially on a 40-year-old frame).

The sway bar/anti-roll-bar does not necessarily increase the roll stiffness. It basically ties both sides together. So if both wheels hit a bump, etc the swaybar does nothing.

By the way, really big sway bars, especially on the rear can and will often cause excessive oversteer also...

There also snap-oversteer that we haven't touched on yet. That is by far about the worst condition imaginable and inherent to overly bound up suspension.

Originally posted by 1966_L78:

The sway bar/anti-roll-bar does not necessarily increase the roll stiffness. It basically ties both sides together. So if both wheels hit a bump, etc the swaybar does nothing.
Sure it does. If both wheels hit the same bump at the same time, the sway bar does nothing I agree, but if the car is in cornering mode with the body wanting to lean to the outside, the sway bar transfers some of the outside suspension compression to the bar and to the opposite, inside suspension thus effectively increasing roll stiffness. The same is true if one wheel encounters a bump or hole while the opposite side does not.

Regardless of whether a sway bar is the best method to accomplish it, they do increase roll stiffness. Unless I'm using the term roll stiffness incorrectly. I am referring mostly to the amount the body will roll to the outside in a corning situation. Maybe a better way to put it is: Anit-sway bars add roll stiffness when the input to the suspensions on each side is not equal.

That test confirms what Global West says about their products. GW is one of a very limited number of performance manufacturers that actually EXPLAIN how their product works. The fact that they also offer poly in their control arms proves just how little your average consumer knows about this subject.

I'd like to see the test expanded to include the graphite impregnated poly bushings and the poly bushings with lube fittings. It's no surprise that the spherical end bearings win hands down but how do they compare when cost and durability is a factor?

Rich, you want to increase roll stiffness to a point but not by introducing bind. Bind leads to a bunch of different issues including unpredictability and possible loss of control due to extreme changes in chassis attitude during roll.

Steve, lubed poly or poly graphite wouldn't make any difference as the bind issue is from lack of compliance not freedom of rotation. Bearings/links are actually cheaper than poly bushed links if you know where to shop. How long will they last, most dual purpose cars are getting 2-3 seasons out of the bearings? How long do rubber bushings last, I change them with less than 3 years all day.

SSM runs poly so they will rate about the same. They do relocate the arms slightly to improve AS which is good. The geomtry improvements improve the grip, not the bushings. It's a trade-off. If I were only concerned with straight line driving and couldn't/didn't want to do any fab work I would probably run them. [/QB]Do we have a way to load pic.s on here?My SSM lift bars and upper control arms have steel bushings.The only place that takes traditional style bushing is the 2 center ones on top of the third member.Did SSM make a different set up than mine?I also heard they went under,I've seen Lakewood and Jegs with what look to be the same set up.Did they get bought out?

Damn good info, confirms in hard numbers what my "butt" g-meter has told me for years after playing with different arm / bushing configurations.

Unfortunately for those of us needing some measure of adjusting pinion angle, we're sort of screwed when it comes to UCA choices. I'm running the Edelbrock uppers now with rubber at the rear end, and while very smooth, it isn't quite as smooth as it was with the stock UCA's with rubber at both ends. Still a very predictable and stable setup for the stock C4L, but not quite as smooth as the stock UCA's with rubber on both sides, and leaps and bounds away from 4 boxed arms with full poly bushings.

I did not see any testing of fully boxed LCA/UCA's with full poly bushings, I would have loved to see that result. Heck, test 11 (polys in the lower only) added nearly another 50% of the typical rear spring rate on these cars! :eek:

I'm not surprised to see the stock UCA/LCA combo having such a low resistance. With stock rubber in the LCA and UCA I noticed that the resistance to movement increased quite a bit as you moved farther away from static loading height, as the bushings are forced to twist internally more and more; i.e. they moved quite freely near ride height but became stiffer and stiffer as you moved farther away in travel as the bushings "wound up" more. Tighten those rubber bushings while not at ride height, and expect some unusual behavior. I would expect greatly increasing resistance once you start moving past the 3" of travel used in the test; but if you're seeing that much travel you're probably well outside the realms of the "handling" area; i.e. going up and over a curb, a pothole, etc.

Once again, this also confirms what I've said all along in several posts like this-- the factory knew what they were doing when they designed these suspensions, and made a pretty good low bind setup on the cheap with stamped arms and rubber bushings. Unfortunately the slight lateral "squirm" under hard cornering with the all-stock rear is a bit unnerving for those of us slinging our cars hard through turns.

Troy

Once again, this also confirms what I've said all along in several posts like this-- the factory knew what they were doing when they designed these suspensions, and made a pretty good low bind setup on the cheap with stamped arms and rubber bushings. Well... I wouldn't go that far. There is quite a bit of improvement to be had by simply switching to lower links with rod ends. The C4L is actually one of the worst designs ever, maybe beat out of the top worst ever designs only by the Hotchkis design (leafs).

There is also the whole "this design kinda sucks so it could be drastically improved with just about anything else" theory.

LOL Denny, you're right. I forgot to stipulate the factory did a fairly good job considering their packaging and cost constraints. There are definately far better designs out there, but in all the factory job isn't too bad when taken in context of the original design parameters. Remember, they weren't out to design a road racer!

All I'm saying is that given the space allowed, budget constraints, and design goals (which was probably just a smooth riding rear end for their midsize sedan) I would say the General did a pretty good job.

Room for improvement? You bet!

Troy

Agreed!

I'm figuring I can stuff a 3-link into my car by raising the tranny tunnel around the back seat, making a new crossmember, and switching to Camaro/Firebird buckets in the back. I hardly stuff anyone in the back anyways, what do I care? :D

Just gotta find a way to snake tailpipes around a PHB. I don't want undercar or before the rear tire exhaust dump...

Troy

What about the truck-arm kit? Is it worth the money? I'm sure it's a huge improvement, but probably not worth the price...

The HTH truck-arm kit is an improvement. There are better systems available but require YOU to design and fabricate them. The guys at HTH have done the R&D; all you have to do is some cutting and welding.

My thoughts are if you capable to cut and weld a truck-arm kit in then you should be able to the same with a parallel 4-link or 3-link as well.

Good tech info. I`ll toss in a few more observations. The rear swaybar does effect bind on the A and G chassis to an extent. Being fastened to the splayed LCAs directly it`s not a pure torsion bar but also has to bend. For that matter the ends need to bend in order for the rear to move laterally so it`s got a (small) hand in that as well. A seperate 2nd/3rd gen Camaro type bar would be a BIG improvement. We`ve been playing with a few prototypes and getting encouraging results. What`s more since the LCAs effectively become the levers acting on the swaybar`s torsion bar segment and they`re roughly twice as long as the bar`s own arms the rate of the rear bar in it`s factory configuration is FAR less than figures on the unmounted bar would be. As a result these cars in general need to run larger dia. rear bars (and or smaller front ones) to attain neutral handling.
Back to the bushings. We`ve had a couple cars come into the shop with 4 fully boxed arms with poly bushings and all exhibited a *very disturbing* tendency for snap oversteer. I don`t mean just a little either,I`m talking half a turn of counter steer here under the right (wrong?) conditions. Swapping Edelbrock UCAs with spherical bearings on the frame side only was enough in all cases to eliminate the scary snap oversteer at least as far as limited testing on public roads and on street tires could determine. I`m almost certain that it would rear it`s ugly head again if testing was pushed a little farther though. Rubber or spherical ends on at least one side of each arms would probably make a considerable improvement. Dennis`s info would seem to bear this out. Marcus

Awesome, have some very good info in this thread on our rear suspensions. Keep it going :cool:

Originally posted by dennis68:
My thoughts are if you capable to cut and weld a truck-arm kit in then you should be able to the same with a parallel 4-link or 3-link as well. I'm definitely capable of fabrication, my problem is a very limited knowledge of suspension technology, so designing my own setup and having it work properly on the first try probably wouldn't happen. Also, I don't want to have to modify the floors of my car... if I tear in that deep, I'll never get done.

Unless there is an affordable alternative, I guess I'll be keeping the C4L setup and running spherical ends. The HTH kit is just not within my budget. Any fabrication I can do to optimize this setup would be doable.

Derek, go buy Herb Adam's book "Chassis Engineering" and Steve Smiths book "Paved stock car technology". Read them both cover to cover 3 times. Wait 1 week for the information to be properly ingested, then go into the garage and do what need sto be done.

So where do ladder bars fit in here? From what I understand, they bind up the suspension pretty good, but provide good results for straight line traction. So, in this case, how similar would that compare to, say, using all poly bushings with boxed upper and lower arms? This would bind it up too, so would there be some benifit to straight line action with ploy busings? Or does the ladder bar's forward mounting point have more to do with why it helps while going straight?

FWIW, I have SSM's, and I used to use Hotchkiss poly uppers. I switched to edelbrocks, and I immediately noticed a change in ride and handling. Much less bouncy and jarring on bumps... doesn't seem to skitter over a bump on a curve like it used to.... which is good! smile.gif

chris

No comments dennis68? I was hoping to hear what you thought about ladder bars vs. binding poly suspensions for straight line action. (and possibly ladder bars for cornering too)

Please don't tell me I killed another thread.... :( I thought that only happened when I posted in bench racing! smile.gif

chris

Ladder bars do not corner at all, you haven't killed the thread.

I'll do my best as I am not terribly fluent in ladder bar arrangements. The ladder bar firmly mounts the top and bottom of the axle to a single bar which has a fixed pivot location. This is nice for drag racing as it limits pinion climb and forces the all the power to the gears set.

The draw back is that having the axle solidly mounted in such a manner removes the axle’s ability to articulate freely through its range of motion, what ever that might be. Although this system would be free of bind in a drag strip application, kinematics says it doesn't work at all. As soon as you started to roll the axle would attempt to twist as the bars cannot move independently of each other.

I may have confused this even further...if so I apologize, I haven't done any practical application of this system so I can explain how should work in theory.

who makes the LCA's in test 1??

UMI is in the process or you could make your own with PHB materials. If there is enough interest I'll see what it would cost me to have a bunch made up.

whoops, sorry.

so whats a dumb ass like me to do now? i installed BMR lower control arms with poly bushings. should i just sell the uppers i have not installed yet? i planned on running lowers as installed with the adjustable uppers with poly installed in the bar and the pumpkin. also have the the hotchkiss bars to triangulate the rear. car is NOT a corner carver and only interested in straightline acceleration. maybe just run rubber in the rear? thanx mike

hey guys, My 71 chevelle has a negected rear end in it, the car jumps all over the road and it has bad wheel hop (it does have an aftermarket rear sway bar). I've got to fix it. I'm 18 and dont want to spend anymore than I have to. Just by reading on this forum and thinking about the design of my rear end, it sounds like I should get some lowers with spherical bearings or rod ends. Where could I get the best deal for a set? Could I buy the spherical bearings or rod ends seprate and fab my own arms? If I could do that would it be real easy to build them incorrectly? I have the tools and some experience with metal work. Thanks!

If your ONLY concern is how quick it runs the 1320, then go ahaead and run the poly stuff. It will decrease your 60ft times as running all poly will act similiar to a ladder bar arrangment by locking the axle rotation up. Your call.

what about those braces that go on the two frame mounts?what do they do for cornering?

Not a lot, they are more to reinforce that crucial area.

Nice write up dennis, glad to see some real tech influenced by real testing making its way over here. I was suprised on the "johnny joint" application. How do you think those poly reinforced johnnys would do if it was rubber instead, but with the delrin inserts like the new Hotchkis ones to take on the point loads.

Based on what I have seen so far with regards to the test results, anything with Delrin or Teflon is going to increase bind to the x^.

I had originaly thought as did many that if the system was free in theory, like in the case of rod ends, that overall system bind would be nill. Testing has shown that it is essential for the upper links to not only be constructed of a maleable material, like stamped steel instead of square stock or tube and have bushings that are easily manipulated.

In short, I think the results would only get worse with Teflon type bushing but might work OK with a rubberized version of a johnny joint.

Ok let me get this straight are you guys saying the new UMI Adj. uppers will hinder more than help? Should i just get a set and use rubber in the pumpkin? Or should i buy a solid set that changes the bolt location in the rear for a better launch angle? Ralph

Dennis those tests do pose some problems with the stockcar thinking. Everyone uses heims at every end they can and if i read this right the tests say thats not the way to go?!?!?! Your losing me here i've never seen a more "free" rearend than a total heim mounted one. Ralph

Originally posted by mason71:
Just by reading on this forum and thinking about the design of my rear end, it sounds like I should get some lowers with spherical bearings or rod ends. Where could I get the best deal for a set? Mason, Denny is working a deal for us with UMI Performance right now. Why not see how that turns out. Check their web site (www.umiperformance.com). Their prices are pretty darn good even without a deal. I would wait and see what their new lowers with spherical joints (about to be released in a week or so, according to them) sell for. That's what a bunch of us are doing.

I'm not trying to shill for anybody but based upon what they already sell, their pricing, and the discussions I've had with them, I think they are a potentially excellent provider of these parts. All we can do is wait and see. They have a larger market to satify and capture for business purposes than us. It would be great to have solid provider of these rear suspension parts that actually understands "OUR" machines and challenges. From the number of "full poly bushing" arms being offered for these C4L designs, I'm not convinced some vendors do, or care about anything but marketing hype to get your $$$. But then, that's what this forum is for, isn't it? To debunk the myths.

Just my $.02 worth graemlins/thumbsup.gif

Originally posted by Ralph67:
Dennis those tests do pose some problems with the stockcar thinking. Everyone uses heims at every end they can and if i read this right the tests say thats not the way to go?!?!?! Your losing me here i've never seen a more "free" rearend than a total heim mounted one. Ralph Stock cars do not use C4L suspension for the most part, they have been using truck arms for at least 20 years. Some of the smaller series use them only as a means of controlling costs by limiting modifications.

Heims in theory pose not bind issues until you consider the complex working angles of the C4L.

Just to clarify, "hooking up" for track use and daily drivers/corner carvers are totaly different beasts. Some of theroy still applies but it is virtually impossible to do both well without major design changes which is not the intent of this thread....we can start another one to discuss the advantages/trade-offs of the other designs if ya'll want.

Your losing me here i've never seen a more "free" rearend than a total heim mounted one Ralph,

I think the main problem is that arms like the Currie/Edelbrocks only have the heim at one end They allow the arms to swivel off the frame, but really the arm needs to go into an "S" shape to be free off bind when the suspension moves. The factory stamped steel arms are flimsy enough to flex (and the rubber bushings help)... And none of those tests were with heims at both ends of the upper).

The main problem lies in the arms themselves... When they are too stiff (boxed aftermarket), they do not flex, and the bind is more severe.

This is mainly the upper arms, because they are placed at radically different angles, relative to each other, and swing through different arcs...

The lower arms are almost parallel, and as such, the binding is not as severe, and the single swivel works pretty good...

Denny/Troy, what about using upper arms with heims at both ends... Would that would help (no elongation, but flexibility and adjustability of the pinion angle... I am thinking for ride/handling as opposed to pure launch...


If anyone ever has a chance to SEE a Chevelle rearend out of the car (especially with the upper arms in place), rotate both upper arms and you can easily see why the system binds. If you move the arms, they want to move the "frame" mounting points together. But when installed, the frame prevents the mounting location from moving... Somethings got to give, and in stock form, its the arms flexing...


All I'm saying is that given the space allowed, budget constraints, and design goals (which was probably just a smooth riding rear end for their midsize sedan) I would say the General did a pretty good job. I find it really amazing that Ford used a similar design for the Fox Mustang, years later... I'd have thought they would have wanted to design a better handling setup...

Originally posted by 1966_L78:
[QUOTE] ]I find it really amazing that Ford used a similar design for the Fox Mustang, years later... I'd have thought they would have wanted to design a better handling setup... Check the new Mustang...they fixed that little oversight this time.

Alright i see what you mean your talking strictly 4 link (sorry). I was referring to a 3 link stockcar style. So should i try the UMI adj. uppers with rubber in the pig or just use something to adj. for instant center on the top? I also have the lakewood style traction bars on the car. I guess i shouldn't confuse the stockcar stuff i'm used to with the 4 link. Ralph

The UMI's would work OK for pinion adjustment on a straight line car. Properly set up you shouldn't need the no-hop bars.

so... what you're saying is, stock uppers with rubber bushings, and tubular lowers with johnny joints is ultimately the best handling suspension achievable on a chevelle chassis without fabrication, correct?

Correct. graemlins/thumbsup.gif

You're my hero :D

Hey, thanks for the reply Herb!! graemlins/thumbsup.gif

A comment regarding the ladder bars back a few...

These could be very good for the 1/4 and very bad for corners. They should change AS for the better and work like a *very* strong anti-roll bar (they turn the axle housing into an anti-roll bar). For drag this will help equalize the natural lifting of the right side tire since it prevents almost all roll.

But again the overly strong anti-roll bar would make for an oversteering pig in the corners.

Hi Steve- graemlins/waving.gif

Denny, et al,

Let's touch on Sway bars for the new agreed upon C4L config. Sounds like a 1 inch rear may be too stiff for weekend cruiser. And, 1.25 might be a little too stiff for the front with stock rubber C/A bushings. If I want a good ride and handling but don't need a corner carver, what are we talking now, 1 inch front and 7/8 rear?? Looks like my stock front is 7/8 and I don't have a rear bar right now.

Little by little I'm getting the right brake and suspension config for this 67 figured out based on the help from all you guys. Thanks.

So far I've settled on:
11 front power disks
rubber bushings in front
Possible raised pivot point upper ball joints.
Boxed lower front C/A ball joints- a la Pete Lohr.
Spherical joint UMI lowers in rear
Stock upper rears with rubber bushings

Need sway bar recommendations.

BTW, this is a PS car with a quick ratio box and a 400 SB, 4 speed, 10inch open rear (right now)

What am I missing. Hope to have the frame back from the galvanizer by end of Feb. so I'm starting to assemble these parts now.

Global West recommends a 1 1/2" front sway bar for BB and 1 1/4" for SB, none in the rear for what they call "performance street driving".I was kind of suspicious of their recommendations, not knowing if it was just "fluff" to sell their products or not. Now I tend to pay some heed to their recommendations since their suggestion for rear suspensions is to use the stock upper control arms with rubber bushings and their lowers with a spherical end, exactly what was arrived at in this thread!!
Cheers
Steve

Herb, PM sent.

so... what you're saying is, stock uppers with rubber bushings, and tubular lowers with johnny joints is ultimately the best handling suspension achievable on a chevelle chassis without fabrication, correct? Originally posted by dennis68:
Correct. graemlins/thumbsup.gif So I'm done...


Honestly though, whats the best way to go IF the pinion angle needs adjusting?

I modified my trans crossmember to drop the trans slightly (which changed the angle slightly), but have yet to check the angles (just need time to do it)...

Would it be better to go Currie/Edelbrock with rubber housing bushings, or somehow fab some upper arms with heims at both ends (not sure how that can really be done without ALOT of work)?

Actually, I'd like to get a Johnny Joint that could be retrofitted into the front of the stock upper arm, in place of the front bushing...

Fabbing arms with bearings at both ends is easy...the problem is that would introduce a whole new kineamatics issue. Although releiving the sytem of bind it would force pinion angle change at a drastic rate during roll and force the axle to act in a sense as sta-bar.

Bind is bad but not the only thing to consider when dealing with suspension design, there are many other factors to be considered and foundation kineamatics is as important as any other function.

So if the adjustable upper LCA's (Currie and Edelbrock)are one of the worst binding culprits, what can be used to adjust the pinion angle other than raising/dropping the transmission mount or crossmember? Dennis, I'm in on the UMI Performance LCA deal if you can make it happen.

How about determing the amount of change you need and how much shorter/longer the arm needs to be, then finding a donor car with that length arm. Older "A" bodies have shorter arms and Mustangs use a shorter arm I believe as well.

Just had to do this.

I thought that the pinion angle had to be changed at the rearend not the tranny end. By dropping the tranny you will change drive shaft angle but not the actual angle of the pinion. Ralph

It's a combination of both.

"Google" pinion angle and you will get quite a few "good" sites that can clearly illustrate what is going on and how to correct it if it's wrong.

Would it be possible to make adjustable lowers for setting the pinion angle, or would that cause other problems. Obviously, it would be very critical to adjust both exactly the same, but other than that, would it work?

Yes, it would adjust pinion but would require much more movement to gain any angle. It would also change wheelbase and may cause tire to fender clearence issues.

SSM bars allow pinion angle changes with stock uppers. It didn't seem to affect the wheelbase by any noticeable amount for me. I don't see how it would be any worse than adjustable uppers. The only difference would be that to gain pinion angle, you would be moving the rear back, rather than ahead.

I would think the main concern would be "dog tracking" caused by not having both adjusted exactly the same.

Another concern might be that under accelleration, the lower bars have compression forces exerted on them, while uppers have tension. You would probably have to build them much heavier to keep them from bending. (think pushing a rope... the rope is very strong for tension, but has almost no compression capability).

Good to know Derek, most arms put the pinion adjustment on the top which means either poly or bearings at the ends....now if somebody build an adjustable tube link with rubber bushings, that may be worth experimenting with.

I`ve done quite a bit of experimenting and road testing with the C4L configuration also. My findings are slightly different but I stress binding caused by chassis lean rather than straight rebound travel. I`ve used the Edelbrock arms with the spherical bearing on several cars and tested them in my benchtop rig. I think they`re (and Currie`s too) one of the best alternatives for the admittedly compromise rich C4L suspension. I don`t particularly care for the poly bushings they use on the axle side and like to use high durometer rubber given the choice. I haven`t noticed a great deal of difference with either poly or rubber in the LCAs provided they`re stock U channel configuration (even factory boxed). The square tube LCAs have more binding issues which are compounded by poly bushings. I think the stock lCAS have enough torsional flex that they partially negate the effects of poly bushings. It should be pointed out that binding is an issue but is not the *only issue*. The UCAs are also responsible for the lateral location of the rear. In this respect the spherical bearings and higher durometer axle side bushings are an advantage over stock UCAs and stock rubber bushings. They give the car a more planted,more linear feel in the corners IMO. It`s all compromise,it`s just deciding where and how much of what... ;)

As for the rear swaybar I really disagree with that. There are a lot of variables involved here,especially when we start messing with spring rates and geometry. Until you know all of them you can`t even take a good guess at sway bar size and rates. GW bases many of their recomendations on their packages,their swaybar recomendations may work well with their spring rates but they`ll induce a great deal of understeer on an otherwise stock Chevelle. The recomendations above would be a good start for a typical 1st gen Camaro... A bodys have a LOT of understeer out of the box even with a factory rear bar. A 1" bar is not that much stiffer than the factory 7/8" bar because both are weaker than their dia. would suggest. The fact that they`re bolted as they are to the long LCAs reduces their rate to less than half of a typically mounted bar of the same length. A 1" rear bar on an otherwise stock A body reduces but won`t eliminate understeer and makes turn in much more lively. You`ll still need some power to induce oversteer. Marcus SC&C

The study performed was done in a manner consistent with roll, not bump/rebound sorry if I didn't make that clear.

Agreed that linear binding is the only measurement of how well a system works but second to basic kinematics it is the most important.

It is important to remember that even with a solidly planted rear if the links induce bind (especially if the amount is progressive as roll increases) then snap over steer becomes a very real danger.

I need to simplify this thread a bit so that I can figure out what I need to do with my Chevelle. I have a 72 Chevelle Malibu 4dr. I have a modified 12 bolt (c-clips have been eliminated by bearing retained axles). When the rear end was installed the two upper differential bushings were replaced. ALL of the remaining 6 RCA bushings are origional IE: 32 years old. I have noticed that off idle at light throttle there is a noticible rear end shimmy for a second. Has been there since I got the car three years ago. I have had the drive shaft rebuilt so u-joints aren't responsible. I have been thinking lately about "pinion angle" as the culprit and have been considering re-bushing the LCA and adding adjustable UCA's. This thread makes me doubt everything I have ever heard. Now I am wondering if I should just rebush all CA's with rubber. I also added a rear anti roll bar (1") which with the origional street tires caused the rear end to "jitter" around a hard corner with hard acceleration. I have since gone to 10" rears and 8" fronts and at present I have had no further "jittering" problems. The car will mildly oversteer as I had expected it to do. If anything it is now as close to "neutral steering as any car I have ever driven.

What to do?


Is "pinion angle" the likely problem due to worn bushings causing the little wiggle. Additionally I am noticing a nasty high speed vibration that seems to be at drive shaft speed that is occurring at lower speeds with the passage of time. Leading me to think that if my problem is caused by worn bushings then they are getting worse exponentially. Obviously I SHOULD get new bushings or do SOMETHING....I just want to know which way would be best.


My car is a daily driver that I love to crank around corners as quickly as I can. I love cornering just as much as I love speed.

Rebush the UCA and pick up a pair of boxed or tube LCA with spherical bearings or johnny joints at both ends.

After the bushings/links are done then take measurements for pinion/driveline angles. Make sure the rear is supported by the axle and NOT the frame. There are several pinion angle finders on the market to make it easier but a basic angle gauge will work.

Also check the mounts, a broken trans mount can cause pinion angle problems.

Different strokes Denny smile.gif ...I`ve experienced snap oversteer in A bodys and G bodys with bound up rear suspension (it`s no fun!). In these cases Edelbrock UCAs were the cure,not the cause (box tubing arms with poly bushings were). I did notice that the Edelbrock arm spherical bearings are VERY STIFF,out of the box. After a hundred or so street miles they break in and pivot very easily. Could that be responsible to the differences in our results? Have you ever tested them with rubber bushings on the axle side? That may be a better compromise? BTW did you test the LCAs with a rear swaybar mounted?

Charbilly,IMO replace the bushings with stock rubber,leave the stock arms alone and spend the difference on the best set of performance shocks you can afford. It`ll make a much larger difference in handling for your money. Marcus

No, I may run the Edlebrocks for testing. Rather than bench testing I am going to rebuild the rear stock and run some track events for baseline. I decided that although bench testing is a very useful tool for studying what "should" work, real world results speak for themselves.

I am going to run stock uppers/rod end lowers for sure. May experiment with Edlebrock uppers and possibly running the C4L with a PHB as well just to say what works and what doesn't.

If Adams is the king of soft spring/big bar I would be the king of heavy spring/no bar. I don't like using sta-bars as a means of determining roll stiffness, as a tuning tool OK. I don't run rear bars at all. I am sure they would increase all the bind numbers equally though.

Denny, my experience with the Edelbrock uppers was that switching from stock uppers with rubber front and rear to the Edelbrocks with rubber on the axle didn't change handling; however, my bad vibes from the pinion angle being wrong with the stock arms went away (my real motivation to switch to the Edelbrocks). The Edelbrocks do transmit a bit more NVH to the car because of the lack of isolation offered by the front johnny joint, but I didn't notice any ill effects in the handling.

I really want to try a set of Currie lower arms to see how they compare to my current Global West TBC-4's. Right now, with the springs out, the frame supported by jackstands, and a jack holding the rear end at standard ride height it is surprisingly easy and smooth working the rear end by hand simulating a roll condition. It's so easy to move that I don't see how much the Curries could improve things, but I'm always up for trying something new. However, rather than buy the Currie arms I figure I'll throw that money towards buying an Elky frame so I can build a 3-link on that.

Troy

Well shoot, if I bought the Edelbrock style upper arms, would it be (or can I) replace the axle side poly with a rubber bushing. Would this be the best all around compromise for the UCA?

I am going to give it try Craig...we'll see what happens. My guess is that it won't be as good as a stock arm but not as bad as heims at both ends.

Note:something I forgot to mention early on in the thread is that not only does the poly induce bind as a result of it's inability to allow "twist" in the arms but as the axle rolls the arms NEED to change length. Obviously a solid link cannot change length so the bushings give allows for some movement, this is why the bearings in all positions do not work.

I would guess that with the johnny joints in the front of the edle brook (inside joke) and rubber bushings at the axle there at least be some compromise.

Originally posted by dennis68:


I would guess that with the johnny joints in the front of the edle brook (inside joke) and rubber bushings at the axle there at least be some compromise. :D I think the guy wrote elder brock, was funny as hell. But the consistant revving was getting very annoying I must say. I think I speak for the rest of us here tongue.gif

So, using a rubber bushing on the axle side would be the best comprimise for length change and flexibility I will agree with. When the time comes, those arms will get some rubber in them, unless another member has done this with negative results.

Originally posted by THORSS70:
</font><blockquote>quote:</font><hr />Originally posted by dennis68:


I would guess that with the johnny joints in the front of the edle brook (inside joke) and rubber bushings at the axle there at least be some compromise. :D I think the guy wrote elder brock, was funny as hell. But the consistant revving was getting very annoying I must say. I think I speak for the rest of us here tongue.gif

</font>[/QUOTE]Elder Brock carb
Hi-Prof parts

and brand new rebuilt SB with 44 thousand on it. :D


Following this thread with great interest. Figuring on shaking my hotchkis arms on eaby and going with the elder brock as well. Might keep the hotchkis lowers and rebush them or maybe go with UMI instead.

Damn good stuff in this thread. I am glad I have folks to follow through this before I make a move on anything.

So is UMI offering a similiar bar to the Edel...? Just for arguments sake we used a rear sway bar on a road course stockcar and there was a considerable improvement over running without. Yes it was a 3 link with a panhard bar. Ralph

Obviously it needed more spring.

Yes, UMI is building an adjustable upper link with spherical bearing frame ends.

I have been following this post since the beginning as I have the rear end out and replacing the LCA/UCA’s …incredible wealth of information. I have already purchased lower boxed arms with rubber. For the uppers, I plan on sticking with rubber on the axle, but thinking about using adjustables purely to adjust the pinion angle…not for performance, but for tweaking out a possible pinion related vibration. Though because of this thread, I was concerned for it appeared that all adjustables used poly at the frame?

However, with the “new” to be built UMI’s and the spherical joint it shouldn’t be an issue…correct? I also stumbled across the following on Ebay…adjustable uppers with spherical ends $120.00 a pair.

upper adj (http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=33583&item=7952238365&rd=1)

One of the other pictures in his store for kits shows a box with “Chassis Engineering”….any thoughts?

UMI already makes adjustable uppers for 68-72 A body.

http://www.umiperformance.com/4017.htm

They're working on producing adjustable uppers for 66/67 and spherical end tube lowers for all A bodies. Denny says the lowers are due out any day now.

Herb, those are the exact arms I was thinking about running instead of the Edelbrock. Cheaper, and built just as well at the others.

Nice pieces for the money.

Dennis sure the car wanted more spring but as you know nothing beats getting the rear to lay down in the air, it really does great things with the aero. it also really helped corner speed as you could pick the throttle up quicker because it would squat and stick. We didn't like the results of the rear bar on ovals but who drives on ovals. Ralph

Dennis,great idea track testing different combinations! Eldeblocks (okay I`ll play smile.gif ) with rubber on the axle ends should be very interesting indeed. I suspect any additional bind will be offset by the superior axle location offered by the spherical ends but only testing will tell.
As for swaybars I don`t care for huge,high rate bars myself,as a rule. I generally like the smallest bars I can get away with without the spring rates getting uncomfortable. For vintage street cars I stress getting the geometry as good as possible first,then springs,and then bars after the fact to tune the cars behavioral characteristics. That said in come conbinations they`re almost unavoidable and not necessarily a bad thing provided they`re well integrated into the overall package at least IMO. Afterall Formula 1 cars even have swaybars front and rear. Marcus

Hi there! I just bought new upper and lower rear arms from UMI(polybushings)....Should I send them back or sell them or what ? Are the poly bushings realy that bad for my -70 Chevelle with a shorten 9" rear ????

Yeah, poly bushings are THAT bad.

Ok, my head is aching from reading all this and only understanding half of it (see my origin). What the heck is an elder bloke johnny joint? :D j/k.
Maybe someone could be so kind and put it in simple words for me.
I want to bring my worn out, sloppy rear axle suspension up to par with the front (New Ball joints, Polybushings, KYB's, 1 5/16 Hellwig Anti Sway Bar). I have installed KYB's in the back too. It doesn't have boxed LCA's and no anti sway bar. I thought about boxing the LCA's, getting the F41 Sway bar and using new poly bushings all around. Ok, I have learned, screw the poly bushings.
So what parts would you recommend? From what I have understood in this thread (wasn't much) I should keep the stock UCA's and install new rubber bushings. But what for the LCA's? I don't need the very best solution there is, I'd like a solution that is cheap, good and easy to install. Shipping an oversized anti sway bar to Germany will be extremely expensive, is there a good solution without it?

I'd appreciate brand names and part names, as i said I have problems finding the stuff you mentioned without that.

Thanks,
Olli

Olli, sit tight for a couple weeks. I'll have a brand name, a part number, and a super pricing plan available real soon.

I've been frustrated with wheel-hop since I got my '69 in 1981, but never really did anything about it other than a failed effort to install Lakewood ladders about 10 years ago. Otherwise the car handles well with 1 1/8" front stab., and correct ride height. I just want to be able to let out the clutch on wet pavement without the 12-bolt dribbling like a basketball. Based on the above posts, I'm going to leave the uppers stock and rubber, and install a set of Global West lowers, but I'm thinking about going Poly at the rear bushing solely for the wheel-hop. I've never had any use for a rear sway-bar.
What do you think Denny?--Thanks.

375HP 4SP 373 POS. Corvette Rallys, T/A Radials.

Actualy there a few rear sta-bars out there will help wheel hop. Look for frame mounted bars rather than arm mouted bars.

You would be better off with solid ends than poly, go with spherical bearings and relocate the upper link to increase anti-squat. I'm sure somebody is making kits, SSM is out of business last I heard but there are bound to be others. I don't follow the straight line stuff so I'm not sure.

Denny, will do. Please let us know when they are available. I'm gonna buy a pair too.

Thanks!

Olli

Where are these new bars by UMI?!?!

Patience grasshopper, patients.

Thanks to all for this site. I have a 68 that I ended up putting a big block in so I ordered a disc brake conversion kit and figured since I was going to be under the car...Anyway you've completely cleared me up on what I need to do for the rear. A friend who used to race European told me I would NOT be happy with polys in the rear, but my one question is for the front. I'm doing a complete front end rebuild and was wondering if I should just stay with OEM bushings or get a poly kit like one from Performance Suspensions. Any thoughts would be great. I was thinking of using front tubular control arms also. This is for a weekend warrior/summer cruiser. Thank you. If this needs to start another thread, I understand.

No polys in the rear. Not in any of the arms or any of the mounts, ever, even if if thats all thats available and you need it back together right away and your neighrbors brother says it will be fine. Never, never, never.

Clear enough?

Very clear. Since you didn't mention anything concerning my question about the front I'm assuming polys are ok there. Thanks again.

Supposedly, an adjustable rear upper arm was available from the factory. I've seen one set on a car and two on eBay, all were '65 Chevelles. They have an eccentric bolt on the diff. end. Can anybody verify that they were in fact a factory option and more importantly, any firsthand experience using them. My take on this thread is that with rubber bushings, they could be worth a try. Also, how about "No Hop" bars, obviously they relocate the upper arm, but is the geometry more likely to increase or reduce bind. Thanks Rowdy

Relocation devices shouldn't have much of an impact on bind issues.

I have not actually seen the adjustable arms from the early chassis but am quite aware of their existence. If you can get some, do so.

I did, a couple weeks ago on eBay, $102.00. A week later another set went for more, I stopped bidding at $120.00. They offer about 1/2" of total adjustment. On the bind issue, it seems that if the upper and lowers were brought closer to parallel, bind would significantly be reduced, however, I understand that "no hops" are intended to reduce (I think) the angle relationship of the arms (imaginary lines extended beyond the upper and lower arms would meet nearer to the rearend) or the opposite, it's late. Anyway, my inquiry had to with the whether the angle of the uppers (away from the diff. towards the doors) changed front to back at all. I have to believe that the crossmember pocket (upper front mount) would have to be altered. I think I answered my own question.
Say goodnight Gracie
Thanks for any input on any of this ^.

Originally posted by dennis68:
Olli, sit tight for a couple weeks. I'll have a brand name, a part number, and a super pricing plan available real soon. Denny, I will also be waiting for your info . Is it Global West you still recommend for lower Con. Arm's ??????

Nope, not GW. They are UMI arms.

DENNY, what about the poly bushings on the UMI arms?? I know your against poly bushings. Hard to view these arms as the best when there so much cheper in price than everybody else, which is a Huge plus...I'm ready to try it!!!!

Wait, the bearing ends are coming.

Don't buy into the whole pricing thing, cost does not equal quality. My QA1 ended links are very good quality and only cost me 120/pair.

Got it, I'll be waiting

UMI's package deal looks verytempting for the adjustable uppers and lowers for under $500. I think i will go for those and rubber on the third member as my combo is steet/strip.

can't wait for the pricing info dennis

BTW... thank you for all of your information and foot work

as far as ssm bars... lakewood took over the tooling and you can get the "a" body setup from them now

Okay the UMI QA-1 end uppers and lowers have been out for a while now and no one has made any eduactional comments about them. How are they working? The QA-1 chassis ended with rubber axel housing UCA any good? If this info is in another thread, I'm new, tell me where it is. Thanks this has been a great thread.

There are a number of companys that sell similar arms. The style is pretty popular in low buck circle track classes on the G chassis. In my experience heims don`t hold up nearly as well as bushings or Johnny joints on the street. We replace a number of them every year on customer`s cars because they were buzzing or rattling. They`re open to grit and water and you can`t grease them (with a few exceptions). Greasing doesn`t just lubricate,it displaces dirt and moisture. You can get "seals" for them which are a help but they`re vulcanized to washers so youl have to make room for them and they dry out and crack in a couple years at which point they do more to hold grit and water in than keep it out. For a couple dollars more than a good teflon lined heim you can get Johnny joints (or that type of joint from other makers) that articulate as well but last much longer and are sealed against the elements. Currie`s lowers with Johnny joints are competetively priced. Their uppers are pricey but they`re built like a battleship. If I were putting upper arms on healthy a street/strip car they`re the ones I`d use. For street cars the Edelbrocks are just fine and less expensive.
In reference to the SSM arms,note that they have no bushings. The bolts just go through welded steel tubing. Lakewood may have changed that but it doesn`t look like it in pics at least. They do improve traction but they cause a LOT of suspension bind on street driven (they make hard poly look like Johnny joints). We replaced a set on a 5.0 Mustang some years ago that had been street driven with the SSM arms for a couple years and all of the LCA mounting holes were egg shaped! We had to weld them up and re drill them before installing the replacement arms. Mark SC&C

Just an fyi, when i bought my edelbrocks the rep i talked to said they a guarranteed to 1200 hp. Teflon