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70Lemans
04-15-2006, 07:58 PM
I need some help piecing together the suspension for my car. I have read the posts for chevelles and have an idea of what I want, but am unclear on some details.
I'd like to focus on rear suspension first, because right now its jc whitney high lift springs and air shocks (needed them to clear the tires previously). Now I have a set of 17x8 245/45/17 front and 17x9.5 275/40/17 rear wheels and tires that will fit in the wheel wells.
I want to use springs instead of bags, and global west and hotchkis are pretty much out of the question from what I've read. I have read to start with 150 or 175lb springs and work up from there on a 72 chevelle, I guess a lemans would be similar. I'd like to know what are the best arms and bushings for the rear.
Plans for the car are mostly highway driving, and maybe some autocross when I finish the car. There are alot of hills and curves around here, but the roads arn't always the smoothest, so ride is important. basically, I'd like to put on the best stuff I can while keeping the c4l and not making the ride too harsh.( right now just about need to go to the chiropractor after driving it for a few hours, and I'm 20) any help is greatly appreciated.

sinned
04-15-2006, 08:11 PM
Spend a few hours scrolling through the suspension topic. Anything that applies to a Chevelle will also apply to your Lemans. There is a ton of information here, we have discussed these at length dozens of times.

andrewb70
04-15-2006, 09:07 PM
I have 140 lb/inch springs in the rear of my GTO. Why do you say that Hotchkis and Global West are out of the question?

Andrew

70Lemans
04-16-2006, 12:00 PM
before, I had only done a search for chevelle in suspension and read pretty much all of the hits that dealt with suspension, now Im searching other a-bodies (malibu, gto, ...) so I'll continue with that, it's just that in some threads someone may say that a certain bushing is good, and I'm not sure where in the suspension they're talking about. maybe it's there and my brain just stops soaking up info after a while, I dont know.
I was planning on doing the gw tall spindle upgrade until I read about the steering ratio and bumpsteer issues, and I think Hotchkis uses poly in the rear,which from what I understand is a bad thing. I'm not exactly clear on what to use in the rear, rubber, heim joints, johnny joints, or something else.

gearbanger
04-17-2006, 05:44 AM
All the poly does is add extra roll stiffness to the suspension. The same thing that a rear sway bar does and heavier rear springs. But for some reason, poly bushings are a horrible thing to do and springs and bars are the best thing since sliced bread. It is all theoretical BS. I don't know if you saw Dream Car Garage this weekend but they showed the Cuda supercar that they have been working on for some time doing some track testing. They were pushing the car pretty hard through the corners and the body was not rolling enough to move the tires up more than 1/2". With only 1 to 2 inches of articulation, poly bushings are a great alternative to rubber, and a much better idea than del-alum or solid rod ends. They give you the flex you need to dampen vibrations from the road, but are stiff enough to control wheel hop and housing wrap during hard braking.

If you are rock crawling with your car, better find a better alternative than poly, but if you are not, then poly is good.

sinned
04-17-2006, 04:11 PM
All the poly does is add extra roll stiffness to the suspension. Ummm, no. Properly used poly does nothing to increase roll stiffness, in fact it decreases roll stiffness. The same thing that a rear sway bar does and heavier rear springs. Springs and sta-bars increase roll stiffness in a linear fashion. Poly used in the rear of a C4L arrangement has nothing linear about it. It binds up until the mechanics of the suspension cause it to unload rapidly and without warning...snap-over steer. But for some reason, poly bushings are a horrible thing to do and springs and bars are the best thing since sliced bread. Simply adding springs and sta-bars is not the best thing since sliced bread. Adding the correct amount of spring and sta-bar will help handling though, as will poly bushings when used in a rotational environment...until they set egg shaped from poor cold flow properties. It is all theoretical BS. Well I guess in your expert opinion (you are some kind of an expert right?)I don't know if you saw Dream Car Garage this weekend but they showed the Cuda supercar that they have been working on for some time doing some track testing. Ahhh, well that is where you get you expert testimony from, a TV show where the sponsors pay huge amounts of money to get air time. They were pushing the car pretty hard through the corners and the body was not rolling enough to move the tires up more than 1/2". With only 1 to 2 inches of articulation, poly bushings are a great alternative to rubber, and a much better idea than del-alum or solid rod ends. You truly are way out of your league and have no clue what are talking about, lucky this is one of the "kinder" boards or would have a huge smack down on the way. They give you the flex you need to dampen vibrations from the road, but are stiff enough to control wheel hop and housing wrap during hard braking. Clueless...

My suggestion is to continue searching and add gearbanger to your ignore list that way you won't have to sift any meaningless babbling. Do searches for C4L, poly bushings, or search member’s names for posts. I have a few suspension posts, David Pozzi, Norm Peterson, chicane67, parsonj, Q ship, wally8, wendell, Salt Racer, Mean 69, Derek69SS, and a few others I have missed. Go to the "hardcore" thread that is stickied and look at some of the authors there.

Derek69SS
04-17-2006, 04:19 PM
:machine: ...while not the most diplomatic guy on the forum, Denny does speak the truth. :poke:

I had poly in the rear of mine... worst $100 I ever spent. :pat:

ProTouring442
04-18-2006, 01:53 AM
No poly on the rear, Denny is right on that. As for the front, call the guys at ATS. They have a nice tall spindle that doesn't have terrible bump-steer.... if they ever call me to let me know that my A-Body spindles are ready! :jump: They haven't started making the A-Body version yet, but soon!

Shiny Side Up!
Bill
'72 442 "Inamorata"

gearbanger
04-18-2006, 09:14 AM
:injured: :injured: :injured:

I have been beaten up by the theoretical racer Dennis!

sinned
04-18-2006, 09:29 AM
You won’t see me jumping into any of the SCCA boards or NASA boards claiming I know more than I do either. I have no problem admitting my actually road course track time is limited to a few events.

I also know my limitations, I tend to stay out of the fabrication topic as my welding time is limited to putting tractors and underground construction equipment back together, I also don’t jump into the FI topic telling the guys who tune for a living that they don’t know what they are talking about.

gearbanger
04-18-2006, 09:44 AM
Okay, then without being abrasive, how would you quantify the difference between the performance of theoretically perfect three link (no roll stiffness added and spherical rod ends and all that) versus a good factory four link set up with strong boxed control arms and poly bushings.

This is what I think. The roll stiffness added by the poly over such a short range of motion is negligible compared to that of the springs and the antisway bar. The road feel is better but not harsh like spherical rod ends.

I would love to hear from someone who has made the change from a factory setup with poly to the three link with with rod ends and no other changes and see what their improvement in performance was.

sinned
04-18-2006, 10:42 AM
The usage of mechanical bind (converging links to control lateral location) and poly urethane (to increase roll stiffness even more by removing the rubber deflection) is not an ideal method of controlling stick axle position as it allows other devices than the springs, shocks, and sta-bars to dictate overall roll stiffness. The methods of controlling axle position should not have any impact on stiffness what-so-ever, this is a job for controlled devices; things that can the user can adjust, change, or tune. Mechanical bind is not something can be adjusted or tuned as it is not supposed to be there to begin with. To use the sta-bar theory is not even a close similarity. The sta-bar is a very controlled linear increase in roll stiffness where the user determines how much to add and how quickly the increase is to occur. Mechanical bind varies depending on the exact position of all the links and the exact point of release will be different at every corner so predicting where the snap-over steer point is impossible.

Running a properly designed and installed 3-link with spherical ends will ride no worse, in fact probably better than a C4L with poly and boxed arms. The design of the links is to articulate freely and not interfere with the movement of the axle.

DonQuehotey
04-18-2006, 02:46 PM
"Running a properly designed and installed 3-link with spherical ends will ride no worse, in fact probably better than a C4L with poly and boxed arms. The design of the links is to articulate freely and not interfere with the movement of the axle."

Sorry D.... I dont buy it man. A heim end is a solid connection with no ability to absorb harmonics or frequency unless you are talking about the minute amount of teflon in a lined rod end so the harmonics or vibrations will be transfered through the connection point to the chassis. A poly bushed rod end will in fact absorb some harmonics / frequncy and not tranmit it through the mounts. Also not to mention that a rod end will be a high wear item especially on a car that will be seeing miles of road grime..... a track only car... hell yeah! but not a driver.....

ProTouring442
04-18-2006, 06:06 PM
OK.... A converging four link requires arms to bend, bushings to deflect, and arms to get longer or shorter in order for the axle to articulate. Poly bushings and boxed arms will make it nearly impossible for any of this to happen. Steel doesn't stretch very easily, and poly won't deflect. Soooo, the diff will pop up and down like an oil can, snapping from one position to another. I am no suspension expert, but crawl under your car and look at that thing, it just doesn't work without rubber in it.

Shiny Side Up!
Bill
'72 442 "Inamorata"


"Running a properly designed and installed 3-link with spherical ends will ride no worse, in fact probably better than a C4L with poly and boxed arms. The design of the links is to articulate freely and not interfere with the movement of the axle."

Sorry D.... I dont buy it man. A heim end is a solid connection with no ability to absorb harmonics or frequency unless you are talking about the minute amount of teflon in a lined rod end so the harmonics or vibrations will be transfered through the connection point to the chassis. A poly bushed rod end will in fact absorb some harmonics / frequncy and not tranmit it through the mounts. Also not to mention that a rod end will be a high wear item especially on a car that will be seeing miles of road grime..... a track only car... hell yeah! but not a driver.....

sinned
04-18-2006, 07:00 PM
Why Don, why is it you insist on arguing basic geometric and physics almost on a weekly basis?? OK, let me simply it for you. In a properly designed and installed environment there is nothing to transmit as the links are free to articulate and none of the jarring forces to the suspension are working against the links. The links run parallel and perpendicular to the vehicle centerline; jarring forces of normal road conditions force the suspension vertical, movements the links are not responsible for controlling. Good shocks and springs take care of that.

BTW, I run all rod ends in the rear and a combination of solid and Teflon bushings in the front. The closest my entire chassis has to compliancy is the polyurethane body bushings. I drive it everyday in all weather conditions and even with 1” of travel ride is no harsher than 2006 F350’s we run at work.

ProTouring442
04-19-2006, 02:22 AM
The closest my entire chassis has to compliancy is the polyurethane body bushings. I drive it everyday in all weather conditions and even with 1” of travel ride is no harsher than 2006 F350’s we run at work.


I don't mean to hijack the thread, but where did you get the poly body bushings?

Shiny Side Up!
Bill
'72 442 "Inamorata"

gearbanger
04-19-2006, 04:33 AM
Dennis, you are correct in everything you say, in theory. But, it doesn't yeild measurable results. If the rear doesn't articulate then it doesn't matter what kind of bushings you have in it or what kind of link arrangement.

Also the center links of the factory 4 link are close enough together that it takes very little flex to allow the rear to articulate a couple of inches either way. If you could come up with some measureable results, it would be great. All this three link effort is just not going to be worth it in actual gains at the track. But if it makes you sleep better that you have absolutely 0 in/lbs of bind in your rear axle then I guess maybe it would be worth it anyway.

sinned
04-19-2006, 05:15 AM
Actually gearbanger, you are completely incorrect, the C4L with poly bushings takes approximately 67lb/in to move compared to ~4lb/in with spherical bearins. This is in a C4L environment. If you remove one the converging links in the later tests (making it effectively a 3-link) the results drop to virtually zero.

The rear is not the part requires articulation; it is the links that need to articulate by the very nature of how they are designed to operate.

Not worth the actual gains huh? What criteria need to be met to justify the extra effort? No, it won't take a last place zero to the hero position but it will produce a faster lap time and make the vehicle much more predictable to drive, inspiring confidence.

Bill, check Original Parts Group.

DonQuehotey
04-19-2006, 06:23 AM
"I drive it everyday in all weather conditions and even with 1” of travel ride is no harsher than 2006 F350’s we run at work"

How can you legitimately argue ride quality and correct geometry when your reference is that it rides like a 1-ton truck and has an inch of travel. In your world it seems like a shifter cart would have a good ride quality......and with only 1" of travel.... who needs articulation or proper geometry...... :) as far as argueing with you on a weekly basis, sorry if I do not jump on to the Dennis is the always right king wagon... I simply dissagree with some of the stuff you post. There is nothing wrong with that.... Its all about becoming edumacated right?

gearbanger
04-19-2006, 06:35 AM
Actually gearbanger, you are completely incorrect,

How so? I said that the poly bushings added some roll stiffness. So are you saying that with no springs and the rear end in its natural position, it takes an additional 67 lbs to move the tire up 1". I doubt it, but even so, how many lbs, would it take to twist the rear stabilizer 1"? Much much more.


The rear is not the part requires articulation; it is the links that need to articulate by the very nature of how they are designed to operate.

The rear end does require some articulation. If the body rolls the rear end articulates. You are partially correct though, if the body doesn't roll, then the rear doesn't require articulation.


Not worth the actual gains huh? What criteria need to be met to justify the extra effort? No, it won't take a last place zero to the hero position but it will produce a faster lap time and make the vehicle much more predictable to drive, inspiring confidence.

A gain. You won't see any gain on the track from making this change. Yes, it is a better idea if you are starting from scratch, but the factory set-up gives better ride characterists, is simpler in design, and will yeild the equal or very nearly equal performance in a handling situation. You are making compromises for little to no gain.

sinned
04-19-2006, 04:53 PM
Actually gearbanger, you are completely incorrect

How so? I said that the poly bushings added some roll stiffness. So are you saying that with no springs and the rear end in its natural position, it takes an additional 67 lbs to move the tire up 1". I doubt it, but even so, how many lbs, would it take to twist the rear stabilizer 1"? Much much more.

Oh how they hate when we do this but it's easier for me. You are wrong here-


Also the center links of the factory 4 link are close enough together that it takes very little flex to allow the rear to articulate a couple of inches either way

The upper links which dictate lateral location only need move a few hundreds of an inch for the mechanical bind to come into play. You doubt the data provided? Really, well since it was provided by MM you should call and tell them you think that one of the most respected members in the road racing community is full of crap. Odd that NO ONE else has ever questioned the validity of his test.

Again, you don’t seem to grasp the whole linear vs. non-linear theory. The sta-bar may very well add more roll stiffness however it is predictable and adjustable…mechanical bind is not.



The rear is not the part requires articulation; it is the links that need to articulate by the very nature of how they are designed to operate.
The rear end does require some articulation. If the body rolls the rear end articulates. You are partially correct though, if the body doesn't roll, then the rear doesn't require articulation.

Sure it needs some articulation, but not like a rock crawler, the upper links on the other hand require quite a bit of articulation to work properly (something that boxing and using poly make very difficult).



Not worth the actual gains huh? What criteria need to be met to justify the extra effort? No, it won't take a last place zero to the hero position but it will produce a faster lap time and make the vehicle much more predictable to drive, inspiring confidence.
A gain. You won't see any gain on the track from making this change. Yes, it is a better idea if you are starting from scratch, but the factory set-up gives better ride characterists, is simpler in design, and will yeild the equal or very nearly equal performance in a handling situation. You are making compromises for little to no gain.

You honestly believe going form a C4L to a 3-link would not show measurable gains in lap times, you really are crazy and have no idea what you are talking about. Hell, DSE just got done with test showing and saw huge gains going from a leaf arrangement to a 4-link (though I somewhat question the validity).


[COLOR=black]How can you legitimately argue ride quality and correct geometry when your reference is that it rides like a 1-ton truck and has an inch of travel. In your world it seems like a shifter cart would have a good ride quality......and with only 1" of travel.... who needs articulation or proper geometry

The reference was only to show that rod ends do not necessarily equate to harsh ride, and if you had ever driven a newer full-size truck, they don't ride bad at all, just a little stiff. The "travel" reference was in error, I actually have about 2.5" of total travel, and an inch is downwards. While it may seem fairly small, in a C4L any movement at all requires the proper geometry as the links are constantly fighting each other.

As for the constant “heated discussion”, you claim to be interested in learning yet you don’t ever seem to grasp it. No matter how much information is laid out in front of you there is always something that you can argue, that is not learning. I think somebody just likes to play Devil’s advocate.

gearbanger
04-21-2006, 07:05 AM
Dennis, you have never ever posted any real world information to back up anything you have ever said. All your theories and "knowledge" is based on what a computer or a cad drawing tells you is better.

So yes, I agree that 3 links are better and the C4L but not enough to go through the trouble of doing it for anything less than an all out race car.

Same for spherical bearings, not worth the trade off in a street driven car.

Same for the tall spindle coversion, it is a very, very good upgrade and well worth the money. Your spindle idea is going to be very nice, and if you can figure out how to put a factory set of big brakes on it that someone could get at the boneyard cheap like the B-body stuff, then you may actually have come up with something worth doing for the other 95% or the people reading this forum.

Till then, I guess you, Derek, and MM will just have to continue to sit around and stroke each other. :)

Derek69SS
04-21-2006, 08:03 AM
Till then, I guess you, Derek, and MM will just have to continue to sit around and stroke each other. :)Given the choice, I'd rather do that than take it up the ass from one of the poly bushing makers again... worst $100 I ever spent. :slap:

Elusive R
04-21-2006, 09:30 AM
I would love to hear from someone who has made the change from a factory setup with poly to the three link with with rod ends and no other changes and see what their improvement in performance was.

Okay, I'll bite and maybe help bring this topic back to tech. Since I have a 3-link (although not theoretically perfect) on my El Camino, I suppose I can help a bit.

I'll start by saying that poly in a 4-link is not the end of the world. Is it great for an all out race car? No. But it is driveable. The problem with the poly-bushed, boxed arm setup is that it attempts to control lateral axle movement with pure stiffness. This works great and gives predictable response (to a point), but sacrifices ride quality and does allow as much articulation. It feels very responsive but once a limit is reached, it's all oversteer. This can even be fun, but many (Dennis included) won't like it and on a bumpy track, I'd imagine the car would be a handful.

With a 3-link, the articulation that GM gave the car originally returns but there is no added articulation stiffness, if you will. You're using nearly pure spring and shock control, so it's smooth, predicatable, and honestly, awesome. The biggest change I noticed around town was how nice it rides. It rides like it used to with the open channeled, rubber-bushed C4L but the rear end does not move a bit thanks to the panhard rod. The only rod end I'm using is at the PHB to rear end mount, everything else is Howe rubber bushings and the old poly is still in the LCA's, but it doesn't have much effect there anyway. Overall, I love it. I don't get any kind of harshness at all from it - but I'm sure I would if it were all rod ends. I actually seem to have a bit more traction with the 3 link, although not in a launch situation - but out of corners it bites hard enough that the only oversteer I've managed is throttle induced. Take that for what it's worth, though, I have zero track time on the car and probably won't for some time (money, money, money).

Ryan

gearbanger
04-21-2006, 09:46 AM
Derek, I was just prodding Dennis a little, I didn't mean anything against you. I actually have alot of respect for all of you guys, I just can't stand to hear someone say that their way is the only way and everything else "sucks". That is all. And only one of the three I mentioned does that.

Elusive R,

That was a great post, I really appreciate that real world direct seat of pants comparison. Did you build your three link, and if so, did you do any calculations on the geometry as far as the antisquat compared to the C4L? I had a set of no-hop bars on my GTO C4L and it really made a huge difference in the launch traction. I assume that if you had the correct geometry you could still have the antisquat with the three link, but that is probably not a benefit in a handling car. The rear of my car would actually lift during hard acceleration, so under a hard decel, I'm sure the rear was being sucked up in the chassis.

Post some pics if you get a chance.

Elusive R
04-21-2006, 09:55 AM
Gearbanger,
Go here:
http://www.chevelles.com/forums/showthread.php?t=110734
and here:
https://www.pro-touring.com/forum/showthread.php?t=12946

Yes, I built it and did all the calculations. Anti-squat with the three link is less than what I had with the C4L, but that was by design - the numbers should be in those posts as I don't remember now what they were. The SVSA was more important to me since I don't drag race (except just to see how fast the car is).

Ryan

sinned
04-21-2006, 04:29 PM
You didn’t really go to the "tall" spindle did you? Anyone who has even an inkling of geometry understanding knows that the tall spindles suck big turds and yes, I do have first hand knowledge from multiple attempts at making that gigantic pile of crap work.

I'll tell you what, you bring out your GW/Hotchkis/what-ever other magazine ad you got your parts from ride out and I'll embarrass you for a while so you can see how cars set up correctly work. How’s that for real world experience?

gearbanger
04-21-2006, 06:32 PM
What are you going to embarass me with, your car is setting there with the tall spindles and a C4L in it. Are you going to embarass my GTO with your computer program.:bsjerk:

You just keep saving your allowance and maybe one of these days you can drive your car again cause it won't "suck".

sinned
04-21-2006, 07:00 PM
Hello, foot...in mouth. You don't know what I have, so what the hell are you talking about?

You’re about to get "named" Yodi as you come into threads with absolutely zero tech to back up any of your claims and crap all over the thread. No offense to Yodi, I actually liked him better.

zbugger
04-21-2006, 07:40 PM
Play nice boys. I think this thread has been hijacked enough. Did it even answer the original question?