Yep, crystal clear. Sitting in the driveway the stub axles are loaded. The strut rods brace the bottom of the spindle carrier, The weight of the car loads the stub axles toward the center of the car and the distance between the strut and the halfshaft puts about #300 of loading pushing stub axles toward the center of the car. Driving in a straight line with no side loading the same situation exists. (unless you hit a bump that unloads it and slams it back into the center pin) Everybody understands this.
Cornering hard to the right puts the majority of the weight of the car on the left (outside) tire. The point where the tire contacts the road has about 1800 lbs of pressure pushing the bottom of the tire toward the center of the car at 1G. The inner tire is almost unloaded at that point. (a sway bar reduces this weight tranfer) The strut rod is still fixed so it acts as a fulcrum and that fulcrum trys to pull the stub axle out of the differential housing. This overcomes the #300 of loading plus the additional load that the weight transfer on that tire puts on the stub axle and pulls the stub axle out if there is play between the stub axle and the center pin. (I know this is your theory, the extra downforce loads the halfshaft more). This effect would be compounded if you hit a dip or pothole during the cornering or the road was not level The sway bar diameter will also affect this. The front trailing arm bushing will keep the trailing arm from rolling completely so the axle does not come out of the differential. This tilts the top of the tire out. This is called positive camber; if the bottom of the wheel is farther out than the top, it is called negative camber.

Camber angle alters the handling qualities of a suspension design; in particular, negative camber improves grip when cornering. This is because it places the tire at a more optimal angle to the road, transmitting the forces through the vertical plane of the tire, rather than through a shear force across it. Another reason for negative camber is that a rubber tire tends to roll on itself while cornering. If the tire had zero camber, the inside edge of the contact patch would begin to lift off of the ground, thereby reducing the area of the contact patch. By applying negative camber, this effect is reduced, thereby maximizing the contact patch area. Note that this is only true for the outside tire during the turn; the inside tire would benefit most from positive camber. (IE: Nascar staggered camber settings)

This is why members here have stated "my car handled like a boat when cornering hard. Once the stub axle was replaced the problem was gone"

 

Thank you.

Obviously there two camps here- one that has either operated a car with no c clips or have taken the time to actually do the numbers, and the other camp that haven't, can't or won't do anything but bench race, but are convinced that this is devil's talk nonetheless.

I'll give 63mako a congrats that he gave it a good try, but didn't actually run the numbers far enough to determine when the positive load went neutral or negative if in fact it does. I was in the same camp as him (absolutely convinced, pounding the desk, red in the face) some years ago until I did the actual math. What's the old joke about the worst feeling in the world? Realizing halfway through an argument that the other person is indeed correct.

 

very good write, this is how i also see it ,,,, again, very good

 

I think it was much more than a good try, as I see it he nailed it...


Mike, you have been telling me to do the math.... and I do not see how the geometry lends itself to your theory...

So, I would like to humbly ask you to do the math for me and show me your results....

mike, although you believe as adamantly one way on this topic as we see the other way, the one main difference is that several of us have explained our theory in several different ways, but you just say "do the math" and then give no real reason or statement other than some saying "i've run with out c clips for years"..., and this proves what???

And I am not talking about sunday drivers, I run my vett like i stole it... and I am very familiar with its handling characteristics, and the car does not handle properly with to much play, for what ever reason, in the half-shaft .... been there, done that

So mike, please spell out, and do the math for me, ... I am very interested in seeing it....

And if you are correct, I will sit humbly corrected.

 

I would like to add some points to my most recent post. The trailing arm front bushing keeps the trailing arm from rolling excessivly. If these are in good condition the yoke will only pull out as far as this bushing flex or c clip if installed will allow and it would not be abrupt. It would gradually pull out as the G force increases and the shift to positive camber is a gradual shift except in the case of hitting a bump or dip while cornering. This might not be noticable to the driver, especially if he never pushes the car, other than his car does not corner as well as it would with a solid upper control link. My thought is all of you that have driven your cars for years with worn side yokes is that it is a gradual change as the wear occurs and you have never realized the full cornering potetial of your car so you have nothing to compare it to. It probably still handles as good or better than a solid axle car. Your car is properly aligned sitting on the alignment rack and the decrease in handling due to gradual shifting to positive camber when cornering could well be written off to "these old 15" tires just don't handle as well as modern tires" or "boy, the new corvette suspension is light years ahead of these old cars" (they hava a solid upper control arm) Both are true but not the total picture in this case. Those that did notice a reduction in handling and found excessive play at the side yoke and replaced them have posted here that handling was noticably improved. If there is math to contradict this I would suggest that it is a good possibility that there was an error in calculation, the weight tranfer differences due to different sway bar diameters and conection points (links vs solid mounts) and bushing flex (Old or new, rubber vs poly) will skew the results and might not be properly accounted for.

 

Mako, you were doing good up until you said this...

It doesn't overcome it. Sorry, it just doesn't. The geometry of the rear suspension is designed such that it doesn't. 300 lbs of preload doesn't sound like a lot when, like you said, you're loading that tire up with ~1800lbs. But you have to remember that force is working on you from the small end of the lever.

edited:
Allow me to go a bit redneck for minute...

Look at this thing. Please just look.


It's an unmachined, stamped out retainer clip that retails for $1.75. It does not have a bearing surface. It's got a nice big gap in it. And it can be spread apart with your bare hands. I know we love to bash GM here, but do you really think those engineers designed the weight of the car to bear down on THAT part. :

 

Has anyone here actually torn down the rear far enough to get at the stub axles and then ONLY replaced the stub axles and done absolutely nothing else?

anyone?

Oooooor did you also swap in new strut rod and/or TA bushings or wheel bearings etc?

Also did you get it realigned? And did you verify the alignment was correct with the worn stub axles?

I ask because decreasing the length of the stub axle as it wears down will also make your camber go more negative. If you let it get too far out, it could certainly affect the feel of the car. And then you slap in new (longer) stub axles, and the camber is corrected (or at least gets closer) and the car feels better. But that had nothing to do with the endplay really.

 

Quote: It doesn't overcome it. Sorry, it just doesn't. The geometry of the rear suspension is designed such that it doesn't. 300 lbs of preload doesn't sound like a lot when, like you said, you're loading that tire up with ~1800lbs.

I took a lot of time and effort to explain my position. I was clear and walked through it in detail item by item. This has not even remotely been matched by anyone with an opposing viewpoint. Nothing I posted in my last two posts has been contradicted by facts by anyone in any post on this or any other thread. I just hear "do the math" or "it just doesn't".
The above response doesn't make any sense at all , Sorry it just doesn't. The strut rod is about half way between the contact point of the tire to the ground and the centerline of the halfshaft. If you put 1800 lbs of pressure on the bottom of the tire pushing in you get 1800 lbs of pressure on the side yoke pulling out. If the strut rod connecting point was 2/3 of the distance from the centerline of the halfshaft down to the tire contact point on the road it would still put #600 of force trying to pull the side yoke out, more than enough to overcome the preload. The preload is 300 lbs. (not my number). What am I missing here?
The c clip is not the only thing holding the stub axle in (TA bushing, strut rods), as stated in the previous post it is loaded and unloaded slowly for the most part and has no need to be a bearing, it spins at the same speed as the splined gear the half shaft goes through and with it fit into the groove the clip is evenly loaded. The pressure is transfered to the end of the stub axle through the c clip in the groove. The c clip sees shear pressure. It is designed as it needs to be for the use it provides.
I am 52 years old. I was working on my homemade go cart when I was 8. Grew up in a farming family and have been working on mechanical things as long as I can remember. I was in honors math and automotive classes through high school, I took 3 years of automotive design and mechanics in collage. I have 35 years of experience building cars with a lot of custom fabrication experience under my belt. I don't have an engineering degree but I do have common sense, education and experience.
Here is a link to a C4 suspension. You will notice it no longer uses the half shaft as an upper control arm. It has seperate upper control arms as do most modern IRS This was done to eliminate the endloading on the sideyoke and the halfshaft being used as a control arm which in my opinion is a flaw with the C2-C3 design. They use it to adjust toe as well. The lower strut is fixed and non adjustable on these.
http://image.corvettefever.com/f/272...on_rebuild.jpg

 

Mike, do you still have your files, or do I need to reinstall my 20 year CAD package?

Look, the devil is in the details, and here are few you're missing.

1. The lateral loading of the tire is also resisted by the trailing arm bushing which is designed to flex for non-axial motion.

2. The strut rod mount is not positioned at the centerline of the hub.

3. The inner wheels are not completely unloaded even at 1g (hence the 3600 lbs / 2 logic you keep tossing around isn't really true)

And I'm sure I can think of more...

FWIW your credentials don't impress me, and nobody in this thread has provided any solid evidence to back themselves up. In the one camp, we have the people spouting off what they've always heard and believe instinctively. In the other camp, we have a guy who has proven himself on this forum many times who claims to have run a simulation and done the sums. And when I look closely at that suspension setup, I can't find any reason to doubt what he says. I have not run the sums personally, no. I admit that. Why? Because it's a lot of freaking work to setup the model, and I haven't had software for that purpose installed since college.

 

What you're missing is the downward force on the tire increasing (body roll) at the same time, but not at the same rate as the lateral tire force increase.

No I do not. This study was done several years ago with me looking over the shoulders of a couple of guys who were kind enough to run the model at work on their lunch time. I am retired now and do not any additional favours to call in. I was the loud-mouth know-it-all at the time who was convinced that the yokes would slap in and out at every little wiggle in the road and was dead set on proving the local diff guy (who had just rebuilt mine) that he was wrong. I used all sorts of half thought out theories and incorrect assumptions as arguments. Sound familiar? As I said above, there's nothing worse than realizing halfway through an argument that the other guy is right.

As you mentioned, it takes considerable work setting up the model in a CAD program to take in all reasonable variables. My hat is off to the GM engineers who got it right in the very early 60's using slide rules only.

 

Man you got that right. And it's that same can-do attitude that put men on the moon with a teensy fraction of the computing power that I'm using to post this. It seems simple enough until the details start piling up, and you realize you have to take into consideration things like the spring rate of a bushing, or the effect that the clamping force of a bolt has on a pivot, or simply the fact that nothing is completely rigid and on and on it goes.

 

Ok. So we are to believe this based on a cad program run x years ago by rearend guy x and over the sholder at that? You can't even verify there math or data that was imputed. O, and to ignore all logical thought of how we see this system set up? I have had the excess play in the halfshaft. After an alingment.... It felt like a boat on hard turns.... Fixed it... Problem went away.... What camp should you be in? I want to believe!!! Show me some writeup about it somewhere on the web... Anywhere

 

You realize I can spin that right back around at you, right? Verify for me that under normal driving conditions the vehicles weight bears down on that circlip. I bet you can't find anything more than anecdotal evidence for that one either!

Ask yourself this. What motivation would Mike have to lie about this? :

 

Sorry, that came off wrong, and yes you could spin that right back around... please let me rephrase. I could be wrong, dead wrong, and I would be ok about that, and I learned something...but I see it like this, on one hand I experienced it, I have studied the geometry of it, and to ME ..... I can not see how it is posable otherwise, but I am not a mechanical engineer ether.....

And then the other hand, did the numbers get put in 100% correctly into the cad program? was the program back then capable of doing this? I by NO means am calling anyone a lire, and if you took it that way, I am sorry, I do not disbelieve his report, I disagree with his source.... I just can see more wrong with one side than the other...

do I want to believe? yes...but it is difficult


another thought, when jacking up the car on one side to change the u-joint, I can attest that there is not 300 lbs of inward pressure, in fact there is a slight pull from or away from the rear end....hmmmmm... makes ya think??? and thats not in a hard lateral pull.....makes ya think...
and lets keep in mind, that c clip does not get pulled , like mako said the sheer strength of the steel is what to take into account, which I would bet is very high....

 

Seems like not much has changed. Show us something tangible, otherwise, you'll never make us realize we're wrong. -Jeff
Sorry in advance, just ribbin' ya. It's all in fun.

 

Those GM engineers installed a c clip and these cars rolled out the door with minimal side yoke endplay ending up with minimal in or out movement of the upper control arm (halfshaft/side yoke) under any driving conditions maintainig acceptable camber. Those GM engineers also installed an upper control arm designed to remove the halfshaft as an upper control arm when they finally redesigned the rear suspension system.(C4)

 

Addressed this previously, this will keep the sideyoke from pulling out completly but not from taking up the endplay and going farther without c clips.

Really, Who said it was? Just measured mine. The strut rod cenerline is 6 1/2" down from the centerline of the halfshaft. the center of the spindle is 13" from the bottom of the tire. this means if you have #1800 of side pressure at the tire contact surface means #1800 of force pulling on the side yoke.

No they are not completely unloaded but real close. Type and diameter of sway bar, sway bar connection type and the condition and material the bushings are made of will vary this considerably from car to car.

I really don't care if my credentials don't impress you. I have admitted I do not have an engineering degree. Just posted what I do have. Mike has admitted that he did not do the calculations but was looking over someones shoulder as they did them on their lunch hour and the results are no longer available. Do we know if this person was qualified? Do we know if the infomation put into the model was accurate? Do we know if there could have been an error in the way the model was setup? You know how calculations and computer models are Crap in, Crap out.

I have posted a lot of reasons to doubt this and seen nothing valid to support it. Have you read my posts with an open mind?

If you didn't run the sums, and Mike didn't run the sums and neither of you can post anything logical to dispute the information I posted how can either you argue with common sense and logic?

I hate getting sucked into this crap all the time! Just because someone has a couple more years of school and a piece of paper signed by a dean does not mean that they are any more intelligent or knowledgable on a particular subject than someone else, especially when there are numerous members that have had the problem, changed the yokes and solved the problem. This is real world facts and experience that I would put above someones buddy doing some math on his lunch hour with zero documentation or facts to back up what they are saying.
Wasting my breath and time.

 

Well, I'm out too since the strongest arguments seems to be that the 'figures were put in wrong' and 'the guys who did it weren't qualified.'

This, coming from the camp whose counterpoint so far is 'no it isn't, cause I said so' (pound desk, red face).

Funny how there's been several members who have come forward and stated that they've personally driven several decades with NO circlips and NO problems. How can this be explained? Are they mistaken also?

 

Wrong measurement, rotate yourself 90*.

Close only counts in horseshoes and hand-grenades. As I keep telling you, the devil is in the details. You can't just toss around formulas like (car weight / 2) and expect to be taken seriously.

This seems to be a pretty sensitive subject to you. Who brought up educations? Oh yeah, it was you. Yes, I have an engineering degree. Big deal ... show me ONE post where I have lorded it over someone.

No you absolutely have not. You've posted the same pedantic, anecdotal b.s. that you probably learned right here on this forum because it's been repeated here thousands of times.

Because it's not logical in the slightest! Here, this is what I saw and what my brain went through when I tore down my first C3 suspension. I'd heard all the fuss about excessive endplay and how it was the devil. So once I had my halfshafts out, I measured mine and found it to indeed be out of spec. So out came my pumpkin and stub axles.

Then I was in for a shock because I'd never actually seen those circlips before. Now I'm holding this flimsy strip of metal that I popped loose with a $3 pair of snap ring pliers. Surely this isn't intended to be anything more than a retainer! I thought to myself. It isn't machined. It isn't staked or heated on. It isn't even circular!

So what's the big deal with endplay? Endplay is just difference of the distance from the diff. pin to the circlip and the distance from the end of the stub axle to the circlip. But if the car's weight never comes to bear on this clip, then what's the real point of closing up the endplay?

Then I verified this for myself when I reassembled my rear suspension (yes with new stub axles ). I scribed a mark on both stub axles, and saw for myself that the stub axles only tried to pull out when the tires were completely off the ground. At any other time, they were pushed in. And as best I could tell by my examination of the positioning of the suspension links, the farther up the suspension travels, the harder the stub axles get pushed in.

Of course that's not a real world test is it? But that's where I stopped.

Mike went a bit farther. He enlisted the help of some coworkers and ran a model. The question is, does the lateral loading of the tire during cornering overcome the inward loading of the stub axle caused by the suspension geometry and the loading of the suspension? The answer was no, it does not at least not out to 1.3g.

I have no reason to doubt Mike's findings because they confirm mine. What research have you done? And FYI repeating what you've heard from other people does not qualify as "research". (I learned that in my fancy schmancy university )

Sorry, where's yours? I'll issue the same challenge to you that I did to Paul. Show me the documentation proving that circlip is more than a retaining clip and indeed is intended to support the weight of the car.

 

I understand you frustration, but your argument hinges on an observation of someone else, unknown to anyone else but you, at lunch inputing data.... who were they? why are they so qualified about C3 suspension? are you, and how can you be, so certain that all data entered was correct and accurate? out of the 100's of cad programs, what cad program did he run? how long ago was this and how old was the program?

An we are not in the camp of "I said so" as it looks to me, that is more of where you sit. We have had numerous people chime in, including a rear end guy stating that the end play is bad camp.... but you have the 20yo cad cam results.... hmmmm....

please give us more to chew on.... EVERYONE here, I would bet would love to know the truth, I am not offended in any way if I am wrong, I just believe we have a stronger argument, than the no C clips are ok camp....