Steve, by your own admission you apparently don't have a clue how altering IC's, RC's, camber gain and the like may be of benefit to anyone seeking to improve the handling of their car, yet the lecture continues. Your 18% theory alone brings into question your understanding of trigonometry (I aced that in college, btw), and is damning evidence IMCO you don't know a whole lot about camber curves. Vehicle dynamics (it's a package deal that can't be broken up) is one of the most complicated areas of automotive engineering, and I'm no expert at it, but at least I don't need floaties to swim in the deep end.

And, yes, as a matter of fact I have "seen" eccentrics move. Or, more correctly put, I have observed them fail to hold static camber adjustment. Proper adjustable camber struts replace the eccentrics with camber lock plates.

 

Aftermarket Poly struts BIND! the strut rod rotates in its movement, it has been covered enough already. Until someone "smartens up" and puts a "johnny joint" style spherical joint on one of the poly kits I wouldnt go with a poly setup. The race struts with metal Heim ends require you to inspect them for signs of failure. The Heim ends also don't care much for road grime if you drive in wet conditions. If you have early (74 and below strut rods) the replacement bushing with it's metal outer sleeve takes out 20-30% of the rubber that was once in there and they work really well in most conditions.

 

Apparently you only read about 10% of what's being written here. I have a very good understanding of the suspension design, and what I admitted to not knowing was what the target camber change in a road race application is. Obviously neither do you.

So instead of yammering on about how much you know, why don't you jump in with your own calculations and illustrations and show us how and why I'm wrong? So far all we've read from you is thank you's to Noonie for doing a calculation you didn't know how to do and unsubstantiated claims about how an 18% change is all wrong.

It's time to put up or shut up. If you've got proof I'm wrong, let's see it. If we don't see it, we can only assume that you're just shooting off your mouth. And so far, that's all we've seen.

Oh yeah, let's see a pic of that "slipped" eccentric. Google the net for one if you have to. I've got a sneaking suspicion that this is where the rest of your "knowledge and experience" comes from.

Steve g

 

I was thinking about replacing my VB&P poly strut rods with Heim ends, I have been told that using these seals will help them to last, any truth to that?



Just found these rod end boots as well:

 

I've used the washer type for several years, but with heims that have no zerks. I have not seen any water or dirt under the seals but I do keep them filled with MolyD grease which is used extensively in underground mining machinery because of the harsh dirty wet environment. I use a needle adapter with a grease gun to inject grease under the seals.

The full boot looks interesting.

 

Steve, seriously, are you so caught up in your own little theories that you aren't even aware there is no such thing as a one-size-fits-all optimum setup, let alone camber curve???

Is your view of vehicle dynamics so narrow that you believe there is nothing more to it that can't be explained to your satisfaction with a couple of simple equations???

Given your penchant for bickering rather than paying attention, convincing you of anything you don't already grasp may well be impossible, but in hopes you might actually be able to put that aside for a couple of minutes I'll try to draw a picture for you...

First, lets look as the basic camber requirements for drag racing a car with sufficient power to need slicks. It should be obvious that for this particular purpose it's all about putting power down in a straight line and staying hooked up. Ideally, you'd want the rear tires to be and remain square to the road surface to maintain maximum footprint, and thus zero camber gain (or as near to it as one can get) is broadly accepted as the going setup at the strip; however quickly and however much the car in question squats during launch, or at what ride heights it travels to the finish line. True, torque roll sometimes requires compensation, but IMOE (and I've won an awful lot of rounds in my day) that issue is better dealt with by shock and/or spring tuning.

Next, lets look at camber requirements for an under-powered autocross car. Since such a vehicle isn't able to spin the rear tires under acceleration, any idiot can plant their right foot on the go pedal with equal results, so the key to better lap times is going to be maximizing cornering capacity (said idiot aside). In order to do that the amount of camber gain at the outside rear tire needs to exactly counter the total amount of bump occuring at that corner while the chassis is in roll. Sounds simple enough that there ought to be one camber curve that would work for every C2/C3 out there, right?

Wrong. Variables including vehicle weight, weight distribution, weight transfer, unsprung weights, center of gravity, spring rates, spring frequency, roll resistance, roll couple distribution, toe, toe-steer, bumpsteer, Ackerman, brake bias, track width(s), tire characteristics, etc. all factor into determining just how much total bump occurs in roll during cornering. And, we haven't even mentioned that not all road surfaces or turns are the same, or how weight transfer rates simply cannot match with them all.

Now, lets add a big dose of excess power to that car and put in on a road course with slow corners and long straights. Since the key to lap times is going to be keeping the rear tires planted during long periods of acceleration from slow speeds down the straights, camber requirements will head in the direction of those suiting the drag strip (tho zero camber gain is never really the best setup for anything that takes turns). Take this same car to a track with a mix of turns, and the optimum setup will be somewhere in between. Still with me?

Another huge variable which factors into camber requirements has been the steady development of tires. Regardless of one's purposes, whether as extreme as the above examples or as tame as cruising to the show-n-shine, modern radial tires don't require as much camber gain to work to their optimum potential as did the bias ply tires being produced back in the day (some 40 years ago, if you haven't noticed) when the C2/C3 IRS was first engineered. Even the C3's reduced camber gain (by virtue of lower inner camber strut links relative to the C2) is more than necessary with today's tires.

Understanding this progress has changed the game, I subscribe to John Greenwood's recommendation to lower the inner camber strut links by 1/2" inch below the stock C3 height (relative to the diff) as the default setup anyone running radials ought to adopt, in lieu of a better adjustment being found thru testing. The most accurate instruments by which one can arrive at the optimum camber curve (as well as other settings) for a given car, driver and purpose include the stop watch, a tire pyrometer, data acquisition and (depending on his skills) the very sensitive one on which the driver sits.

Notice that I didn't say anything about theoretical examination in the above. That's where one strives to come up with a sound baseline from which chassis tuning only begins.

Did the General do the math? Certainly.

Was Zora a genius? Anyone would be a fool not to acknowledge that.

Was he satisfied to stop there? Absolutely not, as the real work happened on the test track.

Did they attempt to account for as many varying conditions, roads, drivers and purposes as practical? You bet they did, however, by definition that's precisely why the C3's suspension geometry is a compromise (budgetary restraints notwithstanding).

Bottom line: Might you try to set aside your low opinion of me (or anyone else who may challenge what you believe you know) long enough to allow anything I've said to start sinking in? Or, do you require yet more rope? I sincerely hope it's the former, as there is nothing in it for either of us if you are determined to continue on your current tack.

Before I conclude, you should know I usually just put people that irritate the crap out of me straight onto my ignore list, but I've made an exception for you, because you seem like you might be an intelligent guy who could become an asset to the CF. Then, again, I could be wrong, and in the end may wish I'd taken the other route. Your call. I'm done...

TSW

 

You know, I didn't even read your whole ramble. It is totally off topic and simply reiterates what I've already said.

Had you actually followed the discussion you would have known that the topic was about changing the length of the strut rods in order to set camber at it's resting static position.

The first point that I took exception with was that changing strut length is exactly the same as moving the pivot point. It is not. If you are in disagreement with that, let's start there.

However, if you have realized that control arm length and the difference between the length of the upper and lower is how camber change through the suspension travel is achieved, you will know that statement is wrong.

The popular position then changed from exactly the same to saying that the amount the length of the strut was changed to achieve correct static camber when the oe adjustment has run out is insignificant. I asked how you knew that and that's where we stand. I did not say that suspension shouldn't be changed for different purposes or to achieve something to better suit your tastes. In fact I did say that you would alter the strut length to achieve a desired race influenced effect and said I did not know what that target would be.

My position remains that if you are using the length of the strut rod to compensate for loss of camber you have no idea what you're doing to the geometry. Nobody here, yourself included, could even answer the question as to what a 1/4" to 1/2" arm length does to camber change.

Only an idiot would sit there and say shortening the strut rod to achieve adequate camber would provide an improvement over factory designed rate of camber change. You don't even know what you've created. How can you know if it's an improvement. And in all probability you no longer have the same camber change on the left as the right.

When you are planning on an improvement to the oe system, you do like Kaos did. You set a target of how much camber change you want to achieve through how much suspension travel. Then you play with the lengths of the control arms to achieve it.

So if we're now clear on that and have you back on task, and assuming your entire off topic rant wasn't an attempt to muddy the waters so as to avoid a question you still can't answer, the challenge to you was to substantiate your claim that a 1/2" change in lower strut length creates an insignificant alteration to camber change.

I provided my reasoning, the difference in the lengths of the two arms is what creates the camber change and there is only a 2.750"inch difference between the length of the two arms, so a .500" reduction in that difference is an 18% change. I proposed it could make an 18% difference. I may be wrong on that, because it is not a straight line corelation. This is where you show me the math and prove me wrong. Once you've done that I will post the sketches I made and the high school geometry that helps explain this.

As to your last paragraph, I really couldn't give a rat's *** if I was on any list of yours. If you think I post here to so I can become your friend you are seriously delusional.

So the challenge remains, support your claim that the 18% change to arm length differences is insignificant . "The Skunk said so" doesn't cut it with me.

Steve g

 

 

You started in this thread by saying that changing the length of the lower strut is critical and would defeat the original design.


As I said before, I’ll stand by that statement.
I showed you that the difference between the two is realistically immeasurable at ¼”, the thickness of 2 sheets of paper. I don’t know of anyone that can set camber with any type of machine that accurately and I have put my time in doing that over the years. In fact it would be extreme luck to even set an adjustable strut .007” longer or shorter.


Why bother, the difference is immeasurable.


I still don’t understand how you are hung up on these percentages.
You are shortening the lower strut by what you say is 18%.
In order to compare the oem to the adj strut you must also move the eccentric by the same 18% and calculate any difference.
The resulting difference probably will be the same .007” as I previously calculated. .007” difference is no where near 18% change in the geometry.
BTW, I have never had to move an eccentric or adj strut .500” to set camber anyway.

I asked you before to show any calcs that show the strut defeats anything oem.

 

Steve, given you can't be bothered with reading my last response, which included a few things you ought best come to understand, you rather obviously can't tolerate that someone other than yourself might actually know what the hell they're talking about.

I can see no useful purpose in further effort to share anything that might otherwise have been of worth to someone with an open mind with you. So I won't.

Oh, and be sure to celebrate your victory with a diatribe about how you showed me up.

 

You are not changing the strut length by 18%. You are changing the difference in the 2 control arm lengths by 18% and it's the difference in the two lengths that determine how much the camber changes through it's travel.

Clearly you are still not picturing it. Moving the eccentric does not alter at all the relationship of the bottom arm to the top. It is the ratio of the two lengths. When the eccentric moves the bolt, the point that the 16.750" arm pivots on, moves. It is still a 16.750 arm moving in sync with a 14 inch arm, the outer end traveling in different arcs. I don't know how else to illustrate it to you. A 16.750 arm's outer end moves in a circle. It doesn't matter where you position the pivot point of that 16.750 string with a weight on the end, it still makes the same circle. However if you change the length of that arm (string) the outer end is no longer traveling in the same circle. Now you have a 16.5 or a 16.25 arm moving in concert with a 14.0 in arm, each traveling in it's own arc.

You haven't seen a .500" inch change in arm length? Well that may be, but I'm sure it happens to people following your advise about getting adjustable length struts when the run out of adjustment.

I measured the distance the eccentric moves the pivot point. It's entire travel is .750". That makes it 3/8" from centre to the end of it's adjustment. If someone can not bring their camber into spec because they have run out of adjustment they will use that entire 3/8" plus whatever they were short when they ran out of adjustment. When you install your adjustable rod you centre the inboard bolt in the eccentric's slot. There's your 3/8". Is conceivable that when they ran out of adjustment they were still 1/8" away from accomplishing adjustment? Not only is it conceivable, it's likely.

I had some better hand drawn illustrations, but they're at work. I've posted one I did quickly a couple of minutes ago. That along with this calculator will allow you to do your own calculations.
calculator to do the math.

Using this illustration,


picture the pivot point as the xy intersection. This is showing 4" of travel, 2" above the horizontal and 2" below. The actual travel of the ends will be an arc. But we're not interested in the arc. If 16.75 is the distance down the x axis to the furthest out point the arc travels the line drawn from the ends of the arms when they have traveled in their arc represents the inward movement of the outer end through it's travel. We don't need top and bottom, but either one forms a right angle triangle. We know two of the arm lengths and one of the angles in degrees and from that we can calculate all the other dimensions. By subtracting that horizontal distance from the arm length we can determine how far the outer point travels inwards in 2"inches of travel. This is the line on the x axis to the right angle.

So using the calculator the upper control arm (half shaft) at 14" moves inward .144"

The lower shaft at 16.750 " moves towards the y axis .120". Which means the top moves in .024" more than the bottom, and that's what creates our camber change.


Now if the lower arm is 16.250" it moves inward .124", only .020"inches less than the upper.

Now there is a direct linnear corelation between distance moved inward and degrees of camber. It is moving .020/.024 of it's previous amount, or 83% of it's previous amount of camber change at 2" from horizontal. That's 17%.

Now this is over simplified and assumes a paralell system with shafts horizontal at rest. Changing height of one of the pivot points changes the amount of change and would take a little more information and time, but the principle is unchanged.

Steve g

Edit, when using the calculator, you are entering 2 for side a (vertical travel), the rod length you are working with for side c and angle c is 90*. Your result will give you side b. Subtacting side b from side c gives you how much the outer point traveled inward along the x axis.

 

Can't say I wasn't expecting this outcome. Pretty common when someone gets called to task after shooting their mouth off.

You didn't need me to show you up. I think you manage that well enough by yourself. Anyone that followed your brilliant U-joint vs CV joint (AKA Apples vs Fruit) thread where it took you 2 pages to discover what everyone else figured out in the first lines had a pretty good sense of what you're about.

Steve g

 

Thanks for the tutor on the geometry.

I didn't see where you compared the adj to the oem strut in your calcs (after all this is what this whole discussion is about), but yet you said that the pivot point doesn't matter.

Here is the comparison of oem vs adj heim calculated previously at 1/4".

Since you are so into percentages, the difference between the oem and adjustable at a full travel (at least at the 1/4" setting) is 0.7%
It should be safe to say that the maximum camber change would also be 0.7%
The recommended camber for touring, according to Guldstrand, is 1/2° neg which would translate into .0035° difference. Keep in mind this is at max 4" travel, less travel will be less difference.

As per my original statement, adj and oem are the same, it's realistically immeasurable

 

There's something wrong with your drawing that needs to be cleared up before we can continue. Leave your arcs where they are and move your radii to the horizontal position. How can the one arc move toward the other when moving in in the downward swing and away from it in the upward swing. In order for the point that the two circles intersect to be at the point you show you would have to move the pivot point in that direction. But the pivot point doesn't move that way, it moves on a horizontal plane. So the arcs will be at their closest points horizontally and moving away from each other as they travel up or down. If you move the pivot horizontally the arcs will intersect in line with that horizontal movement.

But that's not what's really missing. How can you quantify any of this without reference to any of the dimensions it works with. Camber doesn't change because the strut moves in an arc. Camber changes because the strut moves in a larger arc than the arc the halfshaft moves in. And it's the difference between the upper and lower arms that creates the camber change. So with no calculations about the upper arm how can you say .007" is nothing.

Granted my calculations presume a parallel arm system but what it does illustrate is that the difference in horizontal movement of the upper and lower control arms is only .024". However they are configured you are not working with a large amount of movement. And that's what makes my calculated .004' (@ 2" travel) and your .007" travel @ 4" travel) become very significant.

Steve g

Edit. You don't create a percentage by moving the decimal point of a measurement over two digits. A percentage is a comparison of two things of the same units. .007" is 10% of .070", it is not 10% of .070'. If you want to create a percentage out of your .007" you have to have something else to compare it to. My calculations take the difference in the amount of movement and compare it to one of the actual amounts of movements and calculate the percentage from there. So to that end, what is you .7% a percent of?

 

I think it may be about time that you might want to correct your original statement that the struts defeat the original design. That just isn't the case.
Trying to repeatedly cloud the issue with erroneous jargon isn't helping your argument.
As a last approach try the plywood hands on method I suggested near the beginning. It can be overpowering.

I think I've done about all I can to illustrate it for you.

 

Working from bottom to top. Your daughter should have stayed for the rest of the class before she explained per cent to you. You are missing the per part. .007" is .7% of, wait for it, 1". One inch of what? Where did the 1" come from. .007" is 50% of .014". 700 people is .7% of what? So? It's no wonder we're not getting anywhere with this.

The movement in the drawing is the only thing you are changing, that's right, the only variable. But unless you compare it to the other moving pieces you are not going anywhere with that.

A vertical stick the length of the distance between the outer u-joint and the outer strut pivot, whatever that is. Let's say it's 5 inches. Doesn't matter. The top of the stick moves over to the right .144". The bottom moves over .144" to the right. How much is the stick leaning now (camber)? None. Still vertical. This is what would happen if top and bottom arms were the same lengths.

2nd case, the top of the stick moves over .144" to the right. Now you move the bottom of the stick over .120". How much is the stick leaning now? The top of the stick is leaning over .024" to the right. We have camber change.
Now these dimensions, .144 and .120 are the actual amounts, calculated geometrically that a 14" radius and a 16.750 radius travel horizontally when moved 2" vertically from horizontal. These are not made up.

3rd case top of the stick still moves over .144 to the right, bottom of the stick moves over .124 to the right. How much is the stick leaning now. The top of the stick is leaning over .020. The .124 is the calculated horizontal movement of the arc with a radius of 16.250".

Now all these numbers are very small, but that's all it takes. That's what the design entailed. The oe design wanted that .024" lean and by lengthening the rod you have changed that to .020. Yes, .004 is a very small amount, but it is 1/6th of the previous travel. One sixth of something is not huge, but it is significant.
(BTW to convert 1/6 to a percentage divide the top number by the bottom and multiply by 100. It is a comparison of the top number to the bottom.) 1 divided by 6 = .16666666... multiplied by 100 is 16.666...%, rounded up to 17%.

As I said before 17% is not small change.

The design "lean" is about .024,



Rather than try to explain this further I will do some drawings for you using a high school geometry set and illustrate what's wrong with your drawings and your logic.

Steve g

 

You can't be serious about this stuff....
My daughter can obviously teach you some basic math.

The top of blue arc has a value of '0'
The top of the red arc swings a value of '.007" (further distance).

The difference between the 2 arc points is .007"

.007 or 7/1000 x 100 = 0.7%

The arc points have changed by 0.7%

Other examples;
Either convert the decimals to fractions and multiply by 100 or move the decimal points.
Plug in any numbers you want.

.40 or 2/5 x 100 = 40%

.60 or 6/100 or 3/50 x 100 = 60%

Basic grade 5 and 6 stuff.

 

Steve, I've seen enough of your



Welcome to my ignore list.


edit - And, FWIW, you were the one who crashed my CV thread by hijacking it to "teach" your short sighted suspension theory, much as you've done here. As for my posts here regarding camber curves, your misinformation made them somewhat necessary, so that other viewers might have a better understanding of the facts on which they should base any relevant decisions.

 

Come on Noonie, get a grip here. A percentage is a description of a portion of something. .004 is a portion of .024. How big a part is .004 of .024? .024 is 100% of .024. .004" is 16.666% of .024"

When you talk about a percentage it is a percentage of something. When you have 100 % of something, you have all of it. When do you ever hear someone say 40% of some unknown number. How can that be? 60 mph is 600%. What does that mean. Well that's exactly what you're saying when you say .007 is 7%. Get your daughter to explain the arithmatic to you. .007" is .7% of 1.000". There is no other answer for that. Now where did the 1.000" come from?


If you want to quote a percentage you need to identify what it is a percentage of, otherwise it's meaningless.

Can I do your taxes for you?

Steve g

 

Thank you.