OK, here's what I've got up to this point. I think the animation will explain itself, as you can clearly see how the wishbones move, and how the movement affects the position of the spider.



See how the spider moves IN as the suspension goes UP or DOWN from center.

You can download the images used to make the animation (to see the details better) using the links below.

Figure 1
Figure 2
Figure 3

 

So let me take a stab at this.... according to your drawing the "best" time to use spacers (if you were going to use them) would be if your axle sat straight at ride height?

 

man...wtf is going on???

 

Was there pages deleted since on the first page you mention page 8?

 

Actually, it would be the wishbones that needed to be straight. The angle of the wishbones determines how far the outer CV joint is from the differential, and that's what determines how far the spider will be sitting in the cup. If you raise an S2000 slightly the arms will be level, so at static ride height the spider would be out as far as it ever will be, and to get it back where it was (at static ride height) you could move the cup out slightly using thin spacers. If there would be any benefit to this I can't see what it would be.

BTW, the "drawing" is actually a mathematical construction, so it shows what it shows with mathematical certainty.

I find it interesting that once we see how the spider really moves with suspension movement, it bocomes instantly clear why the spacers have eleminated the vibrations some owners have experienced after lowering. If there is wear (pitting) in the cup before the car is lowered, the slight angle change of the half shaft and slightly different position in the cup leaves the balls repeatedly running in and out of the old pits, creating vibration. The spacers push the cups out, setting the spider even deeper in the cup, so that it is now running on an unworn area of the cup. The proper fix of course would be to either replace the worn cups or maybe swap them side to side. Billman is far more qualified than me to comment on what would be the correct fix for this kind of vibration, but using spacers to run the spider deeper in the cup where there is no wear is a bandaid rather than a fix for the real problem.
I guess page numbering may vary depending on browser or forum settings. I'm showing 11 pages right now, and as far as I'm aware, no pages have been deleted. For me, page 8 is three pages back from your post.
Read the thread.

I'd offer to draw you a picture, but I already did.
(We're still waiting for measurements from Bill, but the animation and drawing show what we can expect. I'm sure I'm not the only one eager to hear from Billman and SpitfireS. )

 

^
can you sum it up so that it is easy for me to understand?

i don't follow your picture or explanations...

if you don't mind...and it doesn't seem like you would...you type a lot

 

This is a (hand made ) scale drawing of the rear suspension and chassis.
Black = chassis measurements (as good as I could)
Red = suspension compressed.
Blue = suspension with wheels of the ground.
All measurements are in mm.
Axle lenght in drawing is not to scale.
It doesn't matter, IMO it does show the axle is pulled out of the CV bucket a bit when the suspension is compressed.
Look at the negative camber when the suspension is compressed.
When you adjust it to back to "oem" spec in that compressed position, you may pull the axle back in because you adjust camber at the lower arm (making it shorter).

Measurements that Billman is going to make will be better.
Moving a suspension up & down without a shock will give the best proof spacers are not needed IMO.
I'm looking forward seeing Billmans measurements.
(to see how I did)


I did not do this just for this topic.
There is some high pitched buzzz coming from the trans and I wanted to find out where it came from.
So I jacked up the rear, removed the wheels and crawled underneath.
It looks like sec reduction gear or bearings....

The other drawing was made in MS Paint.
I don't have the skills to make anything in AutoCad.
That's how old I allready am
Polytechnic school didn't have autocad when I was there, 1 or 2 years after that they did.

 

SpitfireS, of course as you go from extension to compression, as your drawing shows, and the compression is less than the extension, then the balls will be further in during extension. My animation shows that too.

Relative to full wishbone extension (arms as level as possible) the spider is as far out as it will ever be. Simple geometry shows this (as in the animation).

I'm working on a 25 frame animation that shows the geometry that is involved more clearly (for those who can't see what's happening with the simpler amination). I'll probably have to post a link to it becaues it will probably be too big to embed in a forum post. More to come.

(As an aside, I sure do wish the math/geometry beyhind this was more obvious to everyone. )

 

I'll try, but FWIW, I'm trying to cut down on the amount of time I spend posting on S2kI.
Here's an improved animation that will help with the explinations that follow.



You can view the full size images used to create the animation here.

Please understand that this is primarily a lesson in geometry, and spicifically the geometry of a suspension system that uses unequal length wishbones and half shafts. The S2000 has this type of setup, so the same principles will apply, but the concepts are general and apply to any such system. The animation shows the upper wishbone as being shorter than the lower one, and the shaft as being longer than either, as is the case with the S2000, but the same movements will take place as long as both the wishbones are shorter than the shaft.

Now I'll try to describe the various parts of the animation just in case it's not clear to everyone.

Points A and C are the pivot points for the arms. Points B and D represent the ends of the two arms. Line segment AB represents the upper arm, and line segment CD represents the lower arm. Point E is the mid point of a line between point B and point D, and represents the outer CV joint. Keep in mind that this is not a particular car being represented, but just an animation showing how the geometry works out.

As the arms move up and down, the outer CV joint (point E) remains centered between them, just as it does on a real world suspension system. The verticle dashed line that waggs back and forth shows the camber change that takes place becuase the arms are of different length.

Now look at the upper arm. See the dashed circle that has the pivot point of the arm at it's center and the end of the arm riding on the perimeter? Since the arm is a fixed length, this is the circle the end would enscribe if it could be rotated through a full 360 degrees. IOW, the end of the arm will always be on the perimeter of the dashed circle. The same is true of the larger circle around the lower arm. Notice how the ends of the arms always follow the perimeter of the circles?
(The circles wobble a little due to round off error, and would not do this if I'd used greater precision. The wobble doesn't have any significant effect on the results, but it might look odd if you don't understand the source. )

Also notice that there are two counters near the pivot points of the two arms. These counters are showing the changing angle of the arms. Notice that for a given amount of movement up or down, the angle of the longer arm changes less than the angle of the shorter arm. This is why the camber changes, and it happens because the shorter arm moves the top of the wheel inward quicker than the longer lower arm.

Now lets look at the shaft, which is represented by line segment FE. We already know from looking at the arms that the shaft angle is going to change slower than the arm angles, because it's longer. The counter near the left side of the shaft shows the angle of the shaft as it changes with suspension movement. Also notice that there are three blue numbers on the animation. These numbers represent the physical length of the arms and shaft, and would be changing if any of the lengths were changing. Of course they're not changing, and they shouldn't be changing, so it's all good.

The shaft is a fixed length, and affixed to the outer CV joint (point E) and must move in and out, as well as up and down, with the suspension movement. The inside of the shaft (point F) represents the spider in the inner CV joint, and it plunges straight back and forth along the line it is resting on, so that line represents the plane of the CV joint bucket, and the movement of point F shows how the spider plunges in and out of the bucket as the suspension moves.

Now for some observations. Please look at the animation if it helps make this clearer. First, when the arms are pointed outward-most, the shaft, the spider will be pulled out as far as it can be pulled. This will be true no matter how the arms and shaft are angled relative to each other, and no matter what their relative length, as long as the shaft is longer than both the arms. Also, note that when the animation shows the suspension with the wishbone angles most mearly matching SpitfireS's drawing, the spider is in the same relative position. Hopefully the finer steps of the latest animation will make it clear that this is just basic geometry and will always work out the same way. Notice also that the spider hardly moves at all until the arm angles become significant. Those who aren't convinced will just have to wait for measurements from Billman and scale drawings from SpitfireS, but those who can grasp the geometric relationships won't have to wait.

Hope this is a sufficient and not too too long explination.

Oh yea, as for the spider moving in our out when you change the ride height, it all depends where you start out, but anywhere near level the changes in spider position are minimal (as you can clearly see in the animation). Billman's measurements will show this, as actual suspension movement is limited and the spider movement with an inch of suspension movement is going to be small. If that's not obvious from watching the animation and understanding the geometry that's involved, then you'll just have to wait for Bill.

 

Nice animation
Geometry doesn't lie
But.. the suspension doesn't look like the drawing.
Upper arm is about half of the lower arm lenght and further out.
Axle isn't in the middle of the hub.
The hub is longer - longer then the upper arm.

DrGeo doesn't run on Windows...
I've made a couple 1:2.5 scale drawings (old fashion way - on paper) and I was surpriced to see the axle doesn't move that much.
Positions were: lowest, lower arm straight, upper arm straight, highest and some in between.
In all drawings the axle stays within 1 mm (2.5 mm in real dimentions) of its "original" point.
IMO the Honda suspension engineers did a fine job in keeping the spider at its place.

If possible make a scale animation of the S2000 suspension.
You'll be surpriced