[lsejlowe]

well, suspension threads seems to be a dime a dozen around here any more, so I thought I'd add another :laughing:

I'm planning on making some HD struts already, but figure I should make a new bracket while I'm at it to make the most of my improvements. After reading through this 5-link thread it's clear that having the ends of the rods vertically in line with the U-joints will create a parallelogram between the halfshaft and strut rod and thereby will eliminate camber change through suspension travel. However, without modifying the bearing housing on the TA the outer end is fixed.

What is the ideal location (relative to stock) of the inner rod mount to minimize camber change with an otherwise stock suspension?

Here are some very helpful solid models I copied from the 5-link thread:

I am still having trouble trying to decide what the amount of camber gain should be over 2 in of suspension travel. For reference here is a stock corvette

And a Smart strut setup. I have droped the strut mount 1-1/2" down.

looks like lowering it 1.5" helps a lot, but shouldn't it move outboard slightly as well?

 

[yellow73sb]

The desired stager for the inner and out heights from the ground is an 1 1/4 with the inner mounts being the highest.

The smart strut is not necessary

Check out corvettefaq.com and read some of Herb Adams and other corvette masters' paper's.

Edit: specifically this massive file

http://www.corvettefaq.com/c3/CorvetteHandling.pdf

I would recommend saving it to your computer so you don't have to download every time you want to read it. Or better yet print it out.

 

[lsejlowe]

The desired stager for the inner and out heights from the ground is an 1 1/4 with the inner mounts being the highest.

I'm a little unclear what you mean here. Clarification?

 

[yellow73sb]

Read the .pdf file. I believe he refers to it as the "z" height

 

[lsejlowe]

hmm, saw no reference to "z-height" or design of the strut bracket. Just saw stuff about the use of rod ends rather than bushings. :huh:

 

[yellow73sb]

I could have sworn it was that article.

I know it was a herb adams article.

I have them all saved on my old computer

 

[84rzv500r]

I completed my 6 link over the weekend. I have a parallel uneven length setup with telescoping half shafts and the links parallel to the ground at normal ride height. This places the instantaneous center at infinity (the links are parallel) and the roll center at ground level. I agonized a bit over the upper link placement and built a kinematic model and in the end (with some discussion with TT) decided that placing the inner pivots in a line through the center of the inner ujoint was the way to go. I have allowed for a later upgrade to include floating trailing arm pivots and toe control rods.

I will measure the camber (my eyeball engineering says not much camber change) and toe change (should be Very similar to stock) through the practical limits of travel (about +-2 inches)

I run 550 springs and a 7/8"? sway bar in the front and a custom Guldstrand 7 leaf in the rear with NO bar. The car is fairly light with aftermarket bodywork, no bumpers, lightweight wheels tires, brakes, seats, steering column, dash ect...

I have not had the new setup on the road yet but VERY VERY Soon :thumbsup: :thumbsup: :devil:

Before the 6 link the rear suspension at full droop went way positive camber.

I boxed in the stock bracket...

 

[BBShark]

Jason, I sent you a basic DXF of the rear suspension. You should be able to determine an optimal location from that.

 

[big2bird]

The desired stager for the inner and out heights from the ground is an 1 1/4 with the inner mounts being the highest.

The smart strut is not necessary

Check out corvettefaq.com and read some of Herb Adams and other corvette masters' paper's.

Edit: specifically this massive file

http://www.corvettefaq.com/c3/CorvetteHandling.pdf

I would recommend saving it to your computer so you don't have to download every time you want to read it. Or better yet print it out.

Thanks for that link. Got lot's of good reading to do now.

 

[Strider]

hmm, saw no reference to "z-height" or design of the strut bracket. Just saw stuff about the use of rod ends rather than bushings. :huh:

They talk about the "Z-height in the Chevy power manual. they also talk about bull dozing springs to correct this "Z" height

 

[Strider]

I would like to see a picture of your top inner mount?
This is mine and I believe you did it the same way?

 

[84rzv500r]

I would like to see a picture of your top inner mount?
This is mine and I believe you did it the same way?

Yes, that's essentially what I did. I used a piece of 1"x0.250 Wall A513 DOM tube tapped 5/8-18 welded to what amounts ot a large 3/16 thick washer to spread the load and gusseted with 1/8 and 3/16 gussets back to the tube. This assembly was welded to the differential cross member that I had already reinforced and rewelded.

The upper inner mount is in a line connecting the center of the upper mount, the center of the ujoint, and the center of the lower mount that was lowered about 1.5" this brings all three elements the upper an lower strut rods and the halfshafts parallel and in the same vertical plane (more or less).

I'll get a picture for you in a day or so.

:thumbsup:

 

[yellow73sb]

So does the smart strut bracket raise the roll center?

 

[turtlevette]

the first picture was the more desireable condition. When the car rolls in the turn camber must be more negative for a good footprint.

 

[yellow73sb]

Oh I didn't even look at that.

I also didn't realize that the smart strut bracket moves it down 1.5"

Herb adams recommended it to be moved down .5"

I'll be putting my stock bracket on after I brace it

 

[BBShark]

the first picture was the more desireable condition. When the car rolls in the turn camber must be more negative for a good footprint.

People show these camber measurements as if the body of the car is completely flat (0 degree roll) and the outer wheel is in compression 2 inches. For that to be true, the other (inside) wheel would also be in compression 2 inches. We all know this does not happen.

If the body rolls 2 degrees (2 inch compression of the outside wheel), this coincidentally adds up to ~2 degrees! So, I have to agree, that will maximize your footprint.

 

[lsejlowe]

People show these camber measurements as if the body of the car is completely flat (0 degree roll) and the outer wheel is in compression 2 inches. For that to be true, the other (inside) wheel would also be in compression 2 inches. We all know this does not happen.

If the body rolls 2 degrees (2 inch compression of the outside wheel), this coincidentally adds up to ~2 degrees! So, I have to agree, that will maximize your footprint.

out of curiosity, how did you get from 2* of body roll to 2 inch compression of outside wheel? I just did a quick geometric solution with a total width of 69" and with 2* of roll figured it to be about 1.2" of compression:

compression = total width/2 * tan(body roll) = 34.5 * 0.0349 = 1.205

is there a proper method for calculating it?

 

[turtlevette]

out of curiosity, how did you get from 2* of body roll to 2 inch compression of outside wheel? I just did a quick geometric solution with a total width of 69" and with 2* of roll figured it to be about 1.2" of compression:

compression = total width/2 * tan(body roll) = 34.5 * 0.0349 = 1.205

is there a proper method for calculating it?

i'm thinking it's the sin function but it works out the same.

further proving these brackets are for drag racing purposes only.

I bet the pict below is more than 2 deg. I bet more like 5 or 6.

 

[TwinTurbo]

The bracket is not just for drag racing, however the reduction in camber gain is a bit much, especially on a stockish car. The stock camber curve is a little bit on the high side but more importantly, the geometry has a too high roll center and therefore a jacking effect. Lowering the inner pivots lowers the roll center, which is a good thing. However, since it also reduces the camber gain you always want to conbine this with making your car more roll resistant/stiff. This should be the 1st goal, getting the car to roll as little as p;ossible and then you can lower the roll center to eliminate jacking and alter the camber curvle. The jacking problem is also there because you're stuck with the halfhsaft as the upper member, the lower rod is the only variable you have to alter the camber characterstics, a 6 link can change that however you'd need telescopic shafts, otherwise you'd end up with something that has to work with the stock shaft in place but floated, to eliminate excessive stub movement you really can't change anything radical unless you cahnge both rods at the same time and keep the IC in compliance with the halfshaft (or close)
Of course, when you significantly lower the car that lowers the roll center also, lower it a lot (slammed) and the differential position comes into play, positive toe changes and all that. It's compromises all over the board. I do agree that the smart strut bracket lowers the pivots way too much, especially since most of these cars roll more than the camber gain those give (they do still allow camber gain as the halfhsaft is still shorter giving a trapezoid, only if the rods are equal length to the halfshaft will it give a parallellogramme)
I really don't understand why turtles car is still listing like the andrea doria, what kind of sway bars do you have, what springs, I think you lowered the car?

 

[turtlevette]

I really don't understand why turtles car is still listing like the andrea doria, what kind of sway bars do you have, what springs, I think you lowered the car?

We've been through it a 100 times. 550/420 1.125 bar heavy shocks. It probably just comes down to the fact that i push the car more than most.

We just don't have many really good picts of C3 on a track. The white one (Jason Staley) look like it was leaning pretty good too. He's still learning though and will probably get it to lean more as he pushes it harder.

The only time mine has jacked is in hard low speed turns on the street or autocross. It sits down pretty nice on the road course. The guy behind me is a raced prepped car probably with 1200# springs.