I'm building a 6-link rear while I'm doing my frame off. Anybody got pics of their 6-link mods? It's suppose to handle a lot better. I'll be putting a lot of HP to it so I thought I should modify it a little. Got pics of the progress if anybody is interested.

 

Yes please post them. There are others who've done this, Norval being one. Search the archives and you find them.

 

A 6 link does NOTHING for handling that a well set-up properly maintained stock system doesn't. It just eliminates the halfshaft as a suspension geometry member, if you have a tight diff w/ no stub axle play it will not improve anything. The biggest advantage is that if you snap a halfshaft and the halfshaft doesn't take out the 6 link and/or camber rods you won't loose the rear suspension corner

 

When you take off at the line, your stock suspension dives, upon diving the geometry of the stock suspension turns the wheels in(large camber change) as most vette owners have seen. With the 6-link mod the wheels have less camber change than the stock setup. Hence more tread contact with the road meaning more traction.The same goes for handling in corners.

 

If this is your major concern you could lower the inboard strut rod pivot points and fit a stiffer spring to accomlish the same thing,
it be a lot less work.

 

That's just how you design the system, you can also simply change the camber curve by modifying the lower camber bracket. Also, camber change is a good thing, unless you are only going in a straight line. Less camber change with a car that does NOT have reduced roll stiffness means less tire contact with the road, a smaller slip angle and easier loss of traction...in other words, the car won't corner as well.

i would advise you educate yourself some more on suspension geometry. Building a parallel rod setup 6 link with NOT camber change is perhaps not the best thing to do if you want the car to handle better. Trains don't have a camber curve

When you take off the rear suspension squats, you can't build in 100% (or more) anti squat in an IRS because the diff is unsprung, that's one of the biggest IRS downsides. You can get maybe 50% or so realisticly but with the stock strailing arm setup you can't change it, a double forward link w/ a virtual center like the C4 allows you to change the virtual swing arm...if you want to modify the brackets and links (much like a 4 link live axle usually has multiple holes for the rods to adjust this virtual arm and with it anti squat or pro squat) Anti or pro dive is something you see on the front suspension.

 

I am lowering the lower strut rod with the Vette Brakes bracket. I'm fabricating an upper bracket to go on the top of the diff and the trailing arms. I'm using Bicknell Racing rods and heim joints for the rods. I really don't understand your reasoning for no improvement in handling given that Corvette Fever did an article on this setup and improved their skid pad numbers from I beleive .82g's to .92g's, or are they lying. They mentioned that with better tires they could attain 1g....try that with stock suspension. So I think I'm going to ignore your "stupid" comment and go with the people who have knowledge on the subject.

 

Uh-oh......here we go again

 

Lol

 

yeah..I make stupid comments..I know **** about this stuff...

A 6 link in itself says nothing about camber changes, it's the geometry that does, so even if you stick a pair upper control rods in your IRS that doesn't mean it's the same as the corvette fever one, what geometry did they have, what initial camber setting, how roll resistant was their car???
If you knew ANYTHING about the stock IRS you'd know that toe control is the problem, not camber control.

Oh and Corvette Fever.. yaeh, a rael engineering mag there..no advertising based comment there eh? i suggest you read a REAL magazine on suspension and other high tech stuff...get yourself a Race Car Engineering subscription.

 

Tell me what I should do.

 

read some books, educate yourself, study the car, measure and then design something that will work, or just settle for a camber curve that comes with aftermarket componenets (read an aftermarket lower camber bracket) and build the upper rods to compliment the geometry of the lowers so you retain the same instantaneous cetner and geometry that is shared by the lower rods and the halfshaft, this will keep the camber curve the same and will make that the stuv axle doesn't move in and out of the diff and excessive amount, the closer you get it the less the stub will move. Lining up the pivots and adjusting the rod angles is critical here.

 

TT is right on this one. In simple terms, you WANT camber gain in roll so the tire stays upright when cornering, this offsets the effect of body roll. Drag racing is a different animal. If cornering is of no concern, then you may want to keep the tire vertical throughout its travel, ie so the tire stays upright under squat - just be prepared for a lot of oversteer in corners.

IMO, the trick setup would be to remove the t-arms and copy a C4 set up with four forward links and a toe control rod.

And yes, the real problem is toe control.

 

I'm NOT cobbling this thing together. True independent rear suspension has an upper and lower control arm.....NOT ONE....and when you look, the lower strut rod is not parallel with the driveshaft which is an issue. Another is that the driveshaft is part of the suspension, the upper strut rod eliminates the driveshatft out of the suspension. I've seen many diff yokes worn(inside the diff) because of pressure put on the yoke from the suspension. As wear precipitates the handling gets worse , not to mention the excess metal in the rear end. Another reason for this mod.

 

the stock susp. does have an upper control arm, the halfshaft and it does an adequate job. The only major difference is the stub axle play but otherwise it's a cost efficient deisgn since it saves on parts and is always dead on since the halfshaft and lower rod always hae the same instantaneous center..since the halfshaft is itself determining that.

If you want to do it to address the wear issue then that's a great idea, building it is relativly easy then, just do what I said above w/ the rod angles and pivot points.

 

Just so I understand it correctly..please.

 

Toe control is done by the trailing arm and half shaft/ camber rod arrangement. You know what TOE is right?



There is no true toe control in our IRS, the toe is set by the trailing arm front bushing (shims on both sides) and the toe then changes over susp. travel, which uis a bad thing. This change is due to the trailing arm desing. Being "fixed" in the frame the front mount doesn't move, however when the susp. moves the hub moves in and outboard as the halfshaft and control rod angle away from horizontal, this effectively changes their horizontal component. This in return changes the angle that the trailing arm makes with the car centerline. A c4 suspension has 2 forward trailing rods that hinge at the frame mount and at the hub, this way they offer no influence on the toe, the hub hinges freely. They have a toe control rod on the back of the hub (connected to center of diff) to handle that. This is vastly superior to what we have even though the C4 system uses long rods moutned in the center to reduce angular effect, the ebst system has pivots in line with the u joints and rods parallel w/ the halfshaft and just as long so it's a "parallelogram" which fixes the toe, so it remains the same throughout travel. Another advantage of the trailing rods is that, like I said above, they allow you to customize the virtual swing arm and with that affect hub fiore/aftmovement, yaw and more importantly anti squat.

 

this pic illustrates the problem, see the dotted line from the spindle centerline? that's the toe right there (well actually axis perpendicular to toe)


now imagine this moving up and down and the halfshaft angling, it'll become "shorter" in this plane, the hub will move inboard and the toe will change

This in/outboard movement is also what keeps the suspension jacked up after setting the susp back on the ground, the tires keep the hib from moving sideways and therefore the halfshaft remains angled and the car "jacked up"

 

How hard would it to be to develop a system such as the c4's to correct the toe problem on a c3.

 

now compare it to this:

That's a C4 type system right there. Only the left has a toe control rod in this pic