behardt91

I'm thinking about building my own 6 link in the future because of the clear advantages over the stock rear suspension setup. I'm basically going to do like the dragvette setup and use equal length/parellel upper and lower adjustable strut rods. I know some people have done this. Where is a good place to get some custom length strut rods for a good price?

TheSkunkWorks

I might suggest you take the time to do some serious homework in vehicle dynamics before engineering your own rear suspension geometry. Equal length parallel links may be the ticket for drag racing, but do anything other than driving in straight lines and the "advantages" of such a system vanish immediately, as positive (and I don't mean in a good way) camber gain equal to the amount your chassis rolls in turns will occur.

TSW

behardt91

Well most of my actual racing is just for fun at the local drag strip. But in the case of track racing, which I haven't done, i understand cars need to be setup for proper camber gain. So I could design the system to increase negative camber when the outer wheel experiences jounce on a turn but for drag racing that isn't necessary. Am I correct?

Solid LT1

Speedway Motors has 5/8" and 3/4" treaded links in various lengths. Good place to price rod ends too.

TheSkunkWorks

Yes, ideally you don't want camber gain in either direction for drag racing. However, for any other type of driving, tracking or not, it is typically desirable to have an amount of negative camber gain, tho many factors dictate the optimum amount. If you don't wish to do a lot of head scratching here, I recommend at least designing in an alternate linkage arrangement which provides a similar camber gain curve as would simply lowering the inner camber strut links ~1/2" below C3 stock height (relative to the diff) on an OE layout as being a good default setup when away from the strip. Sorry, regardless of claims you may read there just isn't a one-size-fits-all setup for every car which works equally well at the strip and everywhere else; one and/or the other will necessarily be compromised.

Also, be aware that adding upper linkages above the half-shafts may well present clearance issues in full bump or jounce. You wouldn't be the first to run into that one.

If you go back and forth very often, I'd think also think about getting adjstable shocks. If you get serious about carving corners, Aurora or NMB rod ends come highly recommended, and I'd stay away from any with zerks regardless.

behardt91

So let's assume I build a 6 link and I modify the strut bracket below the diff to have 2 possible mounting holes on each side for adjustable struts. One of the holes would make the lower link parellel to the halfshaft and top link like the dragvette setup. The second hole would be right above, positioning the lower link say 1/2 inch below the stock location, and taking away the parallel situation. So if I mounted the link in the upper hole, in theory would the wheel increase camber during jounce/rebound?

I'm also under the assumption you can adjust toe more easily using a 6 link by lengthening/shortening both links by the same amount. That's why I'm curious. BTW, a five bar system or lightly modified stock setup isn't out of the question. I'm just trying to increase my understanding of things.

Belgian1979vette

It has been done and the plans are free.

Steve2147

The point in long arm/short arm parallel link suspension is not primarily about camber angle. That's more a coincidental. The design was created to reduce tire scrub from track change.

The problem with equel length links is that as a control arm goes through it's range of travel the outer end moves in an arc, with the control arm the radius of the arc. As such, as it moves in the arc it moves closer to the centre line of the vehicle. Equel length arms travel in identical arcs and as the suspension moves the tire scrubs across the road moving toward the centre of the vehicle. Of course this is not good for tire wear or vehicle stability as you are breaking the tire loose to do it.

By having the upper control arm shorter the outer pivot point travels in a tighter arc. which means for the same amount of vertical travel it move further towards the centreline of the vehicle than the lower outer pivot point. Because the top is moving in more than the bottom the tire "rocks" outward at the bottom, pivoting on the lower pivot point. The difference in the lengths of the two arms is calculated so that the rocking outward effect is equal to the inward horizontal travel of the arc so that the tire stays put in it's track.

The camber change is not ideal. Keeping the tire perpendicular to the ground would be better, the ideal would be to have camber move slightly to the neg when the suspension is in a compressed state and move slightly towards positive in it's elongated position. Because the tire leans neg on turns in both directions you are not getting any aid in stability from one tire in a corner (one is always leaning the wrong way in relation to the turn). The camber change was accepted as collateral damage in exchange for maintaining track distance and reducing unsprung weight.

Steve g

RobbSalzmann

Any links? I've searched, but seem to come up with bubkus.

MrForce

PM sent

DaveL82

Going with a 6 link allows you to remove the half shaft as the upper link. All half shafts have some play as the yoke moves in and out of the diff and over time this gets worse.

The stock lower link location on the diff can give up to 2.5 to 3 degrees of camber gain using the stock half shaft as the upper link. With modern wide wheels and tires I try to keep that to 1.5 to 2 degrees of camber gain by lowering the diff mount.

Even if you do this mod you still can't control toe change as the hub moves in and out due to the two suspension links traveling up and down and the t-arm bolted to a stationary point on the frame.

The best low cost approach is to stiffen the suspension to reduce movement of the suspension therefore reducing camber and toe changes but this doesn't work for a drag car as you need softer suspension for weight transfer. This type of IRS is not good for drag racing as everything is a compromise.

I use my car for roadrace track days so I built a double arm system. This was a lot of work and not sure I'd do it again but now real satisfied with result.

voidhead1

This should get you started: http://www.corvettefaq.com/c3/6link/index.html

Good luck ...

behardt91

That article is actually the reason I started thinking about doing a 6 link. It is very convincing especially when they talk to you about the lateral g's of the 6 link car vs the stock car. I dont know what to believe though. I just need to keep researching i suppose.

Steve2147

That article shows an unequel arm parallel system. It's action pretty much mirrors the geometry of the original system. Pay particular attention to how they determined the length for the upper arm, drawing a line through the end of the outer u-joint. Read this little piece under the section that starts "short arm/long arm", in particular just below the control arm bushings illustration.

http://www.monroe.com.au/trade-corne...spensions.html

Running an equel length system will keep the tire flat on the ground, but will move it inward quite a bit when the car squats down when you launch. I don't know how much of an issue it will be in the traction end, but it can't be good. But more importantly it is not good when you're driving around town and the suspension is moving all the time. A 16" strut travels in a small enough arc that 5" of travel from horizontal will be significant.

Steve g

TheSkunkWorks

With the exception of underpowered vehicles, minimizing rear tire scrub or track changes are of secondary importance relative to keeping them squarely planted during acceleration in order to maintain maximum footprint, whether launching at the strip or exiting turns. As I stated earlier, the optimum camber gain (or lack of it) necessary to accomplish this varies...

68 NJConv 454

Zychron

The Giovanni system is not a 6 link. The C4 style plan is covered in this thread. I think a couple of people have done it from the plans.

http://www.vettemod.com/forum/showthread.php?t=3126