Originally Posted by PTAddict (Post 31894)

Here are a few basics to keep in mind as you do your reading :)

Roll Center Height: If you have one pair of angled links, the roll center height will be located at the virtual intersection of the two angled links. From a practical standpoint, with this design, you want to get this as low as possible. The Morrison designs put the upper, angled links at the height of the axle housing, which is better than most such designs which put brackets on top of the housing (unacceptable, IMO). Even better, as suggested by Herb Adams, is to make the lower links the angled pair, but this is more difficult to pull off from a structural and packaging standpoint.

Side View Swing Arm and Roll Steer: Viewing the suspension from the side, imagine extending the upper and lower links until they intersect in space. The line from this point to the center of the axle is the SVSA. The angle that this SVSA forms with the roll axis is important, because it determines whether you will have roll understeer, oversteer, neutral steer. If the SVSA is angled upward toward the front, you will have roll oversteer, which will make your car unpredictable and twitchy on turn-in. Some amount of roll understeer is generally considered desireable, but there are tradeoffs between achieving this and keeping the instant center higher to get more anti-squat. Also, keep in mind that the shorter the SVSA is, the more likely you are to suffer from brake hop.

Instant Center and Anti-Squat: The intersection of the upper and lower links in the side view, as described above, is the instant center. Draw a line from the point of the rear contact patch through this instant center, and find the intersection point with a horizontal line at the height of the center of gravity of the car. If this intersection point occurs forward of the front contact patch, you have less than 100% anti-squat, if it occurs between the contact patches, you have more than 100% anti-squat. Some amount of anti-squat is desirable, to help the car hook up on acceleration out of the corners. Just how much you want is debated, but if you can get close to 100% AS while still having roll understeer, you're doing pretty well.

Link Length: The shorter the links are, the more all of these parameters will change as the suspension moves, and the greater the chance that the suspension will start to bind up to a significant degree. From a practical standpoint, it's hard to have links that are too long.

Getting the optimum balance of all these parameters - even knowing what the optimum balance is, and what it feels like to the driver - is what makes suspension design hard. Build some adjustability in, for sure.

Originally Posted by wedged (Post 323530)

"The Jim Meyer Racing Products adjustable low-roll-center Panhard bar, that mounts behind the rear axle housing, is also parallel with the centerline of the housing "