Renderings by Filip Trojanek
Here's the thing about solid-axle rear suspensions; fancy parts and exotic housings designed for track use aren't much good if we're not getting it to the ground. Hooking ain't just for drag racers; the quicker and harder we can get back on the throttle when exiting a corner, the harder we can accelerate and the faster our lap times will be. That's a consideration that becomes increasingly important as horsepower and torque levels rise, and with what we've got in store for project Max Effort, we knew we needed to do our homework.
While torque-arm rear suspensions in general are great at transferring power and controlling axle rotation, there's more to it than just bolting one on-lower control arm angle and torque arm length both have a direct impact on forward bite. There's no single perfect setup that's best for all conditions, since vehicle specifics and track conditions vary (wet, dusty, temperature), but they can be overcome by fine-tuning, provided you've got the ability to adjust. There may be times when more forward bite trumps perfect roll geometry and makes the car much faster. Other times the track surface will be ideal, so emphasis can be redirected to optimize roll geometry to increase lap times. What's important is the ability to deal with changing conditions, and understanding how the adjustments affect the car.
For a torque arm suspension, the instant center is located on a vertical
To cope with all those variables, Max's rear suspension system is getting the upgrade to CorteX Racing's Ultimate LCAs that are designed to allow quick and accurate geometry adjustments that will dramatically alter the performance. To minimize the roll oversteer, our LCAs are growing several inches in length. Why? Long LCAs are beneficial because for a given change in height of either end of the arm, the angularity changes less than with a short arm. This keeps the suspension geometry more optimal in bump and roll modes.
As far as the considerations on the chassis, the main variables we're concerned with are center of gravity (CG), height, tires, wheelbase, driving style, and track condition. By using a properly designed torque arm rear suspension system it's possible to set up a car with between 60 and 100 percent antisquat and still achieve excellent roll-steer characteristics. That means we can theoretically create a rear suspension with the best of all worlds: amazing turn-in, high mid-corner grip, and also exceptional bite when exiting a corner, allowing the driver to get on the throttle hard and early. Get all that right and lap times drop radically.
For reference, these are the standard CorteX Racing LCAs we used during the rear suspensio
As viewed from the side, the upgraded CorteX Racing Ultimate LCAs allow a great deal of an
The assumption in getting the exact value of antisquat is the center of gravity (CG) of th
Here's Ryan Kertz's sketch of our plan of attack on Max Effort. This LCA design is a sligh
To begin, Kertz took chassis measurements to determine the race height for the rear suspen
To get the length and geometry we need, neither the subframe mount nor leaf-spring pocket
With the floor removed, it's now easy to see how much room we have to work with without al
To create our mounting point, Kertz welds in a flat 3/8-inch plate for the floor of the to
To create the longer LCAs, Kertz disassembled our previous short ones to reuse the rod end
With the LCA tacked together, the next step was to create the pocket that will capture our
Here it is tacked into place; now we've got a far stronger mounting point for our LCAs as
Here's the completed LCA. Note that now we've got a great deal of adjustability on both en
Remember that hole in the torque box floor from earlier? It extends all the way through th
On this end of the LCA, adjustment will be as easy as rearranging this stack of spacers. A
|CENTER OF GRAVITY = 18 INCHES