In the last installment of Project Corolla, we dialed in a set of custom Ground Control coilovers, then figured out spring rates and ride height adjustments to make the suspension work on the track. We chose 6kg/mm springs in front, in conjunction with specially valved Koni twin-tube dampers and 4kg/mm rear springs, mounted on monotube shocks. While we've had some issues with the overall amount of suspension stroke, we've made the setup acceptable-for the time being.
Roll, Squat And Bind
One trend among tuned Corollas is the tendency to lower them by too much. Even with spring rates sufficiently high to enable proper suspension function with such a short stroke, there are severe alterations to the stock geometry. What little stroke there is becomes confined to one extreme of each control arm and link's arc of motion. Also, when the springs are stiffer than the chassis, the chassis does all the flexing.
Fixing geometry problems in most modern cars with independent rear suspension is a matter of modifying the bushings or pick-up points to make the stock camber and toe curves work. Corollas are anything but modern and independent. Ironically, we had to steal tricks from muscle car and truck gurus to make our live axle stick and turn.
With a live rear axle, lowering the car does two critical things. First, the pinion angle is changed, so that, in static state, it's already pointing down. It does so even more when the car squats under acceleration (assuming it has enough power for the job). This means more resistance at the differential input shaft when the driveshaft yoke is contorted. More importantly, most cars are like the Corolla and have unequal lateral links. The anti-squat reaction from these links is further increased, since the lower link is now nearly parallel to the ground, while the short upper arms point up at a steep angle, pushing the instant center far below the center of gravity.
There really isn't a good fix for this without whipping out the welder and acetylene torch, but we're trying to solve it with an assortment of adjustable links, bars and brackets from Whiteline Automotive. It seems the AE86's popularity has stretched to Australia and Whiteline has invested a good deal of time developing and racing the platform, as well as writing papers on proper set-ups for it. Based on this experience, the company has developed a range of products that allow a Corolla to be adjusted for a variety of purposes.
To correct the pinion angle and reduce anti-squat reaction, we replaced the stock unequal-length lateral links with adjustable units. These are steel pieces with polyurethane bushings inserted in each end, which keep out some noise and vibration (unlike a heim joint). The lengths of the arms are adjusted with a threaded center section and jam nuts. There are many ways to screw this up when fiddling with the lengths, so we kept it simple. We put the lower links at the stock length to preserve the original wheelbase and adjusted the upper arms to force the pinion angle parallel to the ground. Depending on how far a car is lowered, there's a chance the upper arms will contact the axle housing under compression, so we had to move the axle through its range of motion to double-check. Otherwise, there would be suspension bind issues.
 The rear suspension bits from...  The rear suspension bits from Whiteline Automotive include adjustable rear upper and lower lateral links, an anti-roll bar and traction brackets at the ends of the axle. Note the upward angle of the upper arm and near-flat position of the lower bar, even with the suspension in full droop. By adjusting the lateral link lengths, pinion angle and anti-squat geometry can be tweaked. Traction brackets also add anti-squat by increasing the difference in angle between the upper and lower bars. |  Whiteline's solid front anti-roll...  Whiteline's solid front anti-roll bars come in two diameters, 24mm (adjustable as shown here) and a super-beefy 27mm bar that we're almost afraid to put on the car. |  With our lowered car hanging...  With our lowered car hanging in free air, the front anti-roll bar comes uncomfortably close to the chassis frame. Also note the exposed metal on the inner fender where the tire rubs, on account of the new steering hardware. |