Do you remember the Mickey Thompson stadium off road racing series that travelled across the nation bringing short course off road racing to thousands of fans? The late 80’s and early 90’s brought us new technology in suspension design that shocked the world. Take a look at the former Ivan Stewart driven Toyota off road race truck built by Cal Wells and the crew at PPI.
The truck is lovingly being restored by Allen Russell, aka RaceHacker. The truck was built before bypass shocks were invented. It was also built in a time period when rising rate suspension was first being used on dirt bikes. Toyota (PPI) use “A LOT” of rising rate suspension design on this truck. Front suspension uses triple rate torsion bars on the lower arms & a single “bump stop” torsion bar on the top arm. All stages are adjustable and many different diameter (rate) torsion bars are available. The Bilstein shocks are mounted in a lay down, cross over fashion. The front suspension is capable of 18+” of wheel travel, but is limited to 16″.
If you thought the lay down, crossover shock mounting on the front was interesting, check out the rear suspension! Cantilever arms on rollers, bump control on shock extension, dual torsion bars..strange, but it worked! The rear suspension is also “limited” to around 16″, but can get much more. Toyota had limited the suspension on the truck to get it to fly through the air level. Rear suspension uses a cantilever front arm that extends (pulls) the shocks on wheel up travel & compresses the shocks on wheel drop (normal rebound). Complete opposite of how most suspensions function. The cantilever arm also uses a torsion bar for the spring. The rear arms also use torsion bars for an additional spring. As the axle cycles forward, the spring rate is increased at a rising rate as the axle pulls on the arm/linkage forward. The cantilever arms rest on top of the axle between a set of rollers. As the wheels compress, the roller roll up the arm changing the rate (rising) of the shocks and torsion spring). Confused yet? Perhaps the photos below will help you out!
We hope to keep everyone updated on the restoration of this famous Toyota off road race truck. Follow along for future updates! Via Race Dezert