These aren’t your typical leaf springs
Mustang leaf springs tend to get a bum rap, but that’s only because the typical designs out there are circa 1975. We’ve seen people buy a set, be disappointed in the results, then blame it on their 50 year old car. But that’s simply not true. When we bring modern technology and design to leaf springs, we can create a rear suspension that performs, installs simply, and keeps down the weight.
The most common complaint associated with leaf springs is wheel hop, the chatter you feel when accelerating. Poor leaf spring design allow the front half of the leaf to deform/deflect causing axle wrap up which snaps back and induces wheel hop.
That’s why our springs have been designed with an extra two leaves toward the front, with a beefy wrap to add additional strength. We have guys with 900+ hp applications running these springs and they’re still not experiencing wheel hop.
The other big complaint we hear is ride quality. More often than not, people end up selecting a solid or urethane bushing for the spring saddle which we’ve found to be problematic for two reasons. First, it makes the ride extremely harsh, and second, it actually binds up the rear and prevents the suspension from working well during cornering.
For a stock setup, leafs have two jobs: they move up and down to absorb shocks, but they also move side to side, working to keep the axle centered. During cornering, the leaf is moving both up and down, and side to side, absorbing bumps through the turn without knocking the car off course. Replacing the bushing with a solid material prevents the spring from moving side to side, increasing bind and ultimately resulting in unpredictable feel. That’s why we actually prefer the stock rubber for the leaf shackles as it allows the suspension to do it’s job.
We do recommend and include a urethane bushing for the leaf eyelets, as this helps to keep the car under control during acceleration and braking far better than the standard rubber.
We’ve also intentionally recurved the spring to bring the ride height to what we consider to be the best, about 8″ from the pinch weld to the ground. This slightly lowered setup puts the suspension in the best place for overall geometry.
We’d also recommend upgrading to our panhard setup to help further control the side-to-side movement of the rear end.
This setup is a simple, budget-friendly option that is highly effective both on the street and track. We’ve seen dramatic improvements in feel, responsiveness, and ride quality by simply replacing stock or other aftermarket components with this setup.
A note about using our leaf springs
A stock Mustang motor angle is generally about 3.5 degrees transmission down from the motor. The front of the third member usually aims down about 1 degree. When you apply the throttle the pinion usually climbs about 4 degrees, equally miss-aligning the front and rear universal joints during load (3.5 down in the front, ~3.5 up at the front of the third member.)
Because our leafs are more robust in the front half, they limit the climb by about 2 degrees. As a result, we recommend putting a two degree shim (or lowering block) in between the leafs and the housing with the fat side of the wedge in the front. Without this shim or adjustment, you may experience some vibration as a result of driveline misalignment.