February 16, 2023 1 min read
Suspension bushings are one of those things that many don’t pay attention to until they have a problem. But while bushings don’t earn many points at a meet, these little rubber, polyurethane, or metal things can actually have a huge effect on the performance and driveability of your car.
Bushings connect every part of your suspension to the rest of your car. What happens at those pivot points depends on the material and design of your bushings.
Most vehicles come with soft rubber bushings that are designed primarily to absorb noise, vibration, and harshness (NVH). Under heavy cornering or braking loads, they’ll squish and deflect.
Since bushings link suspension parts, that causes mid-corner changes in suspension geometry, meaning your bushings can contribute to changing camber and toe as the car rolls.
This is sometimes intentionally designed into bushings, but it is not always ideal.
Excessive bushing deflection from soft or worn out bushings can cause unpredictable handling behavior in addition to sluggish response and sloppy body control.
For Subarus, hardened rubber bushings are available through the STI Group N motorsports program that reduce deflection with only a minimal change to NVH. They are sometimes more difficult to install than other alternatives, but are a good compromise between ride and performance.
Polyurethane bushings have some advantages, but aren’t necessarily the perfect solution they’re often advertised as being. They’re usually quite a bit stiffer than rubber bushings and easier to install, but they restrict off-axis articulation. Because some bushings pivot on more than one axis, binding can occur if that articulation is restricted.