Polyurethane
Common street-performance choice that reduces compliance compared with soft rubber, but can transmit more road input and requires correct lubrication/installation where specified.
SUSPENSION · NVH · JOINTS
Bushing / Joint Choice Changes NVH
Stiffer joints can sharpen response and reduce deflection while also transmitting more noise, vibration and harshness.
APPLICATION: Modified 1993–2002 Firebird / Formula / Trans Am suspension.
Spherical / articulating joints
Allow precise articulation with less compliance. UMI explicitly pairs polyurethane with Roto-Joints in street-performance combinations to retain some isolation while reducing bind.
NVH is not automatically a defect
After changing joint type, increased gear, road or impact noise may be a predictable consequence. But clunks, binding, loose hardware or metal contact still require diagnosis.
Choose by use
- Street/cruiser: prioritize articulation without excessive transmitted noise.
- Autocross/road course: prioritize repeatable geometry and freedom from bind.
- Drag: prioritize controlled axle movement and launch consistency while checking housing/bracket load.
FPV RULE
OBSERVE → MEASURE → ISOLATE → PROVE → REPAIR → VERIFY. Do not turn a symptom, DTC or catalog fitment label into a parts order.