The Problem: Hanger Slop
Most reverse-kingpin (RKP) trucks share a fundamental structural trait: the hanger floats inside the baseplate.
In a typical RKP design, the pivot cup, boardside bushing, and roadside bushing are all urethane components. Because every interface between hanger and baseplate is compliant, there is no rigid constraint anywhere in the assembly.
Under load, the hanger can deflect slightly relative to the kingpin and pivot. This deflection occurs in multiple directions:
- Lateral translation (X and Y)
- Minor axial play along the kingpin (Z)
- Angular micro-rotation around the kingpin axis
Collectively, this multi-directional compliance is what we call hanger slop.
This compliance is not inherently bad. In fact, it contributes to the smooth, lively feel many skaters associate with RKPs. It functions much like soft suspension in a car: absorbing irregularities and smoothing transitions.
However, that same compliance introduces delay and imprecision between rider input and wheel response. In freeride this can feel surfy and forgiving. In racing contexts, it can feel vague or inefficient.
The Solution (Across Four Axes)
A hanger insert addresses slop primarily by constraining lateral translation around the kingpin bore.
The concept was widely popularized by the first generation Rogue truck in 2018.
Unlike most RKPs, Rogues eliminated the traditional bushing seat. In most trucks, the conical or bowl-shaped seat constrains lateral bushing deformation and partially stabilizes the hanger in the X and Y axes.
The original Rogue removed this seat entirely.
With no seat and no rigid interface around the kingpin, lateral displacement increased. The solution was a 97A urethane insert dimensioned to fill the clearance between the kingpin and the hanger’s kingpin bore.
By eliminating this gap, the insert reduced lateral play and tightened the steering input to output relationship.
In simple terms:
Less clearance = less slop = more direct steering response.
A Clarifying Note on Axes
It’s good to note what the hanger insert does not solve.
Hanger inserts primarily reduce axial movement of the hanger due to lateral clearance around the kingpin.
They do not eliminate:
- Boardside bushing pre-compression due to rider weight (requires a z-axis constraining system)
- Pivot cup deformation (requires a spherical in the baseplate pivot hole)
The Slop-Constraint Spectrum
Today, there are functionally two different kinds of slop-constraining inserts:
- A Rogue-style urethane insert bushing.
- A Radikal-style spherical bearing.
Insert systems exist on a continuum from compliant to rigid:
- No insert
- Soft urethane insert
- Hard urethane insert
- Spherical bearing insert
Each step up the spectrum increases constraint and decreases compliance.
Rogue-style Urethane Insert Bushing
There are two general categories of urethane inserts.
Integrated / Proprietary Insert Systems
These are thick inserts designed into the hanger geometry itself. They occupy a large volume around the kingpin and materially affect how the truck articulates under load.
Because of the additional urethane mass, you can feel the increased compressive resistance. There is simply more urethane to squish.
These systems influence not just slop reduction, but often steering feel and rebound characteristics.
Aftermarket Slop-Stopper Inserts
These are thinner components, typically installed between the roadside bushing and the hanger. They are retrofit solutions.
They serve the same basic function, but because their volume is small, their effect is more localized. They reduce slop without dramatically altering total urethane mass in the system.
Durometer and Feel
Insert bushings typically range from approximately 95A to 100A.
- Softer inserts preserve some compliance.
- Harder inserts approach the feel of a spherical system.
As hardness increases:
- Precision increases
- Road vibration increases
- Ride harshness increases
Most skaters run matching insert hardness front and rear.
Some prefer a harder insert up front for sharper initiation. Rarely does anyone run a harder insert in the rear than the front, as that would be contrary to the dominant preference of having more active front steering compared to the rear.
Radikal-style Spherical Bearing
Some trucks are designed to accept a spherical bearing (often a generic COM6) inside the kingpin hole. For example. certain Rogue variants are compatible with both urethane inserts and spherical bearings.
A spherical bearing eliminates urethane compliance entirely at the kingpin interface. This is metal-on-metal constraint.
The result is near-maximal steering precision. Input translates directly into articulation with almost no intermediate deformation. Of course, for trucks without a spherical in the baseplate pivot, you still get some rotational slop as well as slop in the Z-axis from a height-unconstrained hanger.
However:
- Vibration transmission increases significantly.
- Surface irregularities are transmitted directly into the rider’s ankles.
- Forgiveness decreases.
- Form errors become more punishing.
It’s important to note that more precision is not universally better. It is context-dependent. In technical racing environments with high grip and clean pavement, spherical systems can offer measurable advantages. In freeride or rough terrain, this much precision can be excessive.
There are setups with a mix of the two as well; running a spherical in the front with an insert bushing in the rear in Gold Rogues is a common modification. This helps with faster heel-toe lean in the front, while keeping the rear damp for confidence and comfort.
Conclusion: Inserts Are About Constraint Tuning
Hanger inserts are not a magic performance upgrade. They are a constraint tool. All RKP trucks operate as compliant systems. The hanger is not a rigidly pinned object. It is supported by deformable interfaces that allow movement before articulation occurs. Inserts modify one of those interfaces: the clearance between kingpin and hanger bore.
By reducing that clearance, inserts:
- Reduce lateral translation
- Increase steering immediacy
- Increase vibration transmission
They do not:
- Change your truck’s base geometry
- Change rake
- Change bushing shape
- Eliminate pivot deformation
- Eliminate vertical compression from rider weight
An insert simply changes how tightly the hanger is located around the kingpin. From a systems perspective, you are trading compliance for constraint.
That trade is not universally good or bad. It is contextual. Freeride, rough pavement, and longer sessions often benefit from some compliance. Technical racing, clean pavement, and high grip often reward constraint.