Differences in Sway Bar End Types

Question

Accepted Answer

The design of the ends of a sway bar (also called an anti-roll bar) is a critical engineering choice that directly affects how the bar connects to the vehicle's suspension and, consequently, how it performs. The main differences lie in how they are connected to the end links and their adjustability.

Here’s a breakdown of the common types and their implications:

1. Based on Connection Type

A. Drilled Hole (Fixed Eyelet)

Description: The end of the bar is flattened and has a single hole drilled through it. A bolt from the end link passes through this hole.

Implications:

Simplicity & Cost: This is the most common and inexpensive design, often found on OEM (original equipment manufacturer) street vehicles.

Fixed Rate: It provides a single, fixed level of stiffness (sway rate). The leverage ratio is predetermined by the design.

Durability Concern: The constant pivoting motion can cause the hole to wear out over time, leading to clunking noises. The bolt is also in shear stress.

B. Tapered/Threaded End

Description: The end of the bar is machined into a tapered shape with external threads. A Heim joint (spherical rod end) or a similar connector on the end link screws directly onto it.

Implications:

Performance-Oriented: This design is prevalent in high-performance, racing, and aftermarket applications.

Reduced Binding: The spherical joint allows for multi-axis articulation without binding, which is crucial for suspensions with extreme travel or precise alignment needs.

Preload Adjustment: It allows for easy fine-tuning of preload (ensuring the bar is neutral when the car is level).

C. Integrated Link (Flag Mount)

Description: The end of the bar has a built-in, flat "flag" or clevis with two holes. It connects to the end link using two bolts, creating a bushing-mounted connection.

Implications:

OE Design for Certain Vehicles: Common on some modern trucks, SUVs, and German automobiles (e.g., many BMWs and Porsches).

Improved Articulation: The two-bolt design allows the bar to pivot more freely through its arc, reducing stress on the bushings.

Replacement Complexity: The end links for this design are often more complex and expensive to replace.

2. Based on Adjustability

This is the most significant functional difference for enthusiasts.

A. Non-Adjustable Sway Bars

Description: Typically have simple drilled holes at each end.

Implication: Offers only one level of stiffness. The driver cannot change the car's roll resistance without replacing the entire bar.

B. Adjustable Sway Bars (Multiple Hole Settings)

Description: The ends have multiple drilled holes at different distances from the bar's center axis.

Implication:

Tunable Stiffness: By moving the end link to a different hole, you change the lever arm length.

Softer Setting: Connecting the end link to a hole closer to the bar's center reduces the leverage, making the bar act softer and reduce roll resistance.

Firmer Setting: Connecting the end link to a hole farther from the bar's center increases the leverage, making the bar act stiffer and increase roll resistance.

This allows drivers to fine-tune the car's balance (e.g., induce more oversteer or understeer).