If you’ve ever felt your car swaying or wandering while driving on the highway, you’re not alone. Many drivers experience this unnerving sensation, and it can happen for a variety of reasons.
What causes highway sway?
There are a few potential causes of highway sway:
- Wind: Strong crosswinds can push your car from side to side, especially if you’re driving a light or tall vehicle like an SUV or truck.
- Speed: Driving too fast can make your car unstable, increasing swaying at higher speeds.
- Tire issues: Worn tires, under or over-inflated tires, uneven tread wear, or mismatched tires side-to-side can all contribute to sway.
- Suspension problems: Worn shocks or struts, loose steering components, unbalanced wheel alignment, and other suspension issues reduce your car’s stability.
- Vehicle load: Carrying too much weight, uneven weight distribution, or a heavy load on the roof can cause the car to sway.
How to prevent highway sway
While some sway on the highway is normal, excessive and constant swaying is dangerous. Here are some tips to minimize sway and keep your car stable at highway speeds:
- Check tire pressures: Keep tires inflated to the pressure recommended by the manufacturer. Check pressures monthly.
- Inspect tires: Look for uneven tread wear, which indicates an alignment or suspension problem. Replace worn tires.
- Get wheel alignment: Have a professional align the wheels at least once per year or any time you replace tires.
- Check shocks and struts: These should be inspected every 50,000 miles. Replace if worn.
- Load properly: Distribute weight evenly and avoid overloading. Heavy cargo should go over the rear axle.
- Drive appropriately: Obey speed limits, slow down for conditions, and avoid sudden acceleration/braking.
- Install stabilizer: Consider adding an anti-sway bar or stabilizer for top-heavy vehicles.
When to have swaying checked out
Minor swaying is not uncommon, but having your vehicle regularly checked and serviced can minimize the problem. See a mechanic promptly if you experience:
- Excessive swaying, wandering, or loss of control
- Uneven tire wear
- Car pulling to one side
- Unusual tire noise or vibration
- Bottoming out or bouncing
- Leakage around struts or shocks
A mechanic can inspect the suspension, steering components, wheel alignment, and tires. This will identify any worn parts that need replacement.
How sway bars reduce sway
Many vehicles come equipped with rear sway bars or anti-roll bars. This is a stabilizer bar that connects opposite wheels and reduces body lean when cornering. How do sway bars work to reduce highway sway?
- Connects left and right suspension: The torsion bar joins the left and right suspension and wheels.
- Resists suspension differential: It works against one wheel dropping or rising independently of the other.
- Reduces body roll: As the vehicle leans into a turn, the bar twists and pushes back to reduce lean.
- Improves handling: The bar keeps the vehicle more level, improving tire grip and control.
The stiffness of the sway bar affects how much it reduces body roll. Stiffer bars decrease roll but can compromise ride comfort and traction. So most automakers tune the bar stiffness for an optimal balance.
Upgrading or adding sway bars
Many performance and sport vehicles come with beefed up sway bars for increased handling response. Upgrading to stiffer sway bars or adding them to vehicles that don’t have them can improve stability and reduce sway. Things to know about sway bar upgrades:
- Front and rear bars work together and should be tuned accordingly.
- Larger diameter bars are stiffer than smaller ones.
- Solid bars are stiffer than hollow ones of equal diameter.
- Stiffness affects steering feel and traction as well as roll.
- Polyurethane bushings last longer than rubber but transmit more noise and vibration.
- Adjustable or removable bars allow tuning adjustability.
Consult a performance shop about selecting optimal sway bars if considering an upgrade.
Other suspension modifications for stability
Along with sway bars, other suspension modifications can also improve highway stability and reduce sway in performance applications. These include:
- Lowering springs – Lower center of gravity for flatter cornering.
- Stiffer shocks/struts – Better control of weight shifts and vertical wheel motion.
- Chassis braces – Connect suspension mounting points to increase chassis rigidity.
- Suspension bushings – Stiffer bushings reduce compliance for crisper response.
- Wider track width – Broader stance increases stability.
Such modifications trade some ride quality for increased performance and response. Only make suspension changes if you are an experienced performance driver.
How much swaying is normal?
A slight amount of highway swaying and wandering is inevitable, even with properly maintained vehicles. But how much is normal? Experts recommend having any sway evaluated if:
- Steering requires constant small corrections to stay straight.
- You feel votre car drifting near lane markings.
- The vehicle leans excessively during cornering.
- You hear odd tire noises indicating uneven wear.
As a rule of thumb, your hands should not need to move more than 3 inches from center to correct swaying at highway speed. Anything more indicates an alignment, tire, or suspension issue.
Conclusion
Experiencing your vehicle swaying on the highway can be unsettling, but is often correctable. Causes range from winds to worn components. Maintain proper tire pressure, get regular wheel alignments, have shocks and steering inspected, and avoid overloading the vehicle. For performance applications, sway bars and other suspension upgrades can maximize stability. But have any excessive or worsening sway checked out immediately by your mechanic.