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Sway Bars

Friction or hydraulic devices that connect the trailer to the tow vehicle and reduce trailer sway at highway speeds.

Also called: sway bars, sway control bars, anti-sway bars

Sway bars are friction or hydraulic devices that connect the trailer to the tow vehicle and reduce trailer sway at highway speeds. Common on travel trailers; not needed on fifth wheels.

How they work

Sway bars create resistance that dampens lateral motion:

  1. Trailer starts to sway (from wind, passing trucks, or uneven loading)
  2. Sway bar resists the lateral movement
  3. Damping force brings the trailer back to centered
  4. Stability restored

Types of sway bars

Friction sway bars

  • Adjustable clamps that grip the hitch and trailer
  • $50-$200 for basic friction bars
  • Manual adjustment for sensitivity
  • Common on smaller trailers

Hydraulic sway bars (more advanced)

  • Hydraulic cylinders that automatically respond
  • $200-$500
  • More effective on heavier trailers
  • Better in severe sway events

Integrated with weight distribution hitch

  • Built into WDH systems (Equal-i-zer, Reese)
  • Most effective overall
  • Required for trailers above 5,000-7,000 lb
  • See weight distribution hitch

When you need sway bars

Required or strongly recommended on:

  • Travel trailers over 4,000 lb GVW
  • Trips on windy or mountainous routes
  • Tow vehicles smaller than ideal for trailer
  • Higher-speed highways (65+ mph)

When sway bars aren’t needed

  • Fifth wheels (kingpin hitch eliminates sway)
  • Very small trailers under 3,000 lb on appropriate tow vehicle
  • Slow, short trips on calm days

Common rental scenarios

For travel trailer rentals:

  • Most owner-provided WDH systems include integrated sway control
  • Some owners require sway bars on top of WDH for heavier trailers
  • Older trailers may have separate friction bars
  • Verify at pickup: what sway control is included

Installation considerations

Sway bars typically:

  • Connect to hitch ball assembly
  • Mount to trailer A-frame
  • Require specific spacing
  • Adjustable for sensitivity

For renters, owner should install before pickup. Verify they’re connected and functioning during walkthrough.

When sway becomes dangerous

If you experience sway:

  1. Don’t accelerate — slowing makes it worse
  2. Don’t brake hard — can amplify sway
  3. Don’t oversteer to compensate
  4. Maintain steady speed
  5. Apply trailer brakes alone (if trailer brake controller present)
  6. Pull over safely when sway subsides

Sway that escalates can cause jackknife or rollover.

Causes of sway

  • Improper loading: too much weight at trailer rear
  • Insufficient tongue weight: less than 10% of trailer weight
  • Worn or improperly adjusted WDH
  • Tow vehicle too small for trailer
  • High crosswinds
  • Passing semi trucks creating air pressure
  • Tire pressure problems
  • Worn shocks on tow vehicle

What’s normal vs. concerning

Normal:

  • Slight swaying when passing trucks pass
  • Gentle correction when wind gusts
  • Minor side-to-side motion

Concerning:

  • Increasing sway amplitude
  • Sway that doesn’t dampen out
  • Truck pulling toward sway
  • Lateral motion at highway speeds

Safety equipment that helps

Beyond sway bars:

  • Trailer brake controller in tow vehicle
  • Weight distribution hitch properly adjusted
  • Quality shocks on tow vehicle
  • Properly rated tires at correct pressure
  • Appropriate tow vehicle size

In rental walkthroughs

Ask the owner during pickup:

  • What sway control is installed?
  • How is it adjusted?
  • What symptoms should I watch for?
  • What’s the cancellation policy if I’m uncomfortable?

Trailer rental safety depends on proper sway control. Don’t skip this conversation.