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Monroe Shock Absorbers view from under a vehicle.

Shocks 101

What Are the Differences Between Gas-Charged Twin Tube and Monotube Shock Absorbers?

Types of Shocks

Responsible for controlling excessive vehicle movements, shocks are a key component of your vehicle’s suspension system. When selecting replacement shock absorbers for your vehicle, you’ll have a choice between twin-tube and monotube shocks. While both types of shocks are designed to dampen the energy that is transferred to your vehicle when it hits a bump in the road, they differ in design and construction. Read on to learn the characteristics of both shocks so you can make the right choice for your vehicle.

Technician inspecting shocks.

What Are Twin-Tube Shocks & How Do They Work?

Designed to deliver excellent handling and control, twin-tube shocks are commonly used on passenger cars, light trucks and SUVs. As the name implies, twin-tube shocks have two cylinders – an inner tube that houses the piston rod, piston valve, hydraulic fluid and base valve and an outer tube that holds the reserve hydraulic fluid and the gas charge.

Featuring a piston rod that is connected to a piston valve, the piston rod moves up and down as the vehicle travels over bumps and dips; the fluid is forced through the piston valve and/or the base valve to control excess vehicle movement. When the shock is compressed, the piston pushes oil through the base valve into the reserve tube area. When the shock is extended, oil is forced through the piston valve and flows back into the inner tube.

Gas-Charged Twin-Tube Shock Advantages

  • Comfortable ride that is good for everyday driving
  • Reduces effects of aeration
  •  Provides consistent control
  • Reduces harshness
  • Reduces lean and sway while cornering
  • Less expensive than monotube shocks
  • Damage to external case doesn’t affect the shock



  • Minimal installation angles – won’t function if installed upside down
  • Susceptible to holding heat


What Are Monotube Shocks & How Do They Work?

Featuring a single tube that holds the oil, gas and piston valve, monotube shocks are a popular upgrade for off-roading and performance applications. The single cylinder is divided into sections: one section has fluid where the piston and shaft move and another section that holds the gas. A floating piston and seal separate the fluid section from the gas section.

Because there is no aeration or foaming, the valving of monotube shocks is more responsive. This combined with better heat dissipation are some of the reasons monotube shocks are ideal for racecars, off-road rigs and other performance applications.



  • Delivers more control and responsiveness
  • Runs cooler – improved heat dissipation
  • Higher gas pressure
  • Oil and gas are in separate chambers – no foaming
  • Firmer ride
  • Can be installed in different angles – even upside down
  • Less susceptible to shock fade



  • Impact to external tube can cause damage to the shock
  • Can be more expensive than twin-tube shocks


How to Choose the Right Shock for Your Vehicle

For passenger cars, Monroe recommends selecting the same type of shocks that the manufacturer originally put on the vehicle. If your car came originally equipped with twin-tube shocks, you should install twin-tube shocks on it and if monotube shocks came standard, stick with those.

For trucks and SUVs, you may have the choice of monotube or twin-tube shocks. How you use your vehicle will help guide your choice. For vehicles that rarely leave the pavement, you’ll appreciate the comfort of twin-tube shocks. If you spend time on the trail off-roading, the control and responsiveness of monotube shocks may be right for your vehicle.

Be sure to consult Monroe’s part finder to see the shocks that are available for your vehicle. If you have questions on selecting the right shocks for your car, truck or SUV, contact Gurus On-Call at 1-800-325- 8886.


Monroe Twin-Tube and Monotube Shocks

Whether you need a twin-tube shock for your daily driver or want a monotube shock for your off-road vehicle, Monroe has a shock for you.


Designed to restore a vehicle’s original factory drivability and performance, OESpectrum shocks provide an exceptional level of handling precision and control while filtering out noise, vibration and harshness. OESpectrum twin-tube and monotube shocks are available for passenger cars, SUVs and light trucks.

Monroe OESpectrum Shock


Ideal for vehicles with a higher center of gravity, Reflex twin tube light truck shocks feature Acceleration Sensitive Damping (ASD) valving technology that automatically adjusts the unit to absorb the impact, helping to reduce vehicle roll and dive. Reflex monotube shocks feature a high-pressure gas to provide additional spring rate to help maximize damping efficiency and control.

Monroe Reflex Shock


Designed for hardworking trucks, Magnum twin-tube shocks feature ASD for a comfortable ride while the monotube version delivers improved vehicle control over bumps, dips and potholes.

Monroe Magnum Shock

Magnum® Severe Service

Engineered for hardworking emergency, municipal, fleet and jobsite vehicles, Monroe Magnum Severe Service twin-tube and monotube shocks feature enhanced components for superior stability and ride control in the toughest environments.

Monroe Magnum Severe Service Shock


Ideal for hauling, Max-Air twin-tube shocks can be inflated or deflated up to 150 PSI to maintain level height with additional weight up to 1,200 lbs. (Capacity is limited by vehicle suspension, tires and transmission. See vehicle owner's manual.)

Monroe Max Air Shock

Load Adjusting

Ideal for light trucks that that tow or carry varying loads, Monroe twin-tube load adjusting shocks include a heavy gauge calibrated spring that adjusts to road and weight conditions to provide extra control when operating conditions get more demanding.

Monroe Load Adjusting Shock


Designed for midsize and full-size trucks and vans, Gas-Magnum twin-tube shock absorbers provide firm control without a harsh ride. With up to twice the fluid capacity of standard 1-in. bore shocks, they work more efficiently with less effort.

Monroe Gas Magnum Shock

Monro-Matic® PLUS

Engineered to get more miles from your car, Monro-Matic PLUS twin-tube shocks are equipped with nitrogen gas charge and feature Velocity Proportional Valving (VPV) technology for improved comfort at an economical price.

Monroe Monro Matic Plus Shock


Learn more about quality shocks, struts, and strut assemblies, find the right car part, or find a local repair shop today.

The content in this article is for informational purposes only. You should consult with a certified technician or mechanic if you have questions relating to any of the topics covered herein. Tenneco will not be liable for any loss or damage caused by your reliance on any content.