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What are CDL retarders?


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CDL retarders are found on some commercial vehicles and are designed to help slow a vehicle and reduce the need to use your brakes. 

When used properly, the retarders reduce your brake wear and provide you with another option for slowing down. 

The main types of CDL retarders include:

  • Exhaust retarders.
  • Engine retarders.
  • Hydraulic retarders.
  • Electric retarders.

All retarders can be turned on or off, and some systems include options for adjusting the power of the reaterder. 

Retarders work by applying their pressure to the drive wheels whenever you release the gas pedal all the way. 

Note that the use of CDL retarders is restricted in some areas due to their loud noise. 

You should also note the applying retarders on bad tires or on slippery roads can cause your vehicle to skid. Retarders should be turned off when driving on wet, icy, or snow-covered roads. 

You can find more information about this topic in the Driving Safely (2) section of your official driver’s handbook. 

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