What Is a Telma Retarder?

Mary McMahon
Mary McMahon

A Telma retarder is a type of auxiliary brake that can be fitted to a vehicle to handle much of its braking needs. Such brakes can be installed on light to heavy vehicles that experience frequent stop-and-go traffic like garbage trucks, buses, and fire equipment. They do not replace the service brakes on the vehicle, but reduce wear and tear on the original braking system to keep the vehicle running smoothly for a longer period of time. A technician can install Telma retarders on a vehicle and test them to make sure they are operational.

Temla retarders are often installed in vehicles that make frequent stops like garbage trucks.
Temla retarders are often installed in vehicles that make frequent stops like garbage trucks.

These brakes operate frictionlessly, a departure from traditional drum or rotor brakes. When a vehicle is in motion, two rotors move harmlessly past each other, allowing the wheels to freely rotate. When the operator applies the brake, it generates an electromagnetic field that pulls the rotors against one another to slow the vehicle. The Telma retarder can be used in a variety of conditions, and may replace service brakes for a substantial component of the time.

Telma is a specific brand name; other companies make other versions of retarder brakes for a variety of vehicles. Auxiliary brakes like a Telma retarder help prevent dangerous situations caused by brake failure. Heavy equipment is hard to stop with conventional brakes, and the brakes may see considerable wear and tear while the vehicle is in service. There is a risk that the operator might feel for the brake while going down an incline or in an emergency and get an inadequate response because the brakes are so worn.

The eddy current system used with these brakes can take some getting used to for drivers. Operators may need special instruction in how and when to apply the braking system to get the best effects and reduce the risk of injuries. As with other braking systems, regular maintenance is critical. The brakes are most safe and effective when they are properly maintained and regularly checked for any signs of problems that might pose a threat to drivers or passengers.

A service technician can evaluate a vehicle to determine if a Telma retarder would be a good fit. If it is not, other retarder brakes may be available and could be used for similar effect. Telma retarder distributors have their own personnel who can provide assistance with installation, service, and education for drivers who want to learn how to use the system safely.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


@Markerrag -- I can remember growing up and hearing about vehicles full of families getting crushed by big vehicles with brakes that failed on those mountain highways.

The Telma retarder and other clever braking systems may not sound exciting, but the things have saved a lot of lives. Thank goodness for them.


These are also great for heavy vehicles that go long distances down deep grades. There was a time, not long ago, when the service brakes that came on big vehicles were the things that kept them from stopping. Those proved to be only so-so for slowing big vehicles down on steep grades because one could burn through them fairly quickly under heavy use.

You can still see a lot of those mountain highways with special ramps on hills for runaway vehicles. The scary thing is those used to be necessary. They aren't needed so much anymore and that is a good thing.

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