Trailer Surge Brakes: Federal Ruling | Centreville Trailer Parts LLC

This information is provided by Centreville Trailer Parts LLC as an “unofficial summary” of the ruling made by the FMCSA. The actual official document is some 35 pages long. It can be downloaded and read verbatim from the Federal Register Online.  The document number is: fr06mr07-10. This summary is our interpretation of the ruling.


In years past, there was a lot of confusion as to whether surge brakes were legal on trailers. The period of confusion started in 1997 and continued thru September 2004. Some states were ticketing surge brake equipped trailers because they did not comply with Federal Motor Carrier Administration (FMCSA) regulations governing commercial vehicles and/or those used in interstate travel. The confusion ended when the FMCSA asked the states to refrain from ticketing surge brake trailers and a study was undertaken to review the safety and track record of surge brake equipped trailers. The study was completed, and a final ruling was announced on March 6 of 2007.


  1. For Surge brake equipped trailers with a manufacturers rating of 12,000 lb GVWR or less, a maximum trailer to truck ratio of 1:75 to 1 is allowed. In example, a typical pickup truck with a manufacturers GVWR rating of 6000 lb can legally tow a trailer with a rating of 10,500 GVWR or smaller. (6,000 x 1.75= 10,500) If you want to know what size truck you will need to pull a known trailer, reverse the formula. In example, if you wanted to tow a trailer with an 11,500 GVWR, (11,500 divided by 1.75= 6572 GVWR truck or better is required.
  2. For trailers with a manufacturers rating of greater than 12,000 but equal to or less than 20,000GVWR, a maximum trailer to truck ratio of 1:25 to 1 is allowed. In example, a dump truck with a manufacturers GVWR rating of 15,000 lb can legally tow a trailer with a rating of 18,750 GVWR or smaller. (15,000 x 1.25=18,750)
  3. Surge brakes are not allowed on trailers over 20,000 GVWR.

The data plates or decals on a truck and trailer must be intact and readable for a police officer or DOT official to determine if the ratio of your truck and trailer are within these boundaries. If the data plates or decals are missing or illegible, the actual weight of the truck and trailer (loaded or not) will be used to calculate the ratio. Note that this method will greatly change the calculated ratio, such as an empty truck pulling an overloaded trailer. It makes sense to protect or replace missing or illegible data plates and decals. Typically, a data plate or decal on a trailer will be found near the front of the trailer, usually on the drivers side. A data plate for a truck is usually a decal, and is typically found on the driver doorpost, requiring the door to be open to see it.

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