How to Determine Correct Capacity and Size Electric Drum Brakes for Tandem Axle Trailer

Updated 06/27/2018 | Published 06/25/2018

Products Featured in This Question

Dexter Trailer Hub and Drum Assembly for 3,500-lb Axles - 10" Diameter - 5 on 4-1/2

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etrailer Electric Trailer Brakes - 7" - Left/Right Hand Assemblies - 2,000 lbs

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etrailer Electric Trailer Brakes - Self-Adjusting - 10" - Left/Right Hand Assemblies - 3.5K

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Wiring Kit for Hydrastar Electric Over Hydraulic Actuators

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Question:

I have 13inch rims. How do I know what size electric brake to use tire size is 175/80R13. I have dual axle and would like some recommendations on what to get.

asked by: Jaron

Expert Reply:

Electric drum brakes come in several sizes and each will be compatible with certain specific wheel sizes. You can best select replacement electric brakes for your tandem axle trailer by determining the axle weight rating. This ensures your brakes have the appropriate stopping power for the trailer's weight.

A trailer tire in size ST175/80R13 can have a weight rating of 1100 to 1600-lbs per tire so your axle rating is likely to be 2000-lbs to 3500-lbs. Usually an axle has a sticker or plate to tell you its weight rating; other times the trailer's main VIN sticker will list axle ratings along with other information such as its GVWR.

Axles rated for 2000-lbs and 2200-lbs typically use 7 x 1-1/4-inch brakes like # AKEBRK-2. These work with wheel diameters up to 13-inches. 3500-lb axles, which are fairly common, use brakes that measure 10 x 2-1/4-inches such as # AKEBRK-35-SA. This size of brake works with 13-inch wheel diameters and larger ones too.

You can confirm which size brakes you need by pulling one of your hubs and measuring its diameter and depth, as shown in the photo I included for you. We offer both manual-adjust brakes as well as self-adjusting ones like # AKEBRK-35-SA.

When you wire in your new brakes you can use either one of the two wires as ground since these magnet wires are non-polarized. Be sure to make solid ground connection to clean bare metal on the trailer frame, or to the ground terminal in your wiring junction box like # HS381-9000.

While you have your hubs pulled for installing the new brakes you might want to check your bearings for wear or damage. The part numbers for bearings are usually stamped right into their housings (see the second photo, please) and this makes it easy to find the replacements on our site. I linked two articles on bearings and one concerning lubricating grease in case you plan to replace these as well.