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How to Measure to Determine the Size Trailer Brakes Needed For Hydraulic Drum Replacement


Where does the measurement come from to determine if I have 2-1/4 or 2-1/2inch brakes? I need to replace the brakes on a Road King boat trailer with 3700# axles. It seems the wheel cylinder is blown out and rather than buying piece parts you kits seem to be the best option.


Helpful Expert Reply:

To determine the size of the brake assemblies you need you have to measure the depth and width of the hub drum on the axle like what you see in the picture I attached. The most common size is 2-1/4 inch wide like the # T4071600-500 that you referenced.

click to enlarge
helpful expert reply by:
Jameson C

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Follow up Questions

Matt O.

12 x 2.5 drum trisaler brakes i just want the whole brake whitout botor i need probably 5

Etrailer Expert
Reply from Jon G.

Sounds like you're looking for the Brake Kit # 23-428-429 which is rated for a 7,200 lb axle. This kit comes with both the right and left brake assemblies and it doesn't come with the hub and drum - just the brakes.

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