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

Question

Question:

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.

asked by: Chris

1

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.

expert reply by: Jameson C

1

click to enlarge

Matt O.

8/7/2020

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

Jon G.

8/18/2020

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.

Joe C.

9/4/2025

10" x 2.5" - double axle can you give me a part number

Jameson C.

9/4/2025

@JoeC Are you sure the width is 2.5 inch and not 2.25 inch?

Joe

9/4/2025

2.25 sorry

Jameson C.

9/4/2025

@Joe Gotcha, you'd just need the # AKEBRK-35-SA.

See All (7) Replies to Joe C. ∨

Answer 1

Hi Ben; the difference in the drum size won't make a difference as long as you have a #84 spindle with #L68149 inner and #L44649 outer bearings. The #AKHD-545-35-EZ-K is 10" x 2-1/2" while the #84546UC3-EZ is 10" x 2-1/4" and…

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Answer 2

Hi Christopher! While we do not have full kits for brakes and drums, we can definitely put one together! Do you happen to know the bearing numbers for the axle? Easiest way to know would be to find the axle tag/sticker and see what Sloan says, but we…

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Answer 3

Great question, Matt, and you’ll be glad to know: no programming or special setup needed for the Electric Brake Assembly 12" ABS #LC83PX. These brake assemblies work just like standard electric brakes on your trailer’s wiring. One wire goes to…

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Answer 4

It sounds like you are speaking of the wires for the brake magnets. If this is correct, you will need to connect one of the wires to the brake controller output wire on your trailer connector and the other wire will need to be grounded to a clean…

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Answer 5

Hey Tom. The highest capacity drum brake assemblies we have for a 4 bolt brake flange are the Dexter Electric Trailer Brakes item #23-105-106-09. These are a 6,000 lbs set that are mainly used with AL-KO/Hayes axles. Do you have any part numbers or…

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Answer 6

Even though I cannot comment specifically on the grease you used because I am not familiar with it, I can tell you the best grease for trailer bearings is a a grease with a rating of GC-LB, which just means it is made to withstand very high…

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Answer 7

The inside diameter and the depth of the brake drum is what determines the necessary width of the brake pads. For example, the 10 inch x 2-1/4 inch Electric Brake Shoe, part number BP04-090 that you refer to would fit a brake drum with a 10 inch…

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Answer 8

We don't have any way of knowing the brakes you need for your Shorelander boat trailer but can tell you how to determine the right ones. To determine the brake assemblies that will fit your trailer, you need to know your axle's weight…

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Answer 9

Hey Paul, for your 2022 Grand Design Momentum 351MS you can use the Dexter Electric Trailer Brakes #23-180-181 for replacement brakes. These brakes will work with Dexter 7k axles, measures 12" x 2", and has a 5 bolt mounting flange.

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Answer 10

For a 12,000 lb Dexter axle the correct replacement brake magnets would be the part #BP01-306 which can work on either side of the trailer. Or for all new assemblies you'd want the part #23-442-443 which is one for each side. These come with…

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Answer 11

I went out to our warehouse and measured the dimension of the Dexter Replacement Magnet for Dexter 12-1/4" Electric Brake Assemblies, #BP01-306. The magnet measured 4 inches long x 2-1/2 inches wide. This magnet is designed to replace the magnet…

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Answer 12

You would know to replace brake shoes the same way you would know with a vehicle. If performance is suffering and adjusting the brakes does not help and there are no other issues causing the poor performance it is probably time to change the brake…

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

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