Dexter Electric Trailer Brake Assembly - Self-Adjusting - 12-1/4" - Left Hand - 10,000 lbs

Dexter Electric Trailer Brake Assembly - Self-Adjusting - 12-1/4" - Left Hand - 10,000 lbs

Item # 23-438

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Dexter Axle Accessories and Parts - 23-438
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Product Images


  • Trailer Brakes
  • Electric Drum Brakes
  • Brake Assembly
  • Dexter Axle
  • 12-1/4 x 4 Inch Drum
  • LH
  • Self Adjust
  • 10000 lbs
12-1/4" x 4" Driver's-side electric trailer brake assembly fits 10,000-lb axles. Mounting flange has 7-bolt pattern. Self-adjusting brakes require little maintenance. Fits 15" or larger wheels. Call 800-298-8924 to order Dexter Axle accessories and parts part number 23-438 or order online at Free expert support on all Dexter Axle products. Guaranteed Lowest Price and Fastest Shipping for Dexter Electric Trailer Brake Assembly - Self-Adjusting - 12-1/4" - Left Hand - 10,000 lbs. Accessories and Parts reviews from real customers.

  • All Info
  • Reviews (1)
  • Q & A (12)
  • Videos (1)
  • Photos
  • Why etrailer?

Dexter Axle Accessories and Parts - 23-438

12-1/4" x 4" Driver's-side electric trailer brake assembly fits 10,000-lb axles. Mounting flange has 7-bolt pattern. Self-adjusting brakes require little maintenance. Fits 15" or larger wheels.


  • Electric brakes are easier to install and offer more user control than hydraulic brakes
    • Requires only an electric brake controller (sold separately) - no actuator or hydraulic lines necessary
  • Self-adjusting brakes automatically adjust to deliver optimum performance and braking power
    • No need for manual brake adjustments
    • Proper adjustment leads to better brake efficiency and less wear on your tow vehicle's brakes
  • Mounting bolts and hardware sold separately
  • Made in the USA


  • Application: most standard hub-and-drum assemblies, including Dexter and Lippert (LCI)
  • Configuration: left hand (driver's side)
  • Dimensions: 12-1/4" diameter x 4" wide
  • Mounting flange bolt pattern: 7 bolt
  • Wheel size: 15" or larger
  • Axle rating: up to 10,000 lbs
  • Limited 5-year warranty

K23-438-00 Dexter Electric Brake Assembly, LH 12-1/4" x 4" - Self Adjust - 10,000 lbs

Replaces 23-438

Video of Dexter Electric Trailer Brake Assembly - Self-Adjusting - 12-1/4" - Left Hand - 10,000 lbs

Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.

Video Transcript for Dexter Axle Trailer Brakes 23-438 Review

Today we're going to take a look at the Dexter 12 1/4 inch by 4 inch driver's side self-adjust electric brake assembly. It has a 10,000 pound weight capacity. Now electric brakes are easier to install. They offer more control than hydraulic brakes. Electric brakes require only an electric brake controller which we do sell separately. There's no actuator or hydraulic lines necessary.

Now the size is given as a 12 1/4 inch by 4 inch. This is a driver's side electric trailer brake assembly. The driver side means it's the left hand side of the vehicle. Now on a new assembly you'll usually have a sticker that will you tell you right hand or left hand, but if that sticker wasn't on there, the easiest way to tell is look at the size of the pad. You see the pad goes from here to here. If we flip it around this pad goes all the way from here all the way to here.

This pad is longer, and this pad is shorter. The shorter pad is the primary shoot. That will always face the front of the trailer. That will tell you it goes this way. That means it will be a left hand driver side assembly.

The size they give is 12 1/4 by 4 inch. Where that is measured the 12 1/4 would be from the edge of this pad all the way over to the edge. The overall diameter is right at 12 1/4 inches. Then the 4 inches would be the width of the pad itself, see right at 4 inches. Now the friction material that's used on this pad is fully bonded, it's not riveted to the shoe. It gives you a lot longer life, more breaking torque.

Now this assembly happens to be a self-adjusting brake. You can tell that by the cable that goes around the pulley that attached to a lever right down here. Now a self-adjusting brake does not require a periodic manual adjustment like standard brakes. Basically, after you install this you'll make your additional adjustment. Then they'll self-adjust as you go. Now this is designed to fit a 7 bolt brake mounting phalange. Let me show you the back here. You can see here 1, 2, 3, 4, 5, 6, 7. Now the mounting hardware is not included. We do sell that separately on our website. Now this brake assembly is certified by USSAE standards. Again to go over the specs we mentioned it's a 12 1/4 by 4 inch wide. The axle rating that it sits on is up to 10,000 pounds. Again, this is a left hand driver side. It does require the use of 12 1/4 inch brake drums. Now these are electric brakes, so electric brakes do need power. If you see in the back here there's 2 yellow wires. Those 2 wires will be connected. One goes to a brake feed, one goes to the ground. You can do either wire for either function. They're both yellow wires, so it doesn't matter which one to which. That should do it for the review on the Dexter 12 1/4 by 4 inch driver side self-adjust electric brake assembly with a 10,000 pound weight capacity.

Customer Reviews

Dexter Electric Trailer Brake Assembly - Self-Adjusting - 12-1/4" - Left Hand - 10,000 lbs - 23-438

Average Customer Rating:  5.0 out of 5 stars   (1 Customer Reviews)

12-1/4" x 4" Driver's-side electric trailer brake assembly fits 10,000-lb axles. Mounting flange has 7-bolt pattern. Self-adjusting brakes require little maintenance. Fits 15" or larger wheels.

- 23-438

Website was very easy, (with no attitude from the no nothing parts man) received order in 2 days and for less money than locally. 172606


Ask the Experts about this Dexter Axle Accessories and Parts

Do you have a question about this Accessories and Part?

  • Replacement 12-1/4 x 4 Inch Brakes for 10,000 Pound Dexter Trailer Axles
  • If your drums are 4 inches wide where the brake shoe pad makes contact with the inside of the drum then you will need 12-1/4 by 4 inch brakes # 23-438 for the left and # 23-439 for the right. If you are measuring the overall depth of the drum then you likely need the 12-1/4 by 3-3/8 assemblies such as # AKEBRK-10L which would fit on Dexter axles.
    view full answer...

  • How to Determine if a Hub Was Originally Designed as an Oil Bath or Grease Hub
  • An easy way to tell if your hubs were originally oil filled or packed with grease is to remove the cap of the hub. Typically, if it is a press-in cap it is a grease hub, and if it is a screw-in cap it is an oil bath hub. Not only do semi trailers use oil bath hubs, there are many heavy duty trailers that will use them as well. If you have been putting grease in your hub so far and it has been working well for you, then I would just stay with the grease. I attached an FAQ article on...
    view full answer...

  • Parts Needed to Replace Grease Lube Hubs with Oil Bath Hubs
  • You will not need to replace the brakes on your trailer when converting from grease lube hubs to oil bath hubs. The oil bath hubs that you choose should come with the proper bearings, seal and oil cap for that hub. You will want to check the part numbers on your bearings and seals to ensure you select the correct hubs for your spindles. We carry two oil bath hub and drum assemblies. Trailer Hub and Drum Assembly, # 8-219-9UC3-A, fits 5,200 lb to 7,000 lb axles with spindles that require...
    view full answer...

  • Width of Brake Pads on 28 Foot Gooseneck Trailer With Dexter 10K Axles
  • To determine which brake assembly you need, measure the width of your brake linings, as shown in the photo I edited for you. If your existing brake shoes measure 4 inches wide, the # 23-438 you mentioned would be an example of a good replacement for you if your existing brake assemblies use 7 mounting bolts (some use 4) and the diameter of the assembly is 12-1/4 inches in diameter when measured from the outside of one brake shoe directly across to the outside of the other shoe as shown...
    view full answer...

  • Adjusting Dexter 10K Electric Trailer Brakes
  • The Dexter 10K electric brakes # 23-439 (right side) and # 23-438 (left side) will have to be manually adjusted using the adjustment wheel below the magnet. To adjust the brakes you will use a small screwdriver or similar tool to turn the adjustment wheel. The wheel pushes out the shoes. You will keep turning the wheel until the pads lightly, but consistently, drag on the drum. The brakes should be adjusted like this anytime you notice braking starting to weaken. I have included a link...
    view full answer...

  • Two Year Old Big Horn 3670RL 5th Wheel Trailer Leaking Grease into All Four Brake Assemblies.
  • If all four wheels on your 2-year-old Big Horn 5th wheel trailer have suddenly leaked wheel bearing grease into the brake assemblies my initial thought is that perhaps the bearings have recently been re-packed (which is typically to be done at 6 or 12 month intervals depending on manufacturer) with either too much grease or with grease of an incorrect grade. While there are general-purpose grease products that can be used in multiple applications, wheel bearings usually require a grease...
    view full answer...

  • Replacement Electric Drum Trailer Brakes for a 10,000 Pound Wells Cargo Trailer
  • The brakes on your Wells Cargo trailer could just be in need of adjustment. On drum brakes you will adjust the brakes so that there is a slight but constant drag of the pads on the drum when you turn the wheel. To see how to manually adjust trailer brake assemblies check out the video I attached, fast-forward to the 4:35 mark of the video. If the trailer has 2 axles then you likely have de-rated 6K axles (5200 pound axles). This size would be 12x2 inches. they mount to a 5-hole mounting...
    view full answer...

  • Servicing Electric Trailer Brakes on a Tandem Axle Trailer with 10,000 Pound Axles
  • I have included 3 videos that will help you. One specifically is on installing electric brakes. The trailer in that video did not start with brakes so it will be a little different. However it will still show you how to remove the hub and adjusting the brakes. I have all included a video just on installing a hub. And finally I have included a video on bearings that should be very helpful. Some tips that I will add is to make sure that you clean off all of the old grease and use new grease...
    view full answer...

  • Will Dexter 12-1/4 x 4-Inch Left-Hand Electric Brake # 23-438 Fir 10K Dexter Axle D1012
  • The brake assembly you referenced, Dexter 12-1/4 x 4-Inch Left-Hand Electric Brake # 23-438, is indeed rated for 10K axles. This brake matches up to Right-Hand brake # 23-439. You can check for fit on your existing axle's brake flanges by checking the mounting bolt pattern. Both of these brakes use a 7-bolt mounting pattern. As long as your drums are 12-1/4 x 4-inches and your brake flanges use the 7-bolt mounting pattern these will work great as replacements.
    view full answer...

  • How To Adjust And Test Electric Brakes On A Trailer
  • It sounds like you need to adjust the brake on your trailer. If you have electric brakes like the Dexter Electric Brake Assembly LH, part # 23-438, you can make the adjustments pretty easily. I have attached a video that shows trailer brakes being installed. If you go to about the 4:40 mark on the video it shows how to adjust the brakes. I have also attached a photo of an electric brake that shows where the adjustment wheel is located. You can also test the magnet on the brake that...
    view full answer...

  • Trailer Brake Magnets for Dexter 10k Axles
  • Not all trailer brake magnets are the same, but since we know you have a Dexter 10,000 lb trailer axle the correct magnets would be the part # BP01-301 which would be correct for the brake assemblies # 23-438 and # 23-439.
    view full answer...

  • How to Tell if Trailer Drum Brake Assemblies are On the Right Side
  • If you pull of the hubs on your trailer you should see the actuating arm holding the magnet below the spindle. If you imagine the arm as the end of an arrow it should be pointing towards the front of the trailer. If yours are on the wrong sides they would perform like you described.
    view full answer...

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Info for this part was:

Photos by:
Theodore B
Expert Research:
Michael L
Expert Research:
Michael H
Installed by:
Jeff D
Expert Research:
Jameson C
Expert Research:
John H
Updated by:
Adele M
Expert Research:
Adam R
Updated by:
Sarah W
Updated by:
Alexander C
Photos by:
Stacy F

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