Recommendations For Converting To Electric Brakes On A M105A2 Trailer

Updated 12/27/2021 | Published 12/26/2021

Products Featured in This Question

Hydrastar Electric Over Hydraulic Actuator for Drum Brakes - 1,000 psi

(73)

$1041.78

10 Gauge Wire - Blue Primary - Per Foot

(104)

$1.84

Hopkins Engager Trailer Breakaway Kit w/ Charger, LED Tester, and 5 Ah Battery - Side Load

(747)

$59.83

etrailer Electric Trailer Brakes - Self-Adjusting - 12" - Left/Right Hand - 5.2K to 7K

(3026)

$186.02

Question:

I too have a M105A2 trailer. I just purchased it and I brakes are still the existing hydraulic system. I have also just purchased new wheels and tires it’s a lug pattern of 6 x 8 3/4. I will eventually be retro fitting the brakes at electric since I am also replacing the trailer plug to a 7 prong. I drive a 2017 F250 that has has the OEM assistance switch. With all that said, can you give me parts list for new brakes? I would also like to keep the manual brake chock locking if possible, it’s has worked like a champ even as old as this trailer is. I should be getting the new tire set up soon and would like to do the brakes while I have the tires off. Thanks.

asked by: Scott V

Expert Reply:

It looks like the M105A2 military trailers used an axle in the range of of our 5,200 to 7,000 pounds capacity brakes, so I recommend going with the etrailer.com Electric Trailer Brake Kit # AKEBRK-7-SA. These are self adjusting, so you will not need to mess with them every year to keep the braking consistent and will measure 12" in diameter and 2" wide. With all that said, I do also recommend double checking a few things.

First, make sure the 12" x 2" matches your current brakes/drums. The 6 on 8-3/4 bolt pattern is not one used with civilian market trailers, so the hub/drum may also be different.

Second, make sure the bolt pattern for mounting the brakes matches what this will come with. I included a picture with how it measures as explaining it would be confusing. Pictures are definitely worth a thousand words in this case.

Third, make sure your drum has a smooth surface for the brake magnet to adhere to. Not all hydraulic brakes can be used with electric brakes. If the surface is smooth, you are good to go. If it is not, let me know. I included a picture of what I mean for this as well.

You will of course need some wiring, like the # 10-1-1 (sold by the foot), to get everything working properly, but the Epicord Junction Box # 277-000141 makes this a lot easier and comes with a 7 Way plug pre-attached. It is also required for a trailer of this weight to have a break away kit installed, and the Hopkins Engager # 20099 will work perfectly for that.

I do have to mention that I am unsure what the manual brake chock is, so I cannot say if this function will be able to be retained or not.