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  1. #1
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    Brake wiring guage - stock - or upgrade

    This is going to sound like a strange question to some.

    I discovered the OEM brake wiring on my trailer may be undersized. I say may as I have not confirmed it yet.
    My new axles arrived and they came wired with 14 AWG. I need to connect everything up, but the cross tube wiring is 14 awg as well as what comes out of the backing plates.

    To help with my new install I pulled up the Dexter service manual https://www.dexteraxle.com/user_area...ice_manual.pdf Page 11 says I should be using 12 awg, or possibly 10 awg as the run from the bed plug to the rear brake is right at 30' if you include the 7 pin cord length. From what I can tell the 7 pin cord has a 12 awg brake wire in it based on web information. I will be verifying this.

    Now page 21 of the above service manual indicates the magnets can draw 3A each or 12A all together for my double axle trailer. Using the Blue Sea chart found here https://www.bluesea.com/support/arti...r_a_DC_Circuit and using the total run length both ways as you should for a DC circuit it says I need 10AWG using the 3% critical that I think applies in this situation. its 12 awg if I go the 10%. Its border line with the 14 awg at 10% drop allowed.

    The brake wiring in the OEM harness running to the brakes appears to be 14 awg.

    First question - Would you consider the brake wiring a critical or noncritical circuit? If non critical, is the 14 awg OK. Is the 10% voltage drop allowable as this reduces the total amp available at the magnets. My gut says it is a critical circuit, but I don't know how the magnets react to reduced voltage and how often I would pull full amperage at the magnets. Most videos show 2.8 to 3A when brakes applied and amperage to the magnets are checked.

    Second - the belly is wide open currently so I have access to all the wiring. Should I upgrade to 12 awg or even the 10 awg?

    Background - my stock 10" brakes have been OK, not stellar, but OK. The new axles have 12" so a big improvement there. I am currently running about a 6 gain, medium initial.

    Also if anyone has information on brake magnet performance over varying voltages, could you please post it

    Thought on all this....BTW I am a retired civil engineer with enough electrical training to be dangerous.

    Thanks
    2018 Reflection 150 Series 220RK 5th wheel. B&W 25K OEM Companion, Steadyfast system, 2022 F350 SRW 6.7 King Ranch 8' bed, Trailer reverse lights, rear spare tire holder, storage tube, sumo springs, Victron MultiPlus and Solar

  2. #2
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    Quote Originally Posted by powerscol View Post
    This is going to sound like a strange question to some.

    I discovered the OEM brake wiring on my trailer may be undersized. I say may as I have not confirmed it yet.
    My new axles arrived and they came wired with 14 AWG. I need to connect everything up, but the cross tube wiring is 14 awg as well as what comes out of the backing plates.

    To help with my new install I pulled up the Dexter service manual https://www.dexteraxle.com/user_area...ice_manual.pdf Page 11 says I should be using 12 awg, or possibly 10 awg as the run from the bed plug to the rear brake is right at 30' if you include the 7 pin cord length. From what I can tell the 7 pin cord has a 12 awg brake wire in it based on web information. I will be verifying this.

    Now page 21 of the above service manual indicates the magnets can draw 3A each or 12A all together for my double axle trailer. Using the Blue Sea chart found here https://www.bluesea.com/support/arti...r_a_DC_Circuit and using the total run length both ways as you should for a DC circuit it says I need 10AWG using the 3% critical that I think applies in this situation. its 12 awg if I go the 10%. Its border line with the 14 awg at 10% drop allowed.

    The brake wiring in the OEM harness running to the brakes appears to be 14 awg.

    First question - Would you consider the brake wiring a critical or noncritical circuit? If non critical, is the 14 awg OK. Is the 10% voltage drop allowable as this reduces the total amp available at the magnets. My gut says it is a critical circuit, but I don't know how the magnets react to reduced voltage and how often I would pull full amperage at the magnets. Most videos show 2.8 to 3A when brakes applied and amperage to the magnets are checked.

    Second - the belly is wide open currently so I have access to all the wiring. Should I upgrade to 12 awg or even the 10 awg?

    Background - my stock 10" brakes have been OK, not stellar, but OK. The new axles have 12" so a big improvement there. I am currently running about a 6 gain, medium initial.

    Also if anyone has information on brake magnet performance over varying voltages, could you please post it

    Thought on all this....BTW I am a retired civil engineer with enough electrical training to be dangerous.

    Thanks
    I would do 12 AWG. It's highly unlikely that you would pull the maximum amount of current for an extended period of time, unless you yank the emergency stop cable and walk away from it, (or if the pin gets pulled while you are driving and don't notice it).

    You are correct on the calculations, but the maximums are generally referred to for "extended durations".

    Personally, I would go 12 AWG and call it good.
    Mark & Mary. Full-timing across the USA (and Canada)!
    Current Coach: 2021 Grand Design Reflection 320MKS
    Current Rig: 2019 Ford F350 SD Crew Cab, w/8' box, Lariat, SRW, 6.7l Diesel

  3. #3
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    Quote Originally Posted by MoonShadow_1911 View Post
    I would do 12 AWG. It's highly unlikely that you would pull the maximum amount of current for an extended period of time, unless you yank the emergency stop cable and walk away from it, (or if the pin gets pulled while you are driving and don't notice it).

    You are correct on the calculations, but the maximums are generally referred to for "extended durations".

    Personally, I would go 12 AWG and call it good.
    Thanks
    I ran across this video that was very helpful.
    https://www.youtube.com/watch?v=8dt11D0am6Q
    To convert the wire size he mentions
    https://www.electricalcarservices.co...le/c-p-0-0-520
    2018 Reflection 150 Series 220RK 5th wheel. B&W 25K OEM Companion, Steadyfast system, 2022 F350 SRW 6.7 King Ranch 8' bed, Trailer reverse lights, rear spare tire holder, storage tube, sumo springs, Victron MultiPlus and Solar

  4. #4
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    I had some brake wiring issues on my 399 and I ended up running all new wire from the 7 way pigtail back to the brakes. I used 12awg wire compared to the stock 14awg and I'm not sure if it was just in my head, but I felt like I had better brake performance afterwards.
    2023 Momentum 398M-R
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  5. #5
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    Quote Originally Posted by FT4NOW View Post
    I had some brake wiring issues on my 399 and I ended up running all new wire from the 7 way pigtail back to the brakes. I used 12awg wire compared to the stock 14awg and I'm not sure if it was just in my head, but I felt like I had better brake performance afterwards.
    You probably did!
    Mark & Mary. Full-timing across the USA (and Canada)!
    Current Coach: 2021 Grand Design Reflection 320MKS
    Current Rig: 2019 Ford F350 SD Crew Cab, w/8' box, Lariat, SRW, 6.7l Diesel

  6. #6
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    On the other hand, why not convert to disc brakes?
    Mark & Mary. Full-timing across the USA (and Canada)!
    Current Coach: 2021 Grand Design Reflection 320MKS
    Current Rig: 2019 Ford F350 SD Crew Cab, w/8' box, Lariat, SRW, 6.7l Diesel

  7. #7
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    Quote Originally Posted by MoonShadow_1911 View Post
    On the other hand, why not convert to disc brakes?
    Cost? Running new wiring is much cheaper, maybe easier, than installing disc brakes. And I have read that it improves the braking by a decent margin. It's what I would do, but I'm notorious cheapskate.
    Howard and Peggy
    2019 Momentum 351M, and 2018 RAM Cummins dually 6-speed.
    His: 1999 Honda Interceptor
    Hers: 2013 Spyder ST-S

  8. #8
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    Quote Originally Posted by Hoopy Frood View Post
    Cost? Running new wiring is much cheaper, maybe easier, than installing disc brakes. And I have read that it improves the braking by a decent margin. It's what I would do, but I'm notorious cheapskate.
    Bah! Like we say in the auction business, "It's only money!"
    Mark & Mary. Full-timing across the USA (and Canada)!
    Current Coach: 2021 Grand Design Reflection 320MKS
    Current Rig: 2019 Ford F350 SD Crew Cab, w/8' box, Lariat, SRW, 6.7l Diesel

  9. #9
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    Yeah, but with auction houses, it's always other people's money.
    Howard and Peggy
    2019 Momentum 351M, and 2018 RAM Cummins dually 6-speed.
    His: 1999 Honda Interceptor
    Hers: 2013 Spyder ST-S

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