Good Sam Club Open Roads Forum: Tech Issues: Brake Wire
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Sjm9911

New Jersey

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Joined: 07/01/2020

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Posted: 07/21/21 09:12pm Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer wrote:

Sjm9911 wrote:

I get the principles and practices, i just figured the manafature has allready considered the drop into the specs. So its designed to work woth the guage it has and to upgrade it will not nessassarly equate better stopping.


The trailer manufacturer only goes by published minimum specs. Those specs are based on total current draw over the distance from the axle manufacturers.

Dexter Axle used to have a chart calling out the MINIMUM wire ga for certain distances for a certain quantity of brake magnets. Not sure if they still have that on their website.

Because the magnets are rated 3A draw at 12V,each axle can draw as much as 6A.

So a single Axle trailer typically is rather short you could get away with a minimum of 16 Ga which would handle the max current of two magnets.

Longer trailers with two axles means you have the potential for 12A at 12V and typically the minimum recommended wire is 14 Ga because of the current.

RV manufacturers let the wire selection go to the frame manufacturer that they buy from (RV manufacturers typically "farm out" the frame building to a third party). That frame manufacturer will typically use the minimum recommended wire ga from the axle manufacturer.

Using the minimum basically is to cover only the max amperage draw, not the best performance.

The brakes will work, just not as well as they would if you were to have less resistance in the wire run.

This gets very apparent with folks who have larger and heavier trailers like 8K-12K 30ft+ trailers. Many of those folks end up scrapping the drum brakes in favor of disc brakes using Electric over Hydraulic system.. Your talking a $1K overhaul of the brakes..

In low voltage world wire resistance is a major problem, with 12V a .1V loss can make the difference of a device working or not working.

The magnets strength is directly affected by how much current flows through it. The current is controlled by the resistance of the magnet and the voltage across the magnet.

If the resistance of the wire going to the magnet is increased, the voltage at the magnet is reduced which reduces the strength of the magnet.

The less strength the magnet has it will not grab the drum surface hard enough to mechanically push the brake shoes against the drum.

That all equals far less effective brakes.

So, in reality, reducing distance of wire and/or increasing the wire size can have a huge impact on improving your drum brakes braking power.

Since you can't shorten the wire length, increasing the wire size is the only way to go.

I have made this mod to two trailers, 20ft and 26ft both dual axle and both rated 7K GVWR, in both cases the wire upgrade resulted in better braking, enough that I was able to reduce the brake controller output considerably.


This explains it well. And probably why i had a smaller wire hooked up. Actually i was thinking about what i did, and forgot to consider other facters. Like other campers may have larger runs and more wheels and larger magnets. All in all that would lead to a generic more is better approach. So my first statment may be only good for me and my size unit. Thats for the detailed explanation.


2012 kz spree 220 ks
2020 Silverado 2500
Equalizer ( because i have it)
Formerly a pup owner.

Vintage465

Prunedale CA.

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Posted: 07/22/21 07:10am Link  |  Quote  |  Print  |  Notify Moderator

12/2 jacketed brake wire is the proper conductor. I would not go less.

https://www.ebay.com/itm/352212792104?hash=item520184b328:g:USEAAOxyAs9SRbIh


V-465
2013 GMC 2500HD Duramax Denali. 2015 CreekSide 20fq w/450 watts solar and 465 amp/hour of batteries. Retired and living the dream!

Gdetrailer

PA

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Posted: 07/22/21 11:13am Link  |  Quote  |  Print  |  Notify Moderator

Vintage465 wrote:

12/2 jacketed brake wire is the proper conductor. I would not go less.

https://www.ebay.com/itm/352212792104?hash=item520184b328:g:USEAAOxyAs9SRbIh


$5.99 per 10ft plus $4.99 shipping, $11 for 10ft??

$1 per ft..

That is an insane price!

You can buy that same jacketed wire in the same 12 Ga at Amazon for $.79 per ft..

But 12ga is not an upgrade and if one is going to go through the hassle of changing the wire, one might as well go big and upgrade further.

Additionally, you do not need to use that plastic jacketed wire, an improvement and better wire is Neoprene jacketed "SJ" rated wire which uses a heavy neoprene rubber outside jacket and the inside wires also are jacketed in neoprene rubber. That advantage of SJ type cord is the wire strands are very fine and allows the cord to flex very easy.

Standard jacketed RV brake wire on the other hand uses large strands which are far less flexible and much more brittle and prone to breakage.

The more flexible SJ cord will hold up better in areas that the wire must flex a lot, like where they touch the axles!

Can get 2 wire 10ga SJ cord for around $1.15 per ft maybe a bit lower if you search around a bit.

Not everything must have "RV" on it to use, heck even 12Ga speaker wire or zip (lamp) cord can be used in a pinch..

Not every must be sourced from Ebay either, much better places that sell much better quality and prices.

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