Trailer Brake Wire Size

[101RRS]

I am currently building a pulse buster for my RRS. I am using standard trailer wiring cable for the internal wiring but this got me thinking about the size of wire used for the trailer braking circuit.

From what little I know about electric trailer brakes I assume the solenoids in the actual brakes pull a decent load - I would have thought too much for the lightweight wire strand in standard wiring cabling that the trailer lights use.

I have checked the wiring in my trailer and it seems extremely lightweight - so what size wire is recommended for the brake circuit of campers ad trailers.

Cheers

Garry

[Hoges]

I fitted a 12 pin "flat" plug and receiver for the camper (from Jaycar IIRC) which has several pins of a larger diameter for heavy current draw (i.e. electric brakes). I think I used 10 gauge for the braking circuit, including the cable from the (P3) controller under the dash to the rear bumper mounted socket. Probably overspecc'd but it was handy and certainly does the job!

[Pedro_The_Swift]

around 5-6amps per brake;)

[101RRS]

around 5-6amps per brake;)

That what I would have thought - there is no way the standard offering in trailer electrical cable is going to carry that at a full 12v when required over the distance.

Garry

[Pedro_The_Swift]

I'm pretty sure the BSL is running on the edge cable wise:eek:,,

I'm not even sure the 12 pin plug is rated to 20A:eek:
must check that one day:D

[bee utey]

Trailer cable comes in different ratings, Narva 5874 cable is nominal 4mm 7 core cable rated at 15 amps, should be available from a decent sparkie shop or truck parts place. Or you could add a 4mm 2 core to your el cheapo 5 core using spiral wrap.

[101RRS]

Trailer cable comes in different ratings, Narva 5874 cable is nominal 4mm 7 core cable rated at 15 amps, should be available from a decent sparkie shop or truck parts place. Or you could add a 4mm 2 core to your el cheapo 5 core using spiral wrap.

For sure there are ways around it - but the basic cable supplied and plugs etc on most trailers are really not up to scratch - makes me wonder how many trailers are not getting full braking capacity in emergency stops where a full 12v+ should be getting to the brakes.

Garry

[bee utey]

For sure there are ways around it - but the basic cable supplied and plugs etc on most trailers are really not up to scratch - makes me wonder how many trailers are not getting full braking capacity in emergency stops where a full 12v+ should be betting to the brakes.

Garry
I suppose you could rig a volt meter to the brake controller to see what the full braking output voltage actually is, allowing for battery voltage being as high as 14V.

I agree many brake wiring cable sizes are undersized but the brakes come on anyway. Is there any roadworthy checking of trailer braking efficiency?

[Pedro_The_Swift]

We just went through a 1st van rego (not renewel ) and I was hoping there is some form of brake test,, but no.
not even a handbrake check,, i know cos the handbrake doesnt work on ours. All they do is measure the van.

edit; The actual rego inspection is done by private company, in our case Trailaway here in Toowoomba,
a gas valve was replaced,
did they drive test the brakes? who knows,, and how do you test ALL 4 are working?
apart from physically seeing all 4 wheels lock up?

[Graeme]

My van went through a NSW 1st time rego check last year (it was purchased interstate) and no brake test was done. I understand there is no trailer/van brake test for less than 2 tonnes as they don't require a break-away brake device and therefore cannot be tested independently.

[Hoges]

I'm pretty sure the BSL is running on the edge cable wise:eek:,,

I'm not even sure the 12 pin plug is rated to 20A:eek:
must check that one day:D






for info... I just checked my 12 pin Narva: 7 pins are rated at 15 Amp while the remaining 5 are rated at 35 Amp...
cheers

[slug_burner]

I'd be surprised if the standard wiring could not deliver the current required. It is a matter of how hot the wire will get. Sure there will be a voltage drop but I think the melting insulation is going to be your first problem. And I think the electromagnets are going to be your current limiters. The electromagnets in the brakes are going to have much thinner wire and a much longer length of wire as it is wound multiple times around the metal core.

[SimonM]

Or you could add a 4mm 2 core to your el cheapo 5 core using spiral wrap.

This is what i have just dóne, but I ran 6mm dual core which fits nicely in the large round 7 pin trailer plug.