Thread: trailer breaks/kits

Ahh that's more like the the TB-Class (3500Kg) trailers with the electric or electric over hydraulic actuators, must have a means of holding the trailer on a defined slope with no power to the electric brake system. That means a cable parking brake setup on a separate calipers for disc brakes or the dual actuated shoes on drum brakes. Drums are actually the better system in outright performance, but with the issue of corrosion, water ingress and fade. Plus drums can be a pain to set up, calipers are easier to swap pads out bleed and do all the other maintenance tasks.

The other interesting thing with TB-Class trailers is the breakaway rule, requiring a breakaway switch and a battery setup that operates the brake system long enough to stop the trailer. Now that's great in theory, but the rules are a bit ambiguous on the use of safety chains with a 2501-3500Kg trailer meaning that some inspectors are requiring crossed safety chains (which should be for the 2001-2500Kg weight class) which effectively makes the breakaway system useless and leaves potentially 3500Kg's flopping around on the back of the (usually lighter) tow vehicle. I'm not sure why they are doing this, as the rules are meant to be interpreted in the safest manner and for me the breakaway system is much better than the crossed chains in that weight class.

I had a fairly robust discussion with the local VTNZ outfit with that trailer I had to convert - now this was for a trailerable barge and the rig had a road weight of 3485Kg (fairly well worked out haha). They went into the computer on one WOF check and it was registered as a TA-Class single axle general purpose trailer. Oops. So the point of correcting the rego details opened a few worm cans, one of which was the override coupling rated at 2500Kg failed the new WOF check, only one safety chain, one master cylinder so brake performance was below spec for two braked axles and it went on from there including the fact that the parking brake wasn't up to spec for the weight as the master cylinder went straight to the floor. About $3500 later in hydraulic actuator and the TB-Class kit to convert the thing to the 'right' spec and I went back in - only to get failed on no safety chains which was a requirement of the trailer inspection form at the time. Hmmm - as I said not required due to the breakaway switch and demonstrated it in use. Scratch head, followed by the other two inspectors summoned, heads together for the obligatory pow-wow, heads up for a meercat looking at the trailer, heads back down, hmmm again. Inspector says wait one, steps into the office and a call to somewhere and 5 mins later walks out and everything was right in the world. Well I got the sticker haha.

Our first thought with this issue of the insufficient braking performance was to fab up a dual-master-cylinder adapter to fit two master cylinders to the override coupling, But it wouldn't meet the specs for the weight class so no point... Would be good for a 2500Kg trailer that you want to have good stopping power though and it woud give good redundancy to have two separate hydraulic systems on the one trailer.

Originally Posted by No.3

The other interesting thing with TB-Class trailers is the breakaway rule, requiring a breakaway switch and a battery setup that operates the brake system long enough to stop the trailer. Now that's great in theory, but the rules are a bit ambiguous on the use of safety chains with a 2501-3500Kg trailer meaning that some inspectors are requiring crossed safety chains (which should be for the 2001-2500Kg weight class) which effectively makes the breakaway system useless and leaves potentially 3500Kg's flopping around on the back of the (usually lighter) tow vehicle. I'm not sure why they are doing this, as the rules are meant to be interpreted in the safest manner and for me the breakaway system is much better than the crossed chains in that weight class.

The reason for this is, recommending safety chains being used in conjunction with breakaway (NZTA Verm in 2021) was to add safety to oncoming traffic if the trailer was to disengage with the tow vehicle and cross into the path of another vehicle. Electric drum brakes are prone to imbalance and with breakaway activated can veer off the path of travel, if indeed the breakaway works at all.

Originally Posted by Mathias

The reason for this is, recommending safety chains being used in conjunction with breakaway (NZTA Verm in 2021) was to add safety to oncoming traffic if the trailer was to disengage with the tow vehicle and cross into the path of another vehicle. Electric drum brakes are prone to imbalance and with breakaway activated can veer off the path of travel, if indeed the breakaway works at all.

So what's the point of a breakaway system if you tie the trailer to the towing vehicle which means the breakaway can't (or more than likely won't due to the relative length of the breakaway cable vs the safety chains) activate?

Also, what usually happens if the tow hitch disconnects from the towball is that the trailer heads off the camber to the left dragging the tow vehicle's arse left and punching the front across the centerline. Bloody counterproductive is what that is, safest option is a) build the roads properly with correct cambering, and b) have the greatest mass vehicle separate from the tow vehicle and apply it's brakes as it heads off to the left following the (correctly road engineered) camber.

Not getting at you personally @Mathias, but the brains trust in Wellington needs to sort this sh1te out and decide which way they are going with these things because the status quo is just confusing and way behind best practice overseas. The fact we can't run air/over systems like other jurisdictions is a complete joke.

Originally Posted by No.3

So what's the point of a breakaway system if you tie the trailer to the towing vehicle which means the breakaway can't (or more than likely won't due to the relative length of the breakaway cable vs the safety chains) activate?

Also, what usually happens if the tow hitch disconnects from the towball is that the trailer heads off the camber to the left dragging the tow vehicle's arse left and punching the front across the centerline. Bloody counterproductive is what that is, safest option is a) build the roads properly with correct cambering, and b) have the greatest mass vehicle separate from the tow vehicle and apply it's brakes as it heads off to the left following the (correctly road engineered) camber.

Not getting at you personally @Mathias, but the brains trust in Wellington needs to sort this sh1te out and decide which way they are going with these things because the status quo is just confusing and way behind best practice overseas. The fact we can't run air/over systems like other jurisdictions is a complete joke.

Very true, NZTA have left it way too long to address the ruling and now it'll be a huge expense to the tax payer to put it in a more workable format. There is talk & plans of alignment with NZ 5467:1993 Code of Practice for Light Trailers but this has to be brought into the current century to be effective for a start, which they (NZTA) have acknowledged.
To scare the folks out there more, there's currently no legal standard required to build a tow bar suitable for under 3501kg for a vehicle with a WoF.

Anyway, you & I aren't going to fix it on the forum. As suggested, the OP would be wise to have at least one axle braked, preferably hydraulic override disc of good quality manufacture, proper safety chains & suitable tow bar etc.