Thread: Air Trailer Brakes

Originally Posted by garrycol

My new truck has the old trailer brake system that has an air/vacuum tank under the rear of the car and a contoller under the dash that is linked into the trucks braking system. The trailer requires a power assist master cylinder that has a air/vacuum hose that plugs into the back of the truck.

Is there any point in keeping this or should I get rid of it and replace it with a more modern electric brake controller. I haven't seen a trailer with a power assist master cylinder for years.

Thanks

Garry

Garry

There are still a few older caravans and heavier trailers, particularly car trailers out there that can use the vacuum/mechanical or vacuum/hydraulic systems and in fact they are a very good and robust system. They don't require extra alternator power as do multi-axle electric brakes and when the trailer is over 2 tonne the breakaway system is easier*. Generally trailers of over 2 tonne GTM have to have either vacuum or air or electric operated brakes and over-ride operation brakes are not "legally sufficient" when the GTM is over 2 ton. Given that most 109/110 Land Rovers weigh over 1.5 tonne and the tare weight of a car trailer is frequently over 500 Kg then it is probably illegal to tow any long wheelbase Land Rover on most commercially available car trailers.

In short, my opinion is if the vacuum brake system is on the vehicle, it is not doing you any harm why remove it? The reality is that I am intending to fit up dual line vacuum brakes to both of my S2Bs. I have the kits, and have a friend who has a caravan with vacuum/hydraulic brakes.

Fit an electric brake controller as well if you wish. Or if you are sneaky - you can get additional wiring harnesses for the Prodigy electric controller and then swap the controller between vehicles. (Unlike some cheaper controllers, the Prodigy does not need to be leveled into the car.)

Diana

* A 2+ tonne brake-away brake system is required to hold the brakes on for 15 minutes after disconnection from the towing vehicle. On the vacuum system this is supplied by a reservoir tank on the trailer and the 2nd (supply) pipe on the vehicle. In an electric break away system, this requires an additional functioning battery on the trailer with it's own charging circuit from the vehicle. Excluding the NATO plug, how many 8 pin trailer plugs do you know?

they're a bloody good system...

not quite as good as proper air brakes but IMHO better than some of (but not all) of the electrical systems. for most of the reasons already outlined but with the final addition that if you use the right hitch on the front you can have all in one a vac on demand braking system with an over run brake, a breakaway control AND a parkbrake in the same place. I think they can still be had new if you ask in the right places.

Thanks Diana/Dave

I thought they were a good system - I will never own a trailer with one and any trailers I am likely to have to tow will have an electric system. Therefore I will fit an electric brake controller but just curious if I should also keep it as well.

The tank etc is at the rear of the truck where I might want to put a second LPG tank later or a petrol long range tank. On a 101 you need a long range tank to drive short ranges.

Garry

If your not going to use it and have something else to go in the place its filling turf it its just going to be somethine else that will collect dust dirt grime water and then lead to rust.

Originally Posted by garrycol

Thanks Diana/Dave
... The tank etc is at the rear of the truck where I might want to put a second LPG tank later or a petrol long range tank. On a 101 you need a long range tank to drive short ranges.
Garry

Garry Can understand that you may want to have an LPG tank and don't know the size of the tank that you have in place.

There are a couple of options:

1. If you have a large reservoir tank and may not ever use it. I have a tank designed to fit in cars, it is about 18" long and about 6" in diameter. This could possibly be fitted elsewhere along the chassis rail or wheel arch and I'll swap it with you if you like.
2. Remove the system and the Diana Refuse Service will collect it from you and may even pay you scrap value!

Diana

Originally Posted by Lotz-A-Landies

this requires an additional functioning battery on the trailer with it's own charging circuit from the vehicle. Excluding the NATO plug, how many 8 pin trailer plugs do you know?

this is what the AUX pin is for, usually hooked up to the reversing lights, but how many people do you know of who have reversing lights on a trailer?

when i was working at a place building gooseneck trailers, every trailer and every vehicle that had a gooseneck hitch fitted got wired to use the aux pin on the plug to chage the tailer battery

On my defender 130 I regularly tow more than 2.5 tonne.
I use a vacuum break away system.
I was fitted by me even though it is old hat simply because the trailer I use had the system already on it.
THe truth is the electric battery breakaway systems are easier to live with.
The parts to repair the vacuum systems are getting harder to get.
Most brake or trailer places dont want to know about them these days.
Go to PBR direct for parts and the best way to go is factory exchange second hand parts.
MY trailer with the breakaway vacuum brakes can be used as a over ride system behind a normal vehicle as well.
The vacuum system can be mechanical or hydraulic on the trailer.
With a diesel getting enough vacuum to run the system can be a problem.
Yes my trailer has the parking hand brake.
I think only vacuum can offer all this.
Electric is easier to fit and is the current standard in break away systems.

My understanding is the break away electric systems will work through the standard 7 pin plug.