4x4 Mag - Routine Trailer Servicing

Routine Trailer Servicing

Bradley Tow Coupling Servicing Guide

Welcome to the first in a series of Guides to Trailer Servicing. Over the next few Months, we intend to guide you through the basic routines that will help keep your Trailer in road worthy condition.

Why cover servicing of Trailers in a magazine for 4x4 owners you may ask? Just look around out there on the roads, and I'm sure you will notice that most 4x4s end up towing at one time or another, infact a large percentage of 4x4s are actually bought simply for their towing abilities. That is certainly the case for myself, my own 4x4 towing regularly every day of the week.

Working for a Trailer Manufacturer, all of the trailers I tow are kept in tip top mechanical condition, and generally as such never cause me a problem, the same, however, can't be said for a lot of the trailers I see being dragged behind 4x4s out there on the roads.

We've all seen them, converted caravans, home made chassis with old car axles slung underneath, infact in a lot of cases it seems that anything will do as long as it drags along behind the towing car. Some of the trailers I see make me cringe, probably accidents waiting to happen in my opinion. Do we need an MOT for trailers ?

For those of you reading this and feeling a twinge of guilt because most of the above sounds a bit like your trailer, well I'm sorry but this guide probably won't help you, but those of you with genuine professionally made trailers, using recognised branded parts, read on.

Bradley, Indespension, Avonride, all recognised brands of Towing Coupling and very popular in the world of trailers, caravans mainly use Knott or similar European brands. Looking around, the Bradley brand appears to be the most popular for Towing Couplings, so this in the October issue, I will cover the basics to look for to make sure that your trailer stays safe, and more importantly than that, it stays attached to your car!!

The following guide is to cover the Bradley 50mm Ball Coupling, it may, however, in general principle apply to most couplings.

1. Apply grease to BALL and to CUP OF BALL HEAD after cleaning each item. This is to be carried out EACH time that the trailer is towed.
2. Oil all moving parts weekly, to include the Handbrake mechanism, Coupling release mechanism and any brake linkage. Cleaning away any grit and dirt in the process.
3. Every 300 miles or 3 Months, apply grease to the grease nipples along the top of the drawtube using a grease gun. This will ensure that the Drawtube moves freely and applies the overun brake. Also check that the Drawtube is still free to rotate in the coupling housing, and that the tube does not have more than 2mm up and down or side to side movement within the housing, as this indicates excessive wear of the drawtube.
4. Every 3000 Miles adjust the wheel brakes at the brake back plate adjuster to take up any wear. DO NOT ADJUST FOR BRAKE WEAR ANYWHERE OTHER THAN AT THE WHEEL BRAKES THEMSELVES. DO NOT ADJUST THE BRAKE RODS OR LINKAGES TO ALLOW FOR NORMAL BRAKE WEAR.

Each time that the Trailer is coupled to your vehicle, carry out the following simple check to ensure that your Tow Ball or Coupling head are not excessivly worn.

ONCE COUPLED TOGETHER IF THE SQUARE LUG (1) AT THE REAR OF THE HEAD HANDLE (2) IS RESTING ON THE BOTTOM OF THE SLOT IN THE TRIGGER (3), EITHER THE COUPLING HEAD OR THE TOW BALL, OR BOTH, ARE WORN.

IF THIS IS THE CASE, CHECK FURTHER BY USING A NEW 50mm BALL. IF THE LUG REMAINS AT THE BOTTOM OF THE SLOT THE COUPLING HEAD IS EXCESSIVELY WORN AND SHOULD BE REPLACED. HOWEVER, IF THE LUG IS NOW RIDING NOTICABLY HIGHER UP THE SLOT YOUR ORIGINAL 50mm BALL SHOULD BE REPLACED.

N.B IF YOU NEED TO REPLACE YOUR COUPLING HEAD REMEBER TO CARRY OUT THE FIRST CHECK ONCE MORE AS YOUR 50mm BALL MAY NEED REPLACING AS WELL.

Following the above guide should ensure that your Trailer stays attached to the Ball on the back of your vehicle, wear in these two items can be very difficult to detect any other way, but it is critical that wear is detected before the Trailer detaches itself from the Tow Ball.

5. To check the condition of the Gas Damper within the coupling, fully apply the handbrake, and then attempt to push the drawtube into the housing, there should be a very strong resistance to this. Release the drawtube, and it should extend back out of the housing under the force of the Gas Damper. If the drawtube is easily pushed in, or does not extend automatically, the Gas Damper has lost it's pressure, meaning that excessive strain will be placed on the Trailers braking system, and that the Trailer brakes will possibly be prone to locking up unexpectedly.
We will be explaining how to change the Gas Damper in next Months edition, as well as servicing of brakes and wheel bearings.