Triple lock towing head fitting instructions

Here is a guide to replacing a standard coupling head with a ‘triple lock’ style coupling on a 50mm box section drawbar.

Below is a triple lock head kit. This comes with all the nuts and bolts needed to fit it, but there are a few other things you will also need.

Triple lock head kit

You will need this drawbar adaptor plate, plug holder and carabiner. The drawbar adaptor is used because the hole centres of the triple lock head do not quite match up with those in the drawbar from the original head. This adaptor saves you from having to re-drill holes in the drawbar.

Drawbar adaptor kit

First of all, remove the two bolts on top of the old coupling that hold it onto the drawbar. You will notice that the small triangle shaped stand and length of chain (secondary coupling device) will also come away from beneath the drawbar when these bolts are removed.

Standard coupling head

Using the two bolts from the original head connect the drawbar adaptor to the drawbar. Re-fit the triangle shaped stand and secondary coupling device using these bolts as well.

You will notice in the example below that a plug holder has been fitted using one of these same bolts. A plug holder is a legal requirement in the UK and so you must remember to fit one.

You must also remember to only attach one end of the chain when re-fitting it. This secondary coupling device is also a legal requirement in the UK, so you must remember to re-fit this too.

Drawbar adaptor plate, plug holder and chain

Place the triple lock head on the drawbar adaptor. Two bolts connect the new head to the drawbar much like the original, except one of these bolts is about to be secured in such a way it can only be removed with a grinder.

In the example below you can see that the rear bolt is protected by a security device. A thin walled socket is required to tighten this bolt as a regular one is too thick to fit inside the ‘cup’ shaped device.

Triple lock head secure bolt

After tightening the protected bolt, a small disk of metal is hammered into the top of the security device to seal it. This metal disk has tapered edges to make it easier to hammer in.

Securing the coupling head

The only way to remove this now is to cut through it using a grinder to reveal the bolt inside.

Triple lock head sealed bolt

Finally, you must attach the carabiner to the loose end of the chain. Normally both ends of this chain would be attached to the drawbar, leaving a loop that could be hooked over the tow ball. This head requires a drawbar adaptor though, so the length of chain is no longer long enough. The carabiner allows you to thread the chain around the tow ball and then clip it back onto itself where convenient.

Triple lock head fitted

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