Towing Mirrors and What They Are For

These are a legal requirement rather than a convenience, in most of the places people tow. Where the trailer or caravan is wider than the car measured across its mirrors, you must be able to see behind it — and a standard mirror cannot.

The failure people complain about is not the product. It is fitting. A mirror on a loose strap, or clamped to glass rather than to the housing, vibrates at speed until the image is unreadable, and gets returned as faulty.

A note on this guide: this rests on published construction-and-use requirements and manufacturers' fitting instructions, not on mirrors tested here. Requirements differ by country and change — check the rules for every country on your route. See how we test.

The problem, as it appears

A first tow with a borrowed or newly bought caravan, and the discovery in the first mile that the door mirrors show the side of the caravan and nothing else. There is no view down either side and no way to judge whether the lane beside you is clear.

Or the later version: mirrors fitted, and the image shakes so badly at motorway speed that they are worse than nothing.

Why the obvious approach disappoints

Adjusting the standard mirrors out does not work. Their range is limited and the caravan is wider than the range; pushing them out simply moves the blind area rather than removing it.

Fitting extension mirrors carelessly produces the vibration complaint. Three specific causes:

• Clamped to the glass rather than to the mirror housing, so the whole assembly hangs off a part designed only to hold a mirror still.
• Strap tension too low, so the mirror is held by friction that lets go at speed.
• Grit under the contact points, which stops the clamp seating flat and marks the paint at the same time.

None of those is a product fault, and all three are why the category has a reputation for being useless.

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What actually matters

1. The view you are aiming for

Not the caravan. You should see past it — the full length of the trailer plus the lane beside it, with the trailer's flank at the inner edge of the image.

If the mirror is filled with your own caravan, it is aimed too far in and it is doing nothing the standard mirror was not already doing.

2. Fitting to the housing, tight, and checked

Contact against the rigid mirror housing rather than the glass. Clean both faces first. Tension until it does not move when you push it firmly by hand.

Then check it at the first stop. Straps settle and clamps relax on a long run, and a mirror that was solid at the start of a journey is frequently not at the end.

3. Taking them off again

In several countries, driving with extended mirrors fitted and no trailer attached is an offence. They also add width you will forget about in a multi-storey.

Two minutes each way, and part of the routine rather than an afterthought.

4. Checking the rules for your whole route

Requirements differ between countries and are written in terms of the field of view achieved, not the accessory fitted — which is why a rear camera is generally an addition rather than a substitute.

If you are crossing borders, that is the same homework as the rest of the kit: driving abroad: the legal kit.

The rest of the tow, briefly

Mirrors are the visibility half. The load is the other half, and it changes how the car behaves before it changes anything else.

Weight distribution matters more than total weight for stability, and a badly loaded trailer is unstable at speed regardless of what you can see behind it.

How added load changes handling generally is in roof load and how it changes handling, and the argument about restraining a load properly is in bungee cords vs ratchet straps.

The mistake to avoid

Buying them the day before and fitting them in the car park. They need adjusting with the trailer actually attached, from the driving seat, by someone who can walk behind and confirm what is visible. That is a twenty-minute job at home and an unpleasant one on a ferry queue.

The second mistake is treating the vibration as inevitable. It is a fitting symptom. If the image is unreadable at speed, the mirror is on the glass, under-tensioned, or sitting on grit — and all three are fixable in the time it takes to have a coffee.