What's the minimum depth of tread on trailer tyres?

Have you ever wondered what's the minimum depth of tread on the tyres of a trailer? Would the same legal requirements for car tyres apply to trailers, or is it enough to keep them in decent running condition?

UK law requires that tyres for cars, goods vehicles weighing less than 3,500 kg, and trailers have at least 1.6 mm of tread depth throughout a continuous band around their circumference. Failure to meet this requirement, even on your trailer, can result in a monetary fine and penalty points on your licence.

In this article, we’ll discuss why it’s important to know the minimum depth of tread on the tyres of a trailer. We’ll talk about the different ways you can measure tread depth and what to do once it goes below the legal requirement. We’ll also explore how tyre tread depth helps keep you on the road safely.

What are the rules for trailer tyres in the UK?

Trailer tyres are subject to the same rules that cars and other vehicles must follow. Before bringing your trailer along with you on your next trip, make sure your tyres meet the following requirements:

• Not have any lumps, bulges, or other structural defects
• Be inflated with the correct tyre pressure according to manufacturer standards
• Not have a cut or tear longer than 25 mm or 10% of the tyre’s width, whichever is greater
• No cuts, tears, or other damage deep enough to reach the tyre’s cords
• Be the proper size for your trailer and its expected load
• Be less than 10 years old from the tyre’s manufacturing date
• Have a minimum tread depth of 1.6 mm in a continuous band around the tyre

Towing a trailer with tyres that don’t meet the legal requirements could lead to a fine of up to £2,500 and 3 points on your licence per tyre. Your insurance provider could also invalidate your claim if you were involved in an accident with faulty tyres.

What is the legal minimum tyre tread depth?

The UK's legal minimum tyre tread depth differs slightly depending on your vehicle:

Legal minimum tread depth of at least 1.6 mm in a continuous band around the circumference of the tyre, extending at least three-quarters of the central tread:

• Cars and other passenger vehicles that carry no more than eight passengers, aside from the driver
• Goods vehicles with a maximum gross weight of 3,500kg or less
• Light trailers with a maximum gross weight of 3,500kg or less

Legal minimum tread depth of at least 1 mm in a continuous band around the circumference of the tyre, extending at least three-quarters of the breadth of the tread. You must be able to see the tread pattern in the remaining quarter of its width:

• Vehicles heavier than 3,500kg
• Passenger vehicles designed to carry more than eight passengers
• Motorcycles over 50cc

Being able to see the original tread pattern:

• Mopeds and motorcycles under 50cc

Source: Ask the Police

What if my trailer tyres don’t meet the legal minimum tread depth?

If one or more of your trailer tyres don’t meet the legal minimum tread depth, you must replace them immediately. Towing a trailer with a bald tyre is illegal and could lead to a £2,500 fine and 3 points on your licence. Remember that these penalties are per tyre, which means you could be disqualified from driving if your trailer has four illegal tyres.

Using a tyre with less than the legal minimum tread depth is also hazardous to you and other road users. Worn tyres could cause:

• Less grip on the road, especially when wet
• Higher risk of aquaplaning (loss of traction due to a layer of water between the tyres and the road surface)
• Higher risk of punctures, which could cause a blowout

How to measure trailer tyre tread depth

There are three ways you can measure your tyre’s tread depth:

• With a tyre tread depth gauge: Tyre tread depth gauges are easy-to-use tools that immediately tell you how much tread depth you have. They come in different forms: digital, analogue, or laminated cards with indicators. Place your tool on the tread groove to get a measurement.
• Using a 20p coin: Though not an accurate way of measuring tread depth, a 20p coin can still help you check your tyre quickly. That’s because the outer band of the coin measures just under 3 mm. Place the coin on your tyre’s groove (with the coin facing you) and observe whether you can see the outer band.
  • If you don’t see the outer band, you still have at least 3 mm tread depth left.
  • If you can partially see the coin’s outer band, it may be time for a closer check with a gauge. You may be close to the 1.6 mm tread depth limit.
  • If you can see the entire coin, it’s time to replace your tyre.
• Checking your tyre’s tread wear indicators: Most manufacturers embed an indicator on the tyre to help you determine when it’s time to change it. The indicator is usually a line or an arrow, and you’ll find it somewhere along the outer tread. If the tread is level with the indicator, your tyre will need to be replaced.

What tread depth should I change my trailer tyres?

The legal minimum tread depth for trailer tyres is 1.6 mm; any tyre below this threshold must be replaced with a newer one.

However, most tyre manufacturers and safety experts recommend changing your tyres once they reach a tread depth of 2-3 mm. Waiting until the tread depth reaches below 2 mm could put you at risk of going below the legal minimum of 1.6 mm.

If you’re unsure whether your tyre needs replacing or not, have a reputable garage or tyre fitter take a look for you. They can advise you about the condition of your trailer tyres.

Why is the minimum depth of tread for trailer tyres important?

Staying above the minimum depth of tread for trailer tyres keeps you and other road users safe.

According to a 2003 study commissioned by the British Rubber Manufacturers Association, a tyre with a 1.6 mm tread depth needs 44.6% more stopping distance on smooth concrete than one with a 3 mm tread. On hot asphalt roads, the difference is 36.8 per cent.

Staying above the recommended 2-3 mm tread depth can also reduce the risk of:

• Aquaplaning occurs when a layer of water buildup between the tyre and the road surface reduces traction. Loss of traction compromises trailer handling, putting you and other motorists in danger.
• Punctures
• Less traction during icy, snowy, or wet weather conditions
• Loss of control due to compromised handling
• Tyre failure

In summary

The legal minimum tread depth for trailer tyres is 1.6 mm, which is the same requirement as cars. This measurement must be continuous around the tyre, extending at least three-quarters from the central tread. Towing a trailer with bald tyres is illegal and could result in a £2,500 fine and 3 points on your licence for each offending tyre. It could also get your insurance claim invalidated in case of an accident.

Although 1.6 mm is the legal minimum, most manufacturers and safety experts recommend changing your trailer’s tyres once the tread depth measures 3 mm. Waiting until it reaches close to 2 mm could be hazardous and puts you at risk of going below 1.6 mm.

You can use a tread depth gauge, a 20p coin, or the tread wear indicator to measure your trailer tyre's tread depth. Using a 20p coin can be helpful for a quick check without a tread depth gauge, as the coin’s outer band is just under 3 mm. If you can’t see the coin’s outer band when you place it in the tread, you still have over 3 mm of tread left.

Frequently Asked Questions

Do trailer tyres have different minimum tread depth than cars?

Tyres used for trailers are subject to the same legal standards as car tyres. That means trailer tyres must have a minimum tread depth of 1.6 mm in a continuous band before they must be replaced. Driving a bald tyre (with little to no tread left) is illegal and dangerous.

Is a 3 mm tyre tread ok?

A 3 mm tyre tread is still acceptable, but it’s recommended that you change the tyre soon. Going below 3 mm of tread affects your tyre’s stopping distance, which could affect handling with towing.

Is 2 mm tyre tread legal?

A trailer tyre tread of 2 mm is legal, as it is above the 1.6 mm minimum. However, it’s recommended that you change the tyre soon so that the tread depth doesn’t fall below the legal requirement.

What tread depth do brand-new tyres have?

Brand-new tyres start with approximately 8 mm of tread depth. How quickly the tread wears off depends on how often you use your trailer, where you store your trailer when you’re not using it, and your trailer load weight.

Can I still use a tyre with 1 mm tread depth?

It’s illegal to use a tyre with 1 mm tread depth because the legal minimum is 1.6 mm. If your trailer tyre has 1 mm of tread depth left, you must replace it before towing it. Otherwise, you’ll be subject to a £2,500 fine and 3 points on your licence per tyre.

Also read:

• Is buying a caravan worth the cost?
• Do you need insurance to tow a caravan?
• Top Ten Caravan Towing Cars
• How should you load your trailer?
• READ MORE OF OUR CARAVAN INSURANCE GUIDES

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