Tyre Tread Depth: How To Check, Legal Limit & Advice
Your car tyres are the only part of your vehicle that is in contact with the surface of the road. This alone is enough to highlight the importance of ensuring they are in the best condition they can be, to ensure your and your passenger's safety.
In addition to the safety risks, ignoring the condition of your tyres for too long can land you a fine of £2,500 per tyre. So, if all four of your tyre's tread are below the legal limit, you risk a fine of £10,000 and could potentially lose your license.
To sum it up, if you're caught driving with illegal or “bald” tyres, you could face:
- A fine of up to £2,500 per tyre
- Three points per tyre on your licence, which will result in disqualification
- If you make an insurance claim this can become invalid.
In this short guide, we'll break down the importance of tread depth, how you can check it and how often you should check your tyre tread.
What is the legal tyre tread depth in the UK?
The legal tyre tread depth in the UK is 1.6mm across the central three-quarters of the tyre. The tyres' tread must meet this minimum depth requirement across its entire circumference according to the law.
RoSPA Tread Depth Recommendations
RoSPA, The Royal Society for the Prevention of Accidents recommends changing the tyre once the tread level wears down to 3mm. This is 1.4mm above the legal minimum but is based on various studies conducted into tread depth and the impact it can have on road safety.
How to measure your tyre tread depth
So now you know what depth your tyres legally need to be, let's look at three quick and easy ways you can check your tyre tread depth.
Using tyre tread wear indicators
For a quick visual check, you can simply look at the wear indicators on the tyre. To find these just look at grooves of the tyre tread. If you can clearly see these on your tyres, it's very likely they are below the legal minimum tread depth and will need replacing immediately.
Using a tyre tread depth gauge
Tread depth gauges are purpose tools you can easily store in your glove box. They will provide a much more accurate and reliable way to measure your tyre’s tread depths.
The 20p check
The 20p test is the quickest and easiest way you can check your tread depth right now but it's worth noting it's also the least accurate.
How to do the 20p test:
- Get a 20p coin and place it into the main tread grooves of the tyre.
- If you can’t see the raised ridges around the 20p, the tyre tread is likely above the 1.6mm legal limit.
- However, if you can see the outer band when the 20p is in the tyre grooves, your tyre is likely to be below the 1.6mm legal limit and will require replacing.
Be sure to do this test across the central three-quarters of the tyres as alignment and other factors can cause your tyre tread to wear unevenly.
Tyre tread depth chart
The below chart illustrates the condition of your tyres in relation to the amount of tread left. Once your tyres reach around 3mm you will need to keep a close on them. At this level they will not be performing optimally and will quickly wear down to the legal limit.
Why is tyre tread depth important?
As we mentioned before, your tyres are the only thing between your vehicle and the road surface, so they play a vital role in keeping you safe. Tread depth is important for two main reasons:
Keeps stopping distances short
There have been quite a few studies that support the link between low tread and a reduction in tyre braking performance. One of the most comprehensive was carried out by the British Rubber Manufacturers Association and MIRA.
The test was carried out on MIRA's test track in Nuneaton and looked at the performance of five tyres with different tread depths ranging from 6.7mm to 0.9mm. They found that stopping distances increased significantly once tread levels were below 3mm. It got even worse at the legal limit of 1.6mm.
At 1.6mm vehicles stopping distance increased by 44.6 percent compared with a tread depth of 6.7mm.
So, this clearly demonstrates the need to check your tyres regularly for any cults or bulges and the tyre's tread level. If you suddenly need to stop to avoid a collision the consequences could be very serious if your braking distance is increased.
Reduces the risk of aquaplaning
If your vehicle is running on low or illegal tyre tread depths this increases the risk of aquaplaning. This happens when a layer of water is built up between the road surface and your tyres. This causes a loss of traction that reduces the effectiveness of braking and drastically limits the handling of the vehicle.
Tread grooves are carefully and specifically designed to help disperse water as the tyre makes contact with the road. As these groves wear down, they become less effective at doing this. This can be extremely dangerous in wet weather conditions where you are travelling at high speeds.
The tread in tyres is carefully designed to help disperse water.
As the grooves become less pronounced, however, their ability to do this effectively is reduced. Aquaplaning can be a very scary experience and, particularly if you are travelling at speed and there is a lot of water on the road, it can be extremely dangerous.
So simply put, the more tread you have on your tyres the better they will be handling wet road surfaces and the less likely you will be to lose traction in wet conditions.
That's why it is always essential to check tread wear indicators on your car tyres before long journeys to ensure you have the legal limit of 1.6mm.
How often should I check my tyre tread?
Driving in the UK means you'll likely have to drive in adverse weather conditions on a regular basis, and as such it's vital you check your tyres regularly as well.
Carrying out basic but essential tyre checks can reduce potential issues you might face. This could include anything from preventing delays and additional expense to dangerous cases of injury.
ATS Euromaster technicians would recommend checking your tyres once every couple of weeks and at least once a month. We also recommend checking your tyre tread depth before long journeys to minimise the risk of tyre related accidents.
What causes tyre wear?
When you have new tyres fitted on your car these will come with approximately 8mm of tread, but naturally, as you begin to drive around on the tyre, wear and tear occur and this gradually becomes shallower over time.
How quickly your tyres reach the minimum tread depth will depend on a few things:
- The type of vehicle you drive
- The type of journeys you make (motorway vs local)
- Your driving style
- The quality of the tyre
- Poorly inflated tyres
- Improper wheel alignment
How long your tyres last will be influenced by a combination of the factors above. Whilst you may be tempted to wait until you legally need to replace your tyres it is also widely accepted and advised to replace your tyres when they get to 3mm of tread left.