Tyre Tread depth is one of the most important things to check on your car, it can be the difference between having a safe car that can brake and steer in wet weather, and a dangerous one.

This blog will focus on what the term “tread depth” means, how it’s measured and how it can affect the safety of your car.

What is Tyre Tread and What Does it Do?

Tyre tread is the grooved surface that runs around the perimeter of the tyre, its purpose is to disperse water as the wheel rolls along the road. 

Not having tread would mean the tyres would struggle to get traction, and braking and steering would be extremely difficult, especially in wet conditions. The risk of understeer and aquaplaning would be significantly increased.

What is Tyre Tread Depth?

As the tyres do their job, the forces from accelerating, steering and braking wear away the outer layer of rubber. As the grooves that create the tread are only around 1 cm deep, at some point the tread will be worn away completely, leaving a smooth surface. 

The remaining depth of these grooves is referred to as the Tyre Tread Depth, and there is a legal limit at which the tyres must be changed.

How to Measure Tyre Tread Depth

Keeping track of the wear level of your tyres is something every driver should know how to do. Not only is it dangerous to drive on worn out tyres, but it can land you with some pretty hefty fines too. There are a few ways to check tyre tread depth:

The Simple Tyre Tread Depth Check:

1. Locate a 20 pence coin, notice the slightly raised border all around the coin
2. Put one of the flat edges inside the tread groove of your tyre
3. Check if the tread is deeper than the width of the border around the coin
4. Check each tyre in a couple of places across its width, and all 4 tyres

If your tyre tread is deeper than the border, you don’t need to replace your tyres yet. If the edge of the border is visible, your tread depth is below 3mm and should be replaced soon.

Using a Tyre Tread Depth Gauge:

Tread depth gauges are readily available from car accessory retailers and even most petrol stations or supermarkets. They are basically a small sliding ruler, with an arrow that allows an accurate measurement to be taken. 

Follow the instructions for your particular depth gauge, again measuring each tyre in at least two places, and all tyres on the car - even the spare if you have one.

Using Your Tyres Wear Indicators

As well as the two methods above, a quick and simple method is to check the tyre’s wear indicators or wear bars.

Look for a bar inside the tread grooves, that runs across the width of the tyre. If this bar is level or flush with the outermost tread surface, your tyres need to be replaced. 

Tip: Many tyre brands have a small mark on the sidewall showing where the wear bars are, Michelin has a little Michelin Man symbol, and other brands such as Continental have the letters TWI in line with the bars. 

What is the Legal Tread Depth in the UK?

Tyres with less than 1.6mm of tread are illegal and should be replaced. The general guidance is to replace tyres when they have less than 3mm of tread - this is where the 20p coin trick comes in handy.

H3 What is the Penalty for Worn Tyres?

Driving with tyres worn below the legal limit can result in a fine of up to £2,500, and 3 penalty points, per tyre! That along with the reduced control and braking distance, means keeping on track of your tyre wear is by far the most cost-effective solution.

Why Do You Have To Check Tyre Tread Depth?

We’ve discussed what tyre tread is, and how to check it, but why should you regularly check your tyres?

Tread Depth and Safety

As we’ve touched upon, the link between tyre tread depth and vehicle safety is significant. Tyres need to be able to disperse standing water from puddles, rain or poor road conditions. If they can't, the grip is easily lost.

This can be catastrophic if you need to brake or turn whilst driving on wet roads, worn tyres also make aquaplaning much more likely - this is when your car rides over the surface of standing water rather than pushing it aside, resulting in a total loss of control.

Cost Implications of Not Monitoring Your Tyre Tread Depth

Aside from reducing the likelihood of having an accident, there are other areas where checking your tyres can save you money.

Like any maintenance on your car, being able to plan it in advance can allow you to shop around, finding deals or better places to buy from. Needing tyres urgently is a good way to end up paying a premium for them.

For even more cash flow assistance, use Bumpers zero-interest tyre financing, we’ve partnered with hundreds of tyre garages across the UK, allowing you to spread out the cost.

Further to that, If you’re caught driving on the road on tyres below the legal limit you may well face a significant penalty of up to £2,500 per tyre, as well as an increase to your insurance premiums in future years.