Driving on bald tyres is one of the most dangerous things you can do. According to the Crash Causation Survey of the NHTSA, more than 9 per cent of vehicular crashes started with tyre problems. While tire-related issues include a variety of factors, bald tyres are one of them, leading to increased risk of punctures, reduced grip, longer stopping distances, and potential accidents. Now, you may think that 9 per cent is almost negligible, but accidents happen, and you’ll never know when you’ll suddenly find part of the 9%. Driving with bald tyres can also result in legal penalties, including fines and penalty points on your driving licence. As a rule of thumb, if your tyre’s tread wear indicators show that it’s time to have it replaced, then, by all means, go for a tyre change. If not, you’ll only risk becoming just another statistic to the incidence of vehicle collisions on major roads.
The Dangers of Driving on Bald Tyres Dangerous
The tyres of your vehicle are actually what keeps it on the road. The National Highway Traffic Safety Administration says that of all the vehicle collisions occurring on America’s roads, close to 10 per cent are related to issues with the tyres, including defective tyres. Here are some of the more common dangers of driving on bald tyres.
Increased risk of tyre failure even on dry roads
The available traction on the tyres has always been a significant safety issue, especially on highways and wet roads.
While it is true that tyre tread depths have a minimal impact on vehicle safety on dry roads and highway speeds, it is still possible to cause tyre blowouts. Reducing tyre tread depth also means thinning the tyre structure itself, which makes it relatively easy to puncture. Additionally, inflating to a much higher pressure than recommended can cause the tyre to burst, causing tyre failure and a disastrous consequence for the vehicle’s occupants.
Increased risk of hydroplaning and loss of vehicle control in wet conditions
As mentioned above, tyre traction is equivalent to road safety, especially when driving on wet roads. The tread pattern on the tyres helps channel surface water away from the contact patch, and the treads’ depth assists in this. If the treads are shallow, the tyre may be unable to displace surface water effectively. As you know, surface tension in water creates a thin layer of water bands under the tyre’s contact patch. This effectively increases the distance between the ground surface and the tyre.
Technically, the tyre is in contact with the water, not the road surface. If you apply the brakes, there is no firm surface to hold onto. Instead, the tyres will try to grab onto the water bands, creating hydroplaning or simply skidding. Tests show that bald tyres will increase your stopping distance by at least twice while reducing the vehicle’s optimum control in wet road conditions.
Increased risk of skidding in icy and snowy conditions
Driving on snow with bald tyres can also lead to losing vehicle control. Snow tyres often come with sipes that improve traction over snowy and icy road conditions. However, as tyre tread depth decreases, so do these sipes. You are essentially at the mercy of momentum, as the slippery surface of ice can make your vehicle slide along the surface even if your brakes have been pushed to the limit.
Loss of tyre pressure
It is a well-known observation that bald tires lose their pressure much faster than those with sufficient tread depth. While it is perfectly okay to check tyre pressures on a daily basis, you may already have an underinflated tyre. This can lead to a host of problems, such as reduced vehicle control, reduced fuel efficiency, and issues in braking. All of these will contribute to faster tyre wear.
Unsafe heat buildup
The tyre treads’ thickness helps prevent massive heat buildup as the tyres are in constant contact with the road. The treads allow air to be channelled through the grooves and cool your tyres. However, this airflow is also reduced with shallow treads, leading to substantial overheating in the tyre and blowouts.
How Do You Know If You Already Need to Replace Your Tire? Check Tyre Tread Depth
Modern tyres typically come with tyre tread wear indicator bars. This is a thin band of rubber that is embedded across the tread area of your tyre. Usually, you won’t see these bars, especially if your tyres are relatively new. That’s the beauty of it. Once they become visible, you’ll know your tyre has reached the end of the line. You want to start planning for purchasing a new set.
Inserting a penny into the tyre tread with Abraham Lincoln’s head inserted first can also be a rough measure of your tyre’s tread depth. What you want is the level of the contact patch to cover Abe’s hairline or forehead. If the tread aligns with the top of his head, you’ll need a new tyre. This is the minimum requirement, of course. Using a quarter to measure the tread depth is a much better and safer resource. Again, you’d want the tread to at least cover George Washington’s hairline; otherwise, a new tyre is needed for the offing. Alternatively, using a tyre tread depth gauge is a more accurate method to measure the depth of individual tyre grooves.
Inspecting the tyre’s sidewalls is also essential, especially for signs of cracks, blisters, or bulges. The latter two can be a severe concern since these are considered mainly weak spots in the tyre. They can lead to blowouts and loss of vehicle control. In some cases, they can also contribute to hydroplaning and skidding. If you see blistering and bulging in your tyres, you must get to a tyre shop immediately. Before long journeys, it is crucial to use a tyre tread depth gauge to ensure your tyres are safe and roadworthy.
To check tread depth using the 20p coin test, insert the coin into the tread grooves. If the outer band of the coin is visible, it indicates that the tyre tread depth is below the legal limit, and you should consider getting a new tyre or a professional inspection.
Minimum Tread Depth and Tire Laws in the UK
In the UK, motorists are required to use only the correct size and type of tyre for their respective vehicles. Also, the purpose for which the car is to be used should be considered when choosing the type of tyre. For instance, going on off-road adventures will require specific tyre characteristics that will allow the vehicle to improve its traction on rough, uneven terrain. The same is true when carrying heavier loads than usual. The vehicle’s tyres should be changed accordingly, lest you earn a bald tyre fine from the government.
Regarding the legal minimum tread depth, the UK government places this at 1.6 millimetres measured on the central three-quarters of the width of the tread area. The measurement should be taken throughout the entire circumference of the tyre. This is generally for cars, goods vehicles, caravans, and trailers that weigh less than 3,500 kilograms. The minimum tyre tread depth for larger vehicles is smaller at 1.0 millimetres. However, the original tread pattern of the tyre must still be visible on the remaining ¼ of the tread area. The same applies to motorcycles with engine displacements of 50 cc and above. For motorcycles and mopeds with less than 50 cc engine displacement, there are no minimal tyre tread depths except for the visibility of the original tyre tread pattern.
Failure to comply with the minimum tyre tread requirement will earn you three penalty points on top of a £2,500 fine for having tyres worn beyond the minimum legal requirement.
The current recommendation is to replace tyres before the legal minimum tyre tread limit is reached. Most tyre manufacturers strongly recommend replacing or changing the tyres once the tread depth has reached 3 millimetres. This is to compensate for wet weather conditions. Studies show that running your vehicle with tyres at the minimum legal tyre tread depth of 1.6 will require an additional 8 meters, equivalent to the length of about two cars, to come to a complete stop when going at 50 miles per hour. Running on tyres with a minimum tread depth of 3 millimetres will help improve traction on the wet road surface, allowing you to come to a complete stop within the expected stopping distance of the vehicle.
Aside from the minimum tyre tread depth, it is also important to never put different tyre constructions in the same axle. For instance, if you have radial tyres, ensure that both tyres on the opposite ends of the same axle are of radial construction. You don’t put a radial on one end and a cross-ply on the other. However, you can mix different tyre brands and patterns on the same axle and ensure they comply with the manufacturer’s recommendation and your type of vehicle.
This excellent safety film from Confused.com is a great resource for some interesting facts and other things you wish to know about driving on bald tyres.
Tire Laws in the US: Bald Tyre Fine
While UK motorists enjoy having centrally-regulated tread depth limits, tyre laws in the US are pretty mixed. Currently, no federal laws provide specific guidelines on what can be considered the minimum safe tread depth of car tyres. This is mainly left to the different states in the country.
Most states in the US set the legal minimum tire tread depth at 2/32nd or 1/16th of an inch. In California and Idaho, however, the minimum is set at 1/32nd of an inch. Arkansas, West Virginia, South Carolina, New Mexico, Montana, and North Dakota do not have any specific regulations or standards for what is considered the minimum safe tread depth of tyres.
It is crucial to check car tyres regularly to ensure safety while driving and to comply with legal requirements.
American Consumer Reports, however, actually places the recommended tyre tread depth at 4/32nd or 1/8th of an inch. Like in the UK, the minimum tyre tread depth adjustment is based on compensation models for wet driving conditions. The tyres need to maintain contact with the solid surface of the road and not on the water that has collected on the surface. This is to prevent hydroplaning. If the depth of the tyres is too shallow (say, 1/32nd of an inch or 2/32nd of an inch), water may not be appropriately channelled to the outer sides of the tyres.
This was confirmed by a field test regarding the adequate stopping distances of different tyre tread depths on roads with minimal water pooling on the surface. The tests revealed that, at 55 miles per hour, cars with the legal minimum tyre tread depth of 2/32nd of an inch double their stopping distances. For example, the car will stop after 50 feet on brand-new tyres. With the tyre tread depth at the legal minimum, the stopping distance will be 100 feet. The 50-foot difference can mean a lot regarding vehicle and passenger safety.