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Driving on bald tires is one of the most dangerous things you can possibly do. According to the Crash Causation Survey of the NHTSA, more than 9 percent of vehicular crashes started with problems in the tires and while the tire-related issues included a variety of factors, bald tires are definitely one of them. Now you may think that 9 percent is almost negligible, but accidents happen and you’ll never know when you’ll suddenly find yourself part of the 9%. As a rule of thumb, if your tire’s tread wear indicators show that it’s time to have it replaced, then, by all means, go for a tire change. If not, you’ll only be risking becoming just another statistic to the incidence of vehicle collisions in major roads.

The Dangers of Driving on Bald Tires

The tires of your vehicle are actually what is keeping it on the road. The National Highway Traffic Safety Administration says that of all the vehicle collisions occurring in America’s roads, close to 10 percent of them are related to issues with the tires, including bald tires. Here are some of the more common dangers of driving on bald tires.

  • Increased risk of tire failure even on dry roads

The available traction on the tires has always been an important safety issue especially on highways and on wet roads.

While it is true that the impact of tire tread depths on vehicle safety on dry roads and highway speeds is minimal, it is still possible to cause tire blowouts. This is because a reduction in tire tread depth also means thinning of the tire structure itself. This makes it relatively easy to puncture. Additionally, if inflated to a much higher pressure than recommended, this can cause the tire to burst causing tire failure and a disastrous consequence for the occupants of the vehicle.

  • Increased risk of hydroplaning and loss of vehicle control in wet conditions

As mentioned above, tire traction is tantamount to road safety especially if you’re driving on wet roads. The tread pattern on the tires help to channel surface water away from the contact patch and this is assisted by the depth of the treads. If the treads are shallow the tire may not be able to effectively displace surface water. As you know, there is surface tension in water which somehow creates a thin layer of water bands under the contact patch of the tire. This effectively increases the distance between the ground surface and the tire.

Technically, the tire 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 tires will try to grab onto the water bands, creating hydroplaning or simply skidding. Tests show that bald tires will increase your stopping distance by at least twice while also reducing optimum control of the vehicle in wet road conditions.

  • Increased risk of skidding in icy and snowy conditions

Driving on snow with bald tires can also lead to loss of vehicle control. Snow tires often come with sipes that immensely improve traction over snowy and icy road conditions. However, as tire tread depth decreases, so do these sipes. You are essentially at the mercy of momentum as the slippery surface of ice can really make your vehicle slide along the surface even if your brakes have been pushed to the limit.

  • Loss of tire pressure

It is a well-known observation that bald tires lose their pressure a lot faster than those with sufficient tread depth. While it is perfectly okay to check tire pressures on a daily basis, at the end of the day you may already have an underinflated tire. This can lead to a host of problems such as reduced control of your vehicle, reduced fuel efficiency, and issues in braking. All of these will contribute to faster wear of your tires.

  • Unsafe heat buildup

The thickness of the tire treads actually works to help prevent massive heat buildup as the tires are in constant contact with the road. It is the function of the treads to allow air to be channeled through the grooves and cool your tires. However, with shallow treads, this airflow is also reduced which can lead to substantial overheating in the tire. This can lead to blowouts.

How Do You Know If You Already Need to Replace Your Tire?

Modern tires typically come with tire tread wear indicator bars. This is a thin band of rubber that is embedded across the tread area of your tire. Normally, you won’t see these bars especially if your tires are relatively new. That’s the beauty of it. Once they become visible you’ll know that your tire has reached its end of the line. You definitely want to start planning for purchasing a new set.

Inserting a penny into the tire tread with Abraham Lincoln’s head inserted first can also be a rough measure of your tire’s tread depth. What you want is the level of the contact patch to be covering the hairline or forehead of Abe. If the tread is in line with the top of his head, you’ll definitely need a new tire. This is the minimum requirement, of course. A much better and safer recourse is to use a quarter to measure the tread depth. Again, you’d want the tread to at least cover the hairline of George Washington; otherwise, a new tire is in the offing.

It is also important to inspect the tire’s sidewalls especially for signs of cracks, blisters, or bulges. The latter two can be a serious concern since these are largely considered weak spots in the tire. They can lead to blowouts and loss of vehicle control. In some cases, they can also contribute to hydroplaning and skidding. As such, if you see blistering and/or bulging in your tires, it’s imperative that you get to a tire shop immediately.

Tire Laws in the UK

In the UK, motorists are required to use only the correct size and type of tire for their respective vehicles. Also, the purpose for which the vehicle is to be used should also be taken into consideration when choosing the type of tire. For instance, going on off-road adventures will require certain tire 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 tires should be changed accordingly, lest you earn a penalty from the government.

When it comes to the minimum tread depth, the UK government places this at 1.6 millimeters measured on the central three-quarters of the width of the tread area. And the measurement should be taken throughout the entire circumference of the tire. This is generally for cars, goods vehicles, caravans, and trailers that weigh less than 3,500 kilograms. For larger vehicles, the minimum tire tread depth is smaller at 1.0 millimeter. However, the original tread pattern of the tire must still be clearly visible on the remaining ¼ of the tire tread area. The same is true for motorcycles with engine displacements of 50 cc and above. For motorcycles and mopeds with less than 50 cc engine displacement, there are no minimal tire tread depths except for the visibility of the original tire tread pattern.

Failure to comply with the minimum tire tread requirement will earn you 3 penalty points on top of a £2,500 fine for having tires that are worn beyond the minimum legal requirement.

The current recommendation is that tires should be replaced before reaching the legal minimum tire tread limit. Most tire manufacturers strongly recommend replacing or changing the tires once the tread depth has reached 3 millimeters. This is to compensate for wet weather conditions. Studies show that running your vehicle with tires at the minimum legal tire tread depth of 1.6 will require an additional 8 meters, equivalent to the length of about 2 cars, to come to a complete stop when going at 50 miles per hour. Running on tires with minimum tire tread depth of 3 millimeters 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 tire tread depth, it is also important to never put different tire constructions in the same axle. For instance, if you have radial tires make sure that both tires 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 tire brands and patterns on the same axle, just make sure that they comply with the manufacturer’s recommendation as well as your type of vehicle.

For some interesting facts and further things you wish to know about driving on bald tires, this excellent safety film from Confused.com is a great resource.

Tire Laws in the US

While UK motorists enjoy the benefit of having a centrally-regulated tire tread depth limits, tire laws in the US are quite mixed. Currently, there are no federal laws that provide for specific guidelines on what can be considered as the minimum safe tire tread depth of vehicles. This is left mostly to the different states in the country.

Most states in the US put the legal minimum tire tread depth at 2/32nd or 1/16th of an inch. In California and Idaho, however, the minimum is placed at 1/32nd of an inch while Arkansas, West Virginia, South Carolina, New Mexico, Montana, and North Dakota do not have any specific regulations or standards on what can be considered as the minimum safe tread depth of tires.

American Consumer Reports, however, actually places the recommended tire tread depth at 4/32nd or 1/8th of an inch. Just like in the UK, the adjustment in the minimum tire tread depth is based on compensation models for wet driving conditions. The tires 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 tires is too shallow (say, 1/32nd of an inch or 2/32nd of an inch) there’s a possibility that water will not be channeled properly to the outer sides of the tires.

This was confirmed by a field test regarding the effective stopping distances of different tire 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 tire tread depth of 2/32nd of an inch double their stopping distances. For example, on a set of brand new tires, the car will stop after 50 feet. With the tire tread depth at the legal minimum, the stopping distance will be 100 feet. The 50-foot difference can really mean a lot in terms of vehicle and passenger safety.

American motorists are always taught to perform the penny test on their tire treads. If the level of the tread is in line with Abraham Lincoln’s head, that means you’re at the 2/32-inch limit and it would be wise to have your tires changed. If the tire depth is in line with Abe’s forehead, you still have quite some room to go, but you’ll expect to change your tire soon.

If you’re adhering to the current recommendation of 4/32-inch, then you’d need a quarter for that. In the same manner, insert George Washington head first into your tire tread. If it is in level with his hairline you’re basically up for a tire change soon.

Tire manufacturers usually design their tires with tread depths ranging from 10/32nd of an inch to 11/32nd of an inch. This usually lasts about 6 to 10 years, depending on how the vehicle is used and other factors that may affect the rate of change in the tire tread depth.

Keeping the integrity of your tires is tantamount to improving the road-worthiness of your vehicle. While tire tread depth is just one of several factors you really have to keep in mind whenever driving your vehicle, it remains one of the most important parameters for improving road safety.

Sources

  1. Damaged or Worn Tyres Endanger Lives, Automobile Association
  2. 5 Reasons Why Driving on Worn Out Tire Can Be Dangerous, Fix Auto USA
  3. What is Safe Tire Tread?, Driver’s Prep US

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