Get a Grip: The Importance of Tires for Vehicle Safety.

Tires are one of the most important parts of your car if not the most important. Tires are the only thing that stay in contact with the ground while driving. They are the medium through which your car translates power from the engine for acceleration, braking forces from the brakes for slowing down, and steering inputs from the steering wheel for turning. Without tires none of these things are possible. That is why keeping your tires in good condition is so important.

Tire Wear, Damage, and Proper Inflation

The first thing we will look at in this section is tire wear. Tires are composed of a compound of mainly rubber mixed with various amounts of carbon, silica, chalk, and oils. Different amounts of these ingredients are added depending on the required uses of the tire. Along with these compounds used for the tire surface there is also steel and nylon cords added to the interior of the tire that help it keep its shape and provides structural rigidity to assist in holding up the weight of the car. As a consequence of being made of rubber tires wear. This is because to provide the best possible grip to the road surface tires must be soft to be able to form to the road surface and have the largest possible contact patch (part of the tire that touches the ground). This is why race car tires have to be changed so often as they are made from extremely soft rubbers to provide as much grip as possible. For normal consumer tires we care more about the longevity of tire use. To help us find tires that will last longer tires are given a “treadwear grade” which tells us how many kilometers a tire will continue to perform how it should. With treadwear grades a higher number means that the tire will last longer under normal operating conditions. Most consumer grade tires will last 60,000 or more kilometers under normal conditions. So, how do you know when your car’s tires have worn down too much and it’s time for a new set? Well, many tires nowadays will have a wear indicator manufactured into them. This typically takes the form of a small, raised portion of rubber within the tire tread. Once the rest of the tire has worn down to that point it’s time to go grab a new set of tires. But what if your tires don’t have this wear indicator? A tire is considered to have worn past it’s safe operating threshold when there is 2/32 of an inch or less tread. An easy way to test if your tires have met this point is to take an American penny and stick the penny into the trough of the tread with the top of Abraham Lincoln’s head pointing towards the tire. If you can see all of Abe’s head, then your tire has worn passed it’s prime and it’s time to get them replaced. There are also tire tread testers on the market which will give you a more accurate reading. But what if your tires are wearing differently all over the surface? That brings us to the next part of this section.

Proper tire inflation. When your tire is not filled correctly either with too much air or too little it will hamper the performance of the tire and can even sometimes put you at risk of experiencing a tire blowout. All tires will have a proper inflation pressure labeled somewhere along the sidewall measured in PSI (pounds per square inch). If your tires are underinflated it will cause your tires to provide less traction causing increased braking distance, worse corning performance, and even hurt fuel economy. Underinflated tires are also more likely to experience a blowout especially at highway speeds which can be very dangerous. If you see that your tires are wearing more on the outside edges of the tread it could be a sign that they are underinflated. Another warning sign is if there is a flat spot on the bottom of the tire when looking at it from the side. If you see either of these symptoms check the pressure and refill if needed. Overinflated tires are also a problem. Just like a balloon, if tires are inflated past their proper pressure, they are more prone to damage and popping (blowing out) like a balloon. Overinflated tires will also cause a harsher ride making it uncomfortable to drive. Like with underinflated tires, overinflated tires do not perform as well as properly inflated tires and your braking and cornering will suffer. A symptom of overinflated tires is a wear patch down the center of your tire’s tread. If you see this check the tire pressure and adjust it if necessary. If you see any abnormal tire wear not mentioned in this section it would be best to bring your vehicle to an alignment shop or a mechanic as most abnormal tire wear can indicate either improper wheel alignment or potentially broken or worn-out components in your suspension/steering system.

To close out this section let’s talk about tire damage. Tire damage can take many forms, most commonly a puncture caused by road debris. Symptoms of this will be low tire pressure and often times you will see the cause of the puncture (a nail, tie down strap, etc.). Another type of damage is sidewall bulging, which is exactly what it sounds like, a bulge in the sidewall of your tire. This is typically caused by hitting a pothole or speedbump at too high a speed and indicates that some of the structural cords within the tire have been broken and the air within the tire is pushing the rubber out at that point. Finally, sometimes you will see cuts or slices on the sidewalls of your tires. These are typically caused by bad road conditions or your tire coming in contact with something sharp. Most often these cuts will cause your tire to deflate. If you encounter any of these problems with your tires you should replace them as soon as possible.

Winter Tires vs. Summer Tires

Picture this: you’re driving through town at night coming home after a night hanging out with friends. It’s winter and the roads are a bit icy. You approach an intersection, and the light turns red. You apply your brakes, but the car doesn’t slow down. You try to apply them again but still nothing happens. You’re in a slide. Your car proceeds through the red light and through the intersection with no signs of slowing down. The reason behind this? You decided that winter tires weren’t worth it, and you kept your summers on. This is a big mistake that many people make but what makes winter tires so much better in the winter and why are they so important?

Firstly, winter tires are manufactured in a different way to summer tires and all-seasons. The rubber in summer tires is designed to work best in temperatures above 5 degrees Celsius. In these temperatures summer tires are able to warm up to their proper operating temperatures and give you the best possible grip on the road. Below 5 degrees, however, summer tires are not able to warm up to the temperatures that allow them to provide the best grip. This causes them to take longer to stop and makes them more likely to lose traction in a corner even in dry conditions. Winter tires, on the other hand, use rubber that is a lot softer. This allows them to operate at much lower temperatures, from 5 degrees all the way down to the high negatives. The ability to stay pliable and “sticky” in these low temperatures means that winter tires are able to have better traction, shortening stopping distances and providing better grip through corners than summer tires or even their all-season counterparts.

There is also a big difference in tread patterns between summer and winter tires. Summer tires will typically have shallow grooves in the tread with lines that are smoother. These tread designs are very well suited to providing grip in warmer weather especially on dry roads. However, they don’t provide adequate expulsion of snow and ice, and will build up a layer of snow which will act as a slick surface allowing the tire to slide across the road surface. In addition, the smooth, skinny treads are not able to dig into and grip the ice or snow surface causing the tires to be more prone to slipping while accelerating. Winter tires, on the other hand, had much deeper and wider grooves in the tread; allowing for superior snow expulsion which prevents a build up of snow and ice on the surface of the tire as seen on the summer tires. The tread design on winter tires is also very different to that of the summer tires, being more jagged and sharp with irregular edges. This allows the tire to dig and bite into a snow- and ice-covered road surface providing superior traction. Winter tires also have small sipes all over the surface of the tire that meets the road. Sipes are small cuts in the tread that provide an additional biting and gripping force on icy road surfaces. Some winter tires will even have crushed up walnut shells added to the rubber of the tread to provide even more of a biting effect on icy roads.

These differentiations are well and good but what are the real-world differences between summer tires and winter tires in winter driving conditions. There have been many tests done to show the differences and benefits of using winter tires in winter driving conditions but we will be using the test conducted by tirerack.com to provide our data. TireRack(TR) used a 2008 BMW E92 328i Coupe for their test and used 3 different sets of tires, a set of winter tires, all-season tires, and summer tires. For our uses we will be focusing on the winter and summer tires. All these tests were performed on an ice rink to simulate icy road conditions. The first test was time to accelerate to 60 feet from a stop. With the summer tires fitted to the test car it took 7.4 seconds for the car to travel the 60 feet. With the winter tires fitted it took the car 4.5 seconds to travel that same distance. That is a difference of 2.9 seconds. The next test involved distance to come to a complete stop from 10 miles per hour. A similar scenario to what we talked about in the start of this post. The summer tires required 47 feet to come to a complete stop with the anti lock brake system activating the entire time. To put that into perspective that is almost the entire length of a semi truck trailer. With the winter tires fitted, the car only took 21 feet to stop. Less than half the distance the summer tires required! A difference of 26 feet! The final test had the car attempt a 90-degree corner at a speed of 10 miles per hour. A situation you would often find while driving through urban areas. With the summer tires fitted the car began to slide almost immediately when the corner was attempted. The car proceeded to slide through the cones setup on the outside of the corner and even hit the boards at the end of the rink. Attempting the same corner on winter tires had a drastically different outcome. The car completed the corner with no indication of sliding and did not hit any of the cones. These tests being performed on an ice rink may be a bit more extreme than the conditions that some of us may face while driving out on the roads. But, living in Canada there is always the possibility of encountering these conditions at least a few times per year. These tests show just how important it is to have winter tires fitted during the cold winter months. The difference in performance in a controlled environment like this hockey rink may present as just numbers but if you transfer the data into real world scenarios you get a much different picture. The 26 foot difference in stopping power could be the difference between stopping safely at a red light or sliding into the intersection while cross traffic is coming through. The ability to make corners while maintaining grip instead of sliding through the corner may be the difference between driving around a bend without incident or sliding into a guard rail or oncoming traffic. These situations aren’t meant to scare you. They are merely examples of what could happen if you don’t have tires properly suited to the conditions.

Hopefully, after reading this you’ve been convinced that switching over to winter tires during the colder months is not just the responsible thing to do, it has the potential to save your life and the lives of other people.

Conclusion

In conclusion, tires are very important to the safety and performance of your vehicle and whether you’re maintaining your tires or choosing the right tires for the conditions it is important to be educated on the factors that affect them. Hopefully this post has given you some answers to questions you may have had about tires and will allow you to be more confident on the road knowing that you have a good connection with the road.

Written by: Liam McMillan