The surprising (but unspoken) way tyres affect braking

The surprising (but unspoken) way tyres affect braking

Thought brakes are the only thing that affects how quickly your car slows down? Think again. Your tyres play an equally crucial role.

Brakes are the one component on a car that contributes most to safety. For all the airbags or advanced active safety tech in the world, when it comes down to it, avoiding an accident is largely dependent on slowing down in time. With that, it’s easy to understand why drivers might think upgrading their car’s braking performance is important.

Yet, it’s a misconception that throwing on a big brake kit, enlarged callipers or higher-friction brake pads will automatically result in better stopping distances; a car’s tyres actually have a huge role to play as well.

Of course, if you have a Bugatti Chiron, massive brakes and sticky tyres come as standard

To see what we mean, try this: run along the sidewalk wearing a new pair of shoes, then come to a stop as fast as possible. Repeat with a pair of extremely worn out shoes. Notice the difference?

Now do the same two tests on a wet sidewalk. Notice even more difference?

It’s exactly the same case with tyres. The more grippy a set of tyres, the more brake force that can be transmitted via the tyres to the road. If your tyres don’t have grip, all that extra braking force is wasted as the tyres will want to lock up.

The shortest possible braking distance is dependent on the tyres, while still spinning, being held at their threshold of locking up. Once locked up, the tyres will simply slide. This is where anti-lock braking systems or ABS come into play.

How ABS works

In simple terms, ABS utilizes sensors in each wheel to monitor tyre lock-up. When a tyre starts to lock up, ABS pulses the respective brake to release the tyre from a locked up state to rotating again, and does this multiple times per second.

ABS warning light

By looking at the way ABS works, we can better comprehend that peak braking efficiency happens right before a tyre locks up, or what is known in the industry as braking threshold.

Contrary to popular belief, ABS actually increases a car’s braking distance as compared to skilful threshold braking, because the tyres repeatedly alternate between being locked up and rolling again all the way until the car comes to a stop.

However, with skilful threshold braking, the tyres are actually held at maximum braking grip with the road, resulting in a shorter braking distance. Thing is, maximum threshold braking is extremely difficult to achieve even in controlled ideal conditions, let alone in the unpredictability of real-world driving. Hence, for most of us mere mortals, ABS does shorten braking distances as compared to a car sliding on completely locked up tyres; not to mention allowing us to retain some ability to steer the car while fully braking.

In other words, the later we can make ABS activate, the shorter the distance a car would need to come to a halt.

Tyre grip vs braking distance

When a tyre has decreased grip with the road owing to wear, the braking threshold is lower, causing ABS to activate earlier also. With a new, grippier set of tyres, the braking threshold would be reached later.

This is also true for a grippier compound of tyres, such as high-performance or ultra-high performance ones, as opposed to something comfort or eco oriented.

With UHP tyres like this Yokohama Advan AD08R, better braking performance is guaranteed

Most people would tend to look at upgrading brake pads to improve braking performance. However, this may not always be beneficial.

An upgraded set of brake pads needs grippier tyres to perform to their fullest. Otherwise, the upgraded pads would just overwhelm the grip offered by the tyres sooner, causing ABS to cut in earlier, leading to longer braking distances anyway. A simple way to test if the existing set of brake pads is adequate is to do an emergency stop on a deserted road. If ABS cuts in, then the brake pads do not need to be upgraded.

AUTA’s braking tests simulate full-bore emergency stops from highway speeds

But does this mean that one should necessarily upgrade to high-performance or ultra-high performance tyres?

No. Use-case must be considered.

However, the age and wear of the current set of tyres must also be looked at. A simple renewal of tyres can likely mean the difference between an in-time emergency-stop and an expensive insurance claim and excess payment.

For instance, the longer a tyre has been in use, the harder the rubber would become. This would translate into less grip with the road, especially during braking. This is why a fresh set of tyres is grippier than an old set that still has lots of tread left.

So, when was the last time you took a good look at your rubber?

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