The first thing we notice is how much steeper and more aggressive the initial application of the braking force is with the new tires. The old ones must be loaded more gradually, as shown by the rounder and shallower initial part of the speed curve. Those first few miles per hour needed to come off slowly while we found the ideal pedal pressure to avoid terminal lockup.

We also see the main part of the speed trace for the Yokohamas dropping more steeply than the Pirelli trace. This shows us losing speed at a faster rate with the newer tires.

At around 35 mph, we see the Pirelli trace flatten out completely for a moment as the right-front tire locked up, forcing us to get out of the brakes and then back in to continue the braking exercise.

Conversely, while the Yokohama trace has many tiny changes in deceleration rate due to threshold braking, we never see a point on the curve where the car stops decelerating at an aggressive rate.

Toward the bottom of the curve, we were doing some serious modulation with the old tires to keep them from terminal lockup. That’s the sawtooth part of the trace toward the bottom.

Except for one small hiccup at the bottom of the Yokohama trace, which was not a lockup but more likely just road undulation, the Yokohama curve just continues downward to a stop.

Even the stops themselves are different. The Yokohamas came to a full and complete stop in one motion, while we had to “chauffeur stop” the old tires at the last second by bleeding off some braking force to keep them from sliding to a stop.

And while we’ve offset these curves from each other slightly for reading clarification, we can still see a distance advantage in the newer tires. The Yokohamas came to a full stop almost 10 meters shorter than the old tires. And while the distance is great–you can fit a lot of kids on bikes in 10 meters, nearly 33 feet–the even bigger story is the lack of drama the new tires displayed while they did their job.

5 Tips for Proper Tire Storage

While tires naturally age over time, a few environmental factors can accelerate the aging process. Keep yours away from:

• UV light and radiant heat
• Excess humidity
• Wide temperature swings
• Underinflation and overinflation
• Ozone-producing electric motors

So, How Old Are Those Old Tires?

A tire’s age is revealed in its Tire Identification Number–more of a batch code than a true serial number. From the Tire Rack website: “Since 2000, the week and year the tire was produced has been provided by the last four digits of the Tire Identification Number, with the 2 digits being used to identify the week immediately preceding the 2 digits used to identify the year.”

What about tires built before 2000? They follow a different system, but they’re all well past their expiration date.



The Tire Identification Number reveals all: This tire was built during the 40th week of 2016.