All You Need to Know Before Replacing Your Bike Tires.

Tire knowledge can be intricate, but I will tell all the essential information, including some surprising facts that may astonish even the most seasoned cyclists.

Since the introduction of the bicycle in 1817, there has been a continual demand for a tire to be placed on its wheel. The initial versions of these so-called tires consisted of metal bands that were fitted around wooden wheels. Unfortunately, these early tires provided minimal traction and were quite uncomfortable to ride on. It wasn't until 1887, when John Boy Dunlop invented the first pneumatic tire, that we were able to enjoy the comfort and convenience of air-filled tires. In case you missed this detail in your science class, "pneumatic" simply refers to the use of air.

Using a pneumatic tire instead of a solid one significantly reduces the rolling resistance of our bicycle tires, allowing the wheels to maintain their rotational speed. Additionally, aerodynamic drag is the largest force that slows us down when riding on a flat surface. Apart from these factors, bike tires have several other important functions. They must provide suspension and grip to ensure stability while balancing, turning, accelerating, and braking. When we talk about a tire's grip, we simply mean the friction between the tire's surface and the cycling surface. In addition to all these requirements, we also expect our tires to be lightweight, resistant to punctures, have low rolling resistance, and be cost-effective.

Given the multitude of elements to contemplate, it is evident why there exists a vast array of choices available. This is true even before taking into account variables such as wheel size, tire width, compound selection, tubeless or inner tube requirements, the option of tubular or hookless, and the specific surface for which it is intended.

A typical road bike tire consists of a casing composed of thin nylon or cotton fibers intertwined and covered with a thin layer of rubber. The central part of the tire, known as the tread, varies depending on the tire's intended use. On the sides, we find the tire bead. Older or more economical tires feature a non-folding solid wire bead, while most modern tires have a flexible folding bead. In the case of tubeless tires with folding beads, they need to be resistant to stretching and are therefore made from aramid or Kevlar fibers, similar to those used in bulletproof vests. This is quite impressive, but let's talk about different types of tire fitments and how tires are actually secured to the wheels. There are three main types: tubular, clincher, and tubeless. Traditionally, tubular tires have been favored for road racing. They consist of casings sewn around an inner tube, creating a complete tubular shape that needs to be glued to the wheel rim for proper clinching.

Bikes typically have tires that consist of a casing with a formed bead on each side. These beads interlock with the inner rim surface and are accompanied by a separate inner tube. Additionally, there are tubeless tires that closely resemble clincher tires. Tubeless tires have a meticulously designed tire bead that tightly interlocks with the inner wheel rim surface, creating a secure airtight seal. The casing of tubeless tires is slightly thicker than that of clincher tires and often utilizes a liquid sealant to enhance puncture protection and maintain air pressure for extended durations.

The tire width refers to the measurement of how wide the tire is in millimeters once it is installed on a wheel inflated to the correct pressure. It is important to note that the actual measured width of the tire may differ from what is stated on the box or side wall, as it is influenced by the internal width of the wheel rim. The width of the tire is directly affected by the width of the inner rim, meaning that a wider inner rim will result in a wider tire. With the wide variety of tires and rim widths available, and considering that modern wheels are becoming wider, it is crucial to ensure compatibility between the tires and rims you purchase. It is recommended to thoroughly research and read about your next purchase to avoid any potential issues.

Road tires for casual and racing cyclists typically range from 23 to 32 millimeters, while tires suitable for road and gravel bikes range from 33 to 50 millimeters. In simpler terms, wider tires offer more comfort than narrower ones, but tire pressure should be considered in relation to tire width. In the bike industry, tire pressure is measured in PSI (pounds per square inch) or bar. One bar is equal to 14.5 PSI, and one PSI is equal to 0.7 bar or 0.0689476 for those who prefer precision. Floor pumps and some mini pumps have gauges that display these units, usually indicating the maximum pressure. However, this maximum pressure should not be used as a recommended pressure for everyday use. The optimal pressure depends on factors such as tire width, system weight (including the rider, bike, and gear), tire type, and riding surface. Fortunately, there are numerous helpful guides available from manufacturers to provide a starting point for tire pressure. The general principles to follow are: the wider the tire, the lower the pressure; the heavier the rider, the higher the pressure; for bumpy surfaces, lower the pressure; and for slippery surfaces, lower the pressure.

In the past, we used to call our tires 700c, but that designation is no longer accurate. Originally, the "700" referred to the outer diameter of the tire, while the "C" indicated the width. We even had variations like 700a, 700b, 700c, and 700d to provide different options. However, this system had a drawback. As the tires became wider and larger in volume, we needed to use different-sized wheels to maintain the same outer diameter of 700. Looking back, it seems a bit crazy now. Today, what we call 700c tires adhere to the ISO standard 5775, which means the tires have a bead measurement of 622 millimeters in diameter. The actual outer diameter will vary slightly based on the tire width when inflated. If you examine your tires, you'll find this information stamped on the side. There's also a smaller tire size called 650b, which is fitted on certain extra small road bikes or gravel bikes. The bead measurement for 650b tires is 584 millimeters. Additionally, urban or commuting bikes may use even smaller 26-inch steel tires. I apologize for introducing yet another measurement and number into the equation, but that's simply how the bike industry operates!

The tire casing serves several important functions, including strength, flexibility and resistance to punctures. Its construction is measured in TPI (threads per inch), which refers to the number of threads that cross through a square inch of a single ply of tire casing. A lower TPI count offers better puncture resistance but adds weight due to the increased use of rubber. On the other hand, a higher TPI count provides a more supple casing, resulting in a smoother and more comfortable ride while reducing the tire's weight. In addition to the TPI, tire casings often have a puncture protection belt layer positioned just below the tread, which is the thicker central part of the tire. This tread can feature a variety of patterns, ranging from completely slick to subtle or more defined, such as those found on gravel or urban road tires. The tread plays a crucial role in providing grip, with a more pronounced pattern offering increased traction on loose or muddy surfaces. However, this increased grip comes at the expense of speed on regular roads. The tire's compound materials primarily determine its grip, which is why tire manufacturers closely guard their rubber compound secrets. A harder and less flexible compound resists wear and punctures but sacrifices grip, while a softer compound provides maximum grip but wears out quickly and is more prone to damage. Achieving the perfect balance is challenging and depends on factors such as the tire's intended application and the temperature conditions it will encounter. For example, winter tires use a compound that remains supple in the cold, while summer tires have a firmer compound that provides reduced grip in low temperatures.