Bicycle tires: Size, valves, systems...

What kind of bicycle tires are available? 
Bicycle tires and inner tubes come in different sizes, models, widths and with different tire profiles and rubber compounds. It is not so easy to keep track of them all.

The most important thing about bicycle tires is the diameter of the installed wheel in inches (or ETRTO specification in millimeters) and the width of the tire. The width of the tire can vary and be chosen flexibly. Basically, there are specifications from the manufacturer for the tire diameter and width. If you are not sure, you can simply use the old tire as a "sample" or orientation. 

Tire
If the tread is worn or the sidewall looks brittle, you should replace the tire to improve performance and avoid flats. The diameter (= installed wheel size) and the width of the tire are important. However, the tread of the respective tire and the air pressure driven are decisive.

Tire profile and tread
Mountain bike and cyclocross tires are available with different profiled treads while road bike tires for solid ground have almost no recognizable profile on the tread. A distinction is made between: 

• Tires with small, closely spaced lugs. These roll faster, but have less grip on loose and wet surfaces. They are ideal for fast and dry surfaces.
• Tires with large, often angular lugs spaced far apart. These often roll worse, but offer much more grip on soft surfaces. They are ideal for muddy terrain conditions.
• Tires with narrow tread in the center and prominent lugs on the edges (semi-slicks). These combine fast rolling characteristics on hard surfaces with some extra grip for cornering on loose surfaces.

Material
A tire's rubber compound - how hard or soft a tire is - affects its rolling characteristics, grip and durability. Harder rubber compounds tend to be inexpensive, roll well and last a long time. Softer rubber compounds are grippy but wear out faster. Some manufacturers therefore rely on a mixture of different hardnesses to appeal to a large group of cyclists. The following materials are common:  

• The classic among the tubes is made of butyl (butyl rubber). This is a very elastic and extremely airtight synthetic rubber. Due to its great elasticity, a butyl tube can be used for several different tire sizes.
• PU, or in this case thermoplastic, are extremely lightweight yet puncture and puncture resistant. On the negative side, however, tubes made of PU are quite expensive and only hold air for a short time. Thus, the tire pressure should be checked and adjusted before each ride. In addition, the tubes are almost inelastic, so only the appropriate size can be used with a certain tire size.
• Tubes made of latex are more elastic and puncture-resistant than their brothers made of butyl, but hold the air significantly worse.

Which tube systems are available? 
Not every tire is compatible with every rim. Basically, you have to ask yourself whether you want to ride your bike with or without a tube.

• Tubeless tires
  For a tubeless system, you need special thick-walled tubeless tires. Only these sit firmly on the rim even at low air pressure and can properly play out the advantages of the tubeless system. Because just the reduced air pressure is one of the main arguments for tubeless tires. Of course, these also roll easier due to the lower weight compared to tire-tube systems and the lack of friction between tube and tire. Last but not least, tubeless tires are also more puncture-proof, since the probability of a puncture is significantly lower and valve ruptures can not occur.
  Mountain bikers, cyclocrossers and also road cyclists appreciate tubeless for the plus in puncture protection, comfort and control. In addition, the rolling resistance decreases somewhat without the tube.
• Tubular tire
  With tubular tires, the tube is directly connected to the tire (sewn or vulcanized), which saves some material and thus weight.
  In case of punctures, you always come to a safe stop with tubular tires, because the tire, unlike tubeless, remains on the rim, even without air.
  Mainly they are used in racing on the road or in cyclocross competitions. This is because they roll very quickly and comfortably due to their design, cannot puncture and are very light.
• Clincher and folding tires
  Clincher and folding tires are traditional tires with a U-shaped cross-section and a reinforced tire bead, usually combined with a separate bicycle tube. Clincher tires have a steel reinforcement in the tire bead to sit securely on the rim. As a result, they cannot be folded and have a heavier weight.
  Folding tires instead used a lighter Kevlar core that makes the tires foldable. 
  Wire tires are slightly heavier and cheaper, folding tires save weight, but are also more expensive.

What types of rims are there? 
There are different types of rims:

• Clincher rims are the most common and widespread rims. However, this must be ridden with a tube. The advantage here is that in the event of a breakdown, the defect is extremely simple and quick to fix. In addition, it is quite inexpensive, since a tube is usually to patch.
• Systems without a tube (tubeless) are increasingly represented in the mountain sector and have become indispensable in professional sports. The omission of the tube increases puncture resistance, since air can escape only when the thick wall of the tire is punctured. Tubeless tires are always mounted with a few milliliters of special sealing milk, which foams up in a flash in the event of a sudden loss of air at the corresponding point and can thus close the hole. To ensure the protective effect, however, the milk should be replaced regularly. The appropriate interval varies from manufacturer to manufacturer and must be looked up in all cases. Another advantage of tubeless systems is the reduced weight due to the elimination of the tube.
• Tubular rims differ from clincher and tubeless rims primarily in the rim flange and rim bed. They do not have a classic rim flange, but are semicircular. This allows the tire to be bonded directly to the rim, which ensures an extremely secure fit. The tube is sewn (or vulcanized) directly to the tire in this system, which is why this can not be replaced separately.
   

Which valves are available?
At the latest when you have a flat tire, it is important to know which valve you have. There are three different types of valves:

• French valve, also: Sclaverand or Presta valve.
• Auto valve, also known as Schrader valve
• Bicycle valve, also: Dunlop or Blitz valve

The different valve types can be "transformed" by special adapters. This makes sense especially if you do not want to laboriously inflate your road bike or mountain bike, which is equipped with French valves, by hand, if you ever have a flat tire. With the help of an adapter from French valve to car valve, the compressor at the gas station becomes your helper. With regard to road bikes, however, it should be noted that these compressors can often only generate 5bar of pressure. So even as the owner of such a helper, you should not rely solely on the gas station.

Hoses with different length valves
Due to the widespread aero wheels with the high flanks, there are hoses with different valve lengths.

Valve caps
Valve caps have two functions. The first and seemingly obvious one: To protect the valve from dirt when installed. The second, occasionally underestimated: to protect the hose from the edges of the valve when it is carried as a spare when rolled up.
Therefore, the valve cap on the replacement hose is important to guarantee its tightness. On the installed hose, however, you can safely leave them out.

How to check the air pressure: Adjusting the air pressure 

You can find a selection of pumps here.