Road bikes use Presta valves for the following reasons:
1. Thin rims
For aerodynamic and weight-saving purposes, road bikes have thin/narrow rims designed for slim tires.
The outer diameter of Presta valves is 6mm (0.24in) whereas that of Dunlop and Schrader valves is 8 mm (0.31 in). This property makes Presta valves the thinnest.
The valve hole (the entry on the rim through which the valve passes) requires the removal of material and consequently weakens the rim. The bigger the hole, the weaker the area becomes.
The narrowness of Presta valves makes it possible to use a thin rim that is still sufficiently strong for a road bike. If a Schrader valve is drilled on the same rim, the valve area will be notably weaker, and the rim may give up at one point.
Note: This property was a bigger advantage in the past when road bikes were using maximally narrow rims. Currently, the industry is relying on wider rims negating the advantage of small valve holes.
2. Supreme Air Pressure Control Mechanism
The mechanism of a Presta valve has key advantages.
The regulation of air intake happens via a unit known as a valve core. When the valve core is unscrewed and pressed down, the valve opens.
When the user stops pressing the valve core, the valve closes and terminates the deflation of the tire. From the outside, it looks as if there’s a spring that pushes the valve core to its original position, but there isn’t one.
The air inside the inner tube pushes the valve core back. If the inner tube is empty, the valve core will not return to its starting position.
This property gives the following advantages:
- No air loss when removing the pump
A healthy Presta valve does not permit the loss of air upon removing the pump’s chuck because the air pressure pushes the underside of the valve core and seals the entire valve. Of course, the user still has to tighten the valve core so that it doesn’t open during riding.
This feature is key for road bikes because road tires are small and pumped to very high air pressures. If there’s even a small leak, the air pressure will be greatly affected because each unit of air represents a higher percentage of the total volume inside the tire.
- Less Air Loss
Regardless of the valve, a tire will lose air over time. That said, Presta valves are known for maintaining high air pressure longer than other valves.
- Compatible With Extensions
Deep dish rims aren’t compatible with standard Presta valves due to their size and require an extension that treads onto the original valve. The extension elongates the valve and makes it compatible with deep dish rims. Such extensions aren’t available for Schrader valves.
Presta valves are 4-5grams lighter than Schrader. Thus, a bike can save 10 grams by using Presta valves. It goes without saying that 10 grams are of absolutely no importance unless one is trying to build the world’s lightest bicycle.
- Easier To Pump
The absence of a spring makes Presta valves easier to pump with a hand pump.
Presta valves have been the norm for a long time. Given that the other valves have no game-changing advantages, most cyclists see no reason to replace a classic.
The strongest downside of Presta valves is that you can’t pump them without a bike-specific pump. However, that problem can easily be fixed by using a Presta to Schrader adapter.
Some riders keep such an adapter permanently attached to their Presta valves.
By using the adapter, you are essentially getting the best of both worlds.
- Dissociation with Other Bicycles
The vast majority of bikes (MTBs, hybrid, city…etc.) use wider tires with Schrader or Dunlop valves. Road bikes are meant to be different. A unique valve designed specifically for bicycles like Presta compliments this goal.
It’s subjective, but many road cyclists consider Presta valves more aesthetically pleasing.
- The European Connection
The Presta valve was invented by Frenchman Etienne Sclaverand and is referred to as the French valve. Since in the past most road bikes were imported from Europe, they came with Presta valves by default.
FAQ: What are the downsides of Presta valves?
- Less popular
Presta valves are strictly designed for bicycles and are therefore absent on other vehicles. Consequently, the vast majority of pumps out there are not compatible with a Presta valve. The same applies to gas station compressors. As already mentioned, an adapter circumvents this issue.
The length, thinness and construction of Presta valves make them more susceptible to external damage. That said, Presta valves are still plenty strong for a road bike.
- Extra Steps
To inflate a tube with a Presta valve the user has to unscrew the valve core and then tighten it again. Those are two extra steps that the Schrader valve does not require.
FAQ: Is it true that Schrader valves cannot cope with the air pressure maintained by Presta?
Not really. Schrader valves can maintain just as high air pressures as Presta. All air shocks, for example, use Schrader valves and are capable of maintaining 120+PSI.