The bicycle in Pokémon Sword and Shield is slow. Sometimes, it even feels like you can running faster than the speed that the Rotom Bike provides.
Fortunately, there’s a way to upgrade its speed, as long as you know where to look.
Located around various parts of the Wild Area, mostly near entrances to towns or next to the Day Care Center, you can find a man in white. You can ask him to speed up the Rotom Bike in return for Watts.
It’ll take a sizeable amount of Watts to increase the speed of the bicycle, but it’s definitely worth doing if you plan to ride around frequently.
You can also increase your base speed when riding around on the Rotom Bike by pressing the B button to get a temporary burst of speed. This is a decent alternative if you don’t want to invest Watts into the bike yet.