Grinding (グラインド Guraindo?) is the act of balancing on a rail or some rail-like object. Grinding is a big mechanic in the Sonic series. By doing this, characters can gain speed/momentum while on the rail. Grinding first appeared in Sonic Adventure 2 but can only be used by Speed Type characters such as Sonic or Shadow. Also, those characters only wear Soap shoes in order to grind. Grinding is required to defeat the Biolizard.
In later games, such as Sonic Heroes, Power Type and Flight Type characters can also grind. In addition, the characters don't need to wear Soap Shoes in order to grind. Also, games before Shadow the Hedgehog required the use of balancing on the rail via control stick in order to properly maintain speed. This was removed possibly due to need for simplicity and possibly the fact that Sonic and his friends grew more experienced (along with the fact as of Shadow the Hedgehog, rails have somewhat expanded in size and are less thin).In Sonic Riders and its sequel, only Speed type Extreme Gears (Skates or Board with Grind gear part) can grind on rails when it reaches a certain level. In Sonic Free Riders, the grinding gear alone can be set for gears (except for the Beginner as it cannot have any gear parts) including Bikes.
In Sonic Heroes, Shadow the Hedgehog, and Sonic 06, if the player presses the X button (Xbox/360), the B button (Gamecube), or the square button (PS2/PS3) the character will do a little spinning 180 hop on the rail which will make them go a bit faster. This no longer happens as the Boost can be used to go faster when grinding in the newer games. Although the flip can still be done for no effect in Sonic Unleashed, Colors and Generations by pressing either the B button (Xbox 360) or the circle button (PS3).
Grinding once again appears in all versions of Sonic Generations. However, it not only appears in stages that originally had rails, it appears in some stages without it in the past, such as Mushroom Hill.
- According to Sega, the grinding mechanic's addition to the Sonic series was heavily inspired by the fact that they were working on Jet Set Radio, which originally used the mechanic, around the same time Sonic Adventure 2 was in development.
- Classic Sonic doesn't "grind" in Generations, more he just rolls along the rail. Bizarrely (and somewhat painfully), this still causes sparks and metallic scraping. This is more noticeable in Crisis City and City Escape.