A Shimano Hollowtech bottom bracket may have a shell made of metal or tough plastic.
Shinamo Hollowtech bottom brackets need a special ring spanner that fits into splines and allows each side to be screwed in and out.
Acces the bottom bracket
Remove the cranks
Push the ring spanner onto the external splines on the left side of the Shimano Hollowtech bottom bracket. Hold it in place with one hand while you apply torque with the other
Loosen The Left
Start the left-hand cup moving anti-clockwise
Loosen And Remove The Right Side of theBottom Bracket
Move the ring spanner to the right side of the Shimano Hollowtech bottom bracket and start it moving clockwise. Keep going until the unit comes out.
Return To The Left
Move back to the left side and unscrew the rest of the unit. You may or may not need to use the ring spanner for this.