The Hollowtech II bottom brackets provide the best balance of stiffness, strength, weight
and rotating performance
What size do I need?
Measure the inner diameter and most importantly, the width of your frame's bottom bracket shell
Assuming you have a BSA threaded bottom bracket shell, the width varies from 68 to 100 mm
Road bikes and hybrid bikes share the same shell width, they are all 68 mm
Mountain bikes' bottom bracket shells are 73 mm
Downhill bikes are 83 mm and fat bikes are 100 mm
The Hollowtech bottom bracket comes with spacers to fit 68 and 73 mm bottom bracket shells
There's a 2.5 mm gap on the drive side to install a chain guide
or a derailleur with bottom bucket mount
These are optional and you could use a spacer to fill the gap
Install the spacer on the drive side
Starting from the drive side, turn it counterclockwise and use the tool to tighten it
On the non-drive side, turn it clockwise