Have you read the FAQ? It's in the upper right-hand corner of the Brakes subforum.
What kind of fork do you have?
The BB5 brakes use what are known as a Post Mount (two posts with holes that are about three inches - 74mm - apart). If you have forks with Post Mount fittings you mount the brakes directly to them without an adapter and it will fit a 160mm rotor. For what you are trying to do you would need an adapter that spaces your brakes out to fit the 180mm brake rotor. It bolts between the brake caliper and the brake mount on the fork.
If your forks have IS mounts (two holes perpendicular to the wheel spaced about two inches apart (51mm) then you have an adapter already to convert your Post Mount brakes to IS mount because the BB5 brakes are Post Mount. Note that a Post Mount to IS 160mm front adapter will mount to the rear of the frame if the frame has the same IS mount but will fit a 140mm rotor. A front 180mm adapter fitted to the rear would fit a 160mm rotor, etc, etc. The rear IS mounts are 20mm lower than the front. For what you are trying to do you just need a 180mm front Post Mount to IS adapter. You swap out the adapters and rotors then you are pretty much done.
Hope this helps.
What kind of fork do you have?
The BB5 brakes use what are known as a Post Mount (two posts with holes that are about three inches - 74mm - apart). If you have forks with Post Mount fittings you mount the brakes directly to them without an adapter and it will fit a 160mm rotor. For what you are trying to do you would need an adapter that spaces your brakes out to fit the 180mm brake rotor. It bolts between the brake caliper and the brake mount on the fork.
If your forks have IS mounts (two holes perpendicular to the wheel spaced about two inches apart (51mm) then you have an adapter already to convert your Post Mount brakes to IS mount because the BB5 brakes are Post Mount. Note that a Post Mount to IS 160mm front adapter will mount to the rear of the frame if the frame has the same IS mount but will fit a 140mm rotor. A front 180mm adapter fitted to the rear would fit a 160mm rotor, etc, etc. The rear IS mounts are 20mm lower than the front. For what you are trying to do you just need a 180mm front Post Mount to IS adapter. You swap out the adapters and rotors then you are pretty much done.
Hope this helps.
