Brake adapters can be one of the more confusing parts that your bike needs in order to run larger brake rotors and disc brake calipers. Bicycles that have disc brake mounts are designed to work with a certain minimum rotor size on the front and back and if you want to use larger rotors or use a disc brake caliper that isn't supported by the frame you have then you'll need to use a disc brake adapter. There are several different ways that brakes mount to a bike.
Post-mount disc brakes mount directly into the frame or fork with two bolts that are 74mm apart. The posts and the threaded holes run parallel to the wheel. International standard, or IS disc brakes, are tabs that extend from the frame or fork with two holes that are threadless. These holes are perpendicular to the wheel, are 51mm apart, and require a special IS disc brake adapter. Flat mount disc brakes sit flush against the fork and on the rear of the frame. This standard of brake mounting is similar to post-mount disc brakes but use countersunk bolts.
There are many different disc brake adapters that go from post to IS, IS to post, post to post, IS to IS, and post to flat. Choosing the right disc brake adapter can be pretty easy once you know the type of mounts you have on your bike. If your bike naturally uses a 160mm rotor on the front and you want to use a 180mm rotor, then you need a +20mm adapter. If your bike uses a 180mm rotor and you want to use a 203mm rotor, then you need a +23mm adapter. Jenson USA is here to help those who need guidance when it comes to which brake adapters are required. Chat, email, or call our Gear Advisors at 951-234-7554.