The bike industry is an ever changing beast. Evolving technologies are always redirecting the state of bicycle performance and aesthetic. Sometimes this is a real benefit, like threadless headsets, but some things don’t hold up over time. Remember Octalink bottom brackets or U-brakes?

A more detailed article explaining the differences between flat mount and post mount can be read here

One newer piece of equipment causing some confusion is the flat mount disc brake caliper. Developed by Shimano and introduced in 2015, the flat mount caliper is supposed to be simpler and sleeker than the post mount caliper that became standard on mountain bikes. Intended for road bikes, the flat mount caliper sits directly on the chainstay or fork blade, taking up less space than a common post mount caliper. For aesthetic minimalists, mounting the brake inside the rear triangle is better looking. What are the mechanical benefits, if any?

Modern disc brakes started out using IS (International Standard) mounts, often called “disc tabs”. These have two threadless holes running parallel to the hub axle that are used to mount an IS caliper or an adapter for a post mount caliper. The lack of threads meant users were less likely to damage their frames accidentally during maintenance or installation. Post mount calipers are often adapted to IS mounts because the variety of adapters allows for tremendous flexibility in rotor size. A post mount caliper affixed to an IS mount can use any rotor size between 140mm to 203mm, depending on the adapter used.

Flat mount calipers are designed to look cleaner. There are only two small adapters and flat mount calipers are limited to 140mm and 160mm rotors. This is reasonable since these are the standard sizes used on road bikes. Adapter plates are small and sandwiched between the caliper and the frame, saving space. There are weight savings, but they are somewhat negated by the frame and fork being beefed up to provide mounting points and withstand the braking forces incurred.

You can see these two approaches to disc brakes here at Rodriguez Bicycles. Our Phinney Ridge uses post mount calipers adapted to IS mounts for the greatest range of flexibility. Our Bandito disc road bikes have a focus on road performance and light weight and we use a flat mount caliper in the rear triangle. The Bandito often uses a post mount front brake due to limitations in fork design availability. We prefer a straight 1⅛”  headtube because of the significant weight saving it offers. However, this currently limits us to carbon forks that use post mount calipers. This is one area where we feel the weight savings is worth it.

Disc brakes have become a dominant force in modern cycling. They have opened up frames to ever wider tires and brought hydraulic braking to more riders. For those of us that ride year round in the Pacific Northwest, they have given us a reprieve from excessive rim wear caused by the wet grit that coats our wheels in the winter. While not perfect for every application, they are a technology that has proven itself a valuable option for many riders. If you’re interested in a bike with disc brakes, we’d be happy to discuss which options are right for your cycling goals.

To see more examples of Rodriguez disc brake bikes, check out the Phinney Ridge and the Bandito. The Makeshift is also available with disc brakes.

Here’s an older article about the history of disc brakes in the cycling industry from 2012.