Differences between Post-mount And IS mount On A Bike

 What is Post-mount and IS mount

Post-mount:

• Post-mount is a disc brake mounting standard that involves attaching the brake caliper directly to threaded posts on the bike frame or fork, bolts spaced at 74mm.
• The mounting posts are positioned parallel to the rotor and are usually found on the fork or frame. They may be positioned at different distances apart, depending on the specific design.

IS mount (International Standard mount):

• IS mount is another disc brake mounting standard that uses a set of two mounting tabs spaced at 51mm (International Standard) apart.
• In the case of disc brakes, IS mount is commonly found on the fork, and the brake caliper is attached to these tabs using bolts.
• The caliper is then aligned with the rotor, which is mounted to the wheel hub.

In general, the choice between post-mount and IS mount often depends on the specific design of the bike frame or fork, as well as the type of disc brake system being used. It's important to use the correct adapter or mount type for your specific components to ensure proper alignment and performance. Manufacturers will typically specify the type of mount their frames or forks support, and brake calipers may come with adapters to accommodate different mount standards.

 Advantages and Disadvantages between Post-mount and IS mount

Both post-mount and IS mount systems are widely used in the cycling industry, and each has its own set of advantages and disadvantages. Here's a brief overview:

Advantages of Post-Mount:

1. Simplicity and Integration: Post-mount systems often allow for a more streamlined and integrated look. The brake caliper can be directly mounted to the frame or fork without the need for additional adapters in many cases.

2. Frame/Fork Compatibility: Some bike frames and forks are designed with specific post-mount dimensions, and using a post-mount brake caliper can simplify compatibility.

3. Lighter Weight: In some instances, post-mount systems may be lighter due to the more direct connection between the brake caliper and the frame or fork.

Disadvantages of Post-Mount:

1. Limited Adjustment: Post-mount systems may offer less adjustability compared to IS mount. The fixed position of the posts might limit the range of adjustment for caliper placement.

2. Frame/Fork-Specific: Frames and forks with post-mounts may not be as versatile when it comes to accommodating different rotor sizes without the use of adapters.

Advantages of IS Mount:

1. Adjustability: IS mount systems typically provide more adjustability, allowing for easier alignment of the brake caliper with the rotor. This can be particularly useful when using different rotor sizes.

2. Versatility: IS mount systems are often more versatile, allowing the use of adapters to fit different rotor sizes and types.

3. Widespread Standard: The IS mount standard has been widely adopted in the industry, making it easier to find compatible components.

Disadvantages of IS Mount:

1. Bulkier Appearance: IS mount systems, especially when using adapters, can sometimes appear bulkier and less integrated than post-mount systems.

2. Additional Adapters: Depending on the specific frame, fork, and rotor size, you may need additional adapters to fit the IS mount system properly.

In summary, the choice between post-mount and IS mount often comes down to factors such as frame/fork compatibility, aesthetic preferences, and the desired level of adjustability. Many modern bikes and components are designed to work seamlessly with either system, and the performance difference between the two is often minimal when properly set up.