Rotor Compatibility Is About Parameters, Not Brands

from Rookie’s keyboard

Hello, friends

I wanted to share a principle that many people (not only in the bike industry) follow, namely – obsession with brands. 

A lot of people are too concerned with being “loyal” to a brand as if you’ve signed a contract with the manufacturer. The truth is that as long as the quality is right and the parameters are correct for your bike, then the brand is of lesser importance. 

For example, I’ve met (albeit only one time) fanboys of SRAM who would refuse to even use Shimano rotors for their brakes as if SRAM was their spouse or something. 

I am serious. A guy came into the bike shop of a friend and asked for rotors and we gave him Shimano rotors that fit his brake perfectly. He refused to take them due to “brand loyalty”.

I didn’t have the chance to share my opinion with him, but luckily, I have this blog and can do so with you. 

There is nothing wrong with using brake rotors made from a brand different from that of the brakes as long as the parameters of the new rotors fit certain criteria.

Requirements for Compatibility

Rotor Diameter

The diameter of the rotor should be compatible with your current disc brake setup. If the rotor is larger, you won’t be able to install the wheel at all, or the rotor will rub against the upper part of the caliper.

The diameter of the supported rotor depends on the mounts, the calipers, and the presence/absence of adapters.

If you want to install a larger rotor on a system designed to operate with a smaller one, you will need an adapter to increase the distance between the caliper mounting points on the frame/fork and the caliper itself.

Currently, there are three types of disc brake mounts – International Standard, Post Mount, and Flat Mount 

International Standard (IS) is the norm for older forks and frames. The brake caliper attaches via bolts screwing perpendicularly to the mount.

Modern fork manufacturers have completely abandoned the International Standard. 

Post Mount

Post Mount (PM) is found on modern bikes. The caliper attaches via bolts going straight into the mount.

If you have PMs designed to run 160mm rotors by default and want to upgrade to 180mm, you will need a 20mm post-mount adapter.  

Flat Mount(FM) is a fairly new disc mount standard found on road bikes. The caliper attaches to a flat part of the fork or frame. The goal is weight saving and simplicity. 

Currently, flat mounts are limited to 160mm rotors.

Conclusion 1: As long as the brake setup accepts the diameter of the new rotors, the combo should work well regardless of brand.

The Rotor and the Pads Should Be Compatible

Material wise brake pads separate into two groups:

  • Organic/Resin

Shimano’s organic pads are labeled as “Resin” whereas SRAM’s organic pads are referred to as just “organic”.

Organic pads are quieter and perform better in dry conditions.

  • Metal Sintered/Metal

SRAM calls their metal pads metal sintered whereas Shimano’s metal pads are referred to as just “metal”.

Metal pads are louder and offer better performance in rainy and muddy conditions.

Shimano’s lower-end rotors are softer and designed solely for resin/organic pads to slow down the wear.

Therefore, it’s not advisable to combine them with SRAM’s metal sintered pads.

Conclusion 2: The rotors should be compatible with the material of the pads.

Rotor Thickness

The thickness of the rotor is crucial for compatibility too. If the rotor is too thick, it may cause rubbing on brakes with new pads that don’t offer great clearance.

In the scenario discussed in the beginning, this shouldn’t be an issue because SRAM rotors are 1.85mm thick (source) whereas Shimano rotors have a thickness of 1.8mm (source). Since Shimano’s rotors are slimmer, they shouldn’t cause rubbing.

Having said that, you will still have to readjust the brake calipers upon switching to the new rotor system.

New or Used Rotors?

When converting to new pads with a different shape, it’s advisable to purchase new rotors too.

With time, the pads dig into the rotor and create a pattern. 

When you combine the same rotors with new pads shaped differently, the pads may press against a high spot on the rotor (an area that hasn’t been worn by the previous pads) and cause pulsation and excessive noise.

If you continue to use the old pads, you won’t experience that because the rotor’s shape wouldn’t be reaching outside of the “bed”.

Hub and Rotor Compatibility

Тhere are two types of rotors depending on how they attach to the hub – 6 or 7 bolt and center lock.

The bolt-on rotors attach via bolts going into threaded surfaces on the hub. This is the most common type.

The center lock hubs are a Shimano proprietary technology that secures the rotor to the hub via a lock ring similar to that of a cassette.

If you want to use a center lock Shimano rotor, you will need a center lock hub too. Otherwise, you won’t be able to install the rotor because you cannot convert a 6-bolt hub to accept center lock rotors.

If you have a center lock hub, however, you can install a 6-bolt rotor on it if you use an adapter.

Or in other words, center lock hubs give you the option of using both types of rotors whereas bolt-on hubs do not.

Until next time,






Leave a Reply

Your email address will not be published. Required fields are marked *