Condensed answer: Shimano rotors can be combined with SRAM brakes. In some cases, you will need an adapter or an extra washer to increase clearance.
Requirements for Compatibility
1. Rotor Diameter
The diameter of the rotor should be compatible with your current disc brake set-up. 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.
Note: Modern fork manufacturers have completely abandoned the International Standard.
If you have IS mounts and want to switch from 160mm to 180mm rotors, you will need a +20 IS to Post Mount adapter.
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 set-up accepts the diameter of the new rotors, the combo should work sufficiently well.
2. The Rotor and the Pads Should Be Compatible
Material wise brake pads separate into two groups:
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 pads 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.
What About Rotor Thickness?
The thickness of the rotor is also important for compatibility. If the rotor is too thick, it may cause rubbing on brakes with new pads that don’t offer great clearance.
In the discussed scenario, 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
When buying a new rotor, you should also make sure that it’s compatible with your hub.
Currently, there 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 drilled and threaded surfaces on the hub. This is the most common type of rotors.
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 options of using both types of rotors whereas bolt-on hubs do not.
Summary: What You Need To Know
You can use Shimano rotors with SRAM brakes when:
- The current brake system is compatible with the diameter of the new rotor. If you’re switching to a larger rotor, you will need an adapter. If you’re running Shimano 203mm rotors, you may also need an extra washer for additional clearance.
- The new rotors should be designed to operate with the material that the brake pads are made of. If the rotors are engineered solely for organic/resin pads, but you want to run them with metal sintered pads, you will need another set.
Shimano rotors are thinner (1.8mm) and will require readjustment of the calipers to prevent rubbing and optimize the biting of the brakes.
It’s recommended to buy new rotors. If rely on old ones, the new pads may be biting the rotor unevenly and causing unpleasant vibrations and noises.
The hub and the rotor should be compatible. If the hub has a bolt-on mounting system for the rotor, you will be limited to bolt-on rotors.
If the hub has a center lock system, you can use standard center lock rotors or 6-bolts rotors (you will need an adaptor for those).