Condensed Answer: Hope brakes can be combined with SRAM rotors when the following criteria are met:
1. The diameter of the rotors should be compatible with the brake calipers.
2. The rotors shouldn’t be too thick or thin for the brakes.
3. The brake track of the rotors shouldn’t be too narrow.
4. The mounting system of the rotor should match the one on the wheel’s hub.
That said, the expected performance of Hope brakes is guaranteed only when the brakes are coupled with the rotors specifically designed for them.
Hope rotors come in the following sizes: 140, 160, 180, 183, 185, 200, 203, 205, 220, and 225mm.
Meanwhile, SRAM offers the following diameters: 140, 160, 170, 180, 200, 203, and 220mm.
The size overlap greatly increases the chances to find a rotor of a compatible diameter.
FAQ: Can I use a larger rotor than the original one?
If the new rotor is larger than the original one, the user will be unable to install the wheel due to the lack of room for the rotor or the rotor will rub against the caliper.
That said, it’s possible to upgrade to a larger rotor by installing a disc brake adapter.
Disc brake adapters act as spacers and increase the distance between the caliper and the brake mounts. As a result, the user can install a rotor of a larger diameter.
FAQ: Can I use a smaller rotor than the original one?
If the rotor is smaller than originally intended, it will not create fitting issues. However, a smaller rotor than what the bike was originally designed for can result in a phenomenon known as brake pad overhang.
Brake Pad Overhang Explained
The part of the disc rotor that the brake pads grab is known as brake track.
When the rotor is smaller than originally intended, a section of the pads never comes in contact with the rotor.
Consequently, that section never gets smaller because there’s no friction between it and the rotor. The rest of the pads, however, gets smaller with time.
Eventually, the parts of the pads that never come in contact with the rotor touch each other and prevent the brakes from closing further.
As a result, the brake fails to close sufficiently to grab the rotor and slow down the wheel.
Thus, brake pad overhang makes a brake useless over time.
The other two sources of brake pad overhang besides using smaller rotors are:
- Excessively large disc brake adapters
- Brake rotors with extremely narrow brake tracks.
The measures necessary to avoid brake track overhang are:
1. Don’t use smaller rotors than what the brakes are designed for.
2. Make sure that the brake adapters are not larger than necessary.
3. Measure the brake tracks of the original rotors and compare them to the new ones.
The thickness of the rotor is the next important parameter. Ideally, the new rotors will have the same thickness as the ones that are being replaced.
The thickness of a rotor directly influences the modulation of the brakes.
Brake modulation is a term describing the control that the rider has over the braking force.
If the rotor is thicker than necessary, it will be extremely close to the brake pads.
When the rider squeezes the lever, maximum braking power will be reached very quickly. It will feel as if the brakes are working in on/off mode. The lack of sensitivity degrades the braking experience.
If the rotor is too thin, the brake pads have to move more to grab it. As a result, reaching maximum braking force takes additional time and brake lever travel. In that case, the extra modulation hurts the performance of the brakes.
The standard thickness of most rotors is 1.8-1.85mm. Most SRAM and Hope rotors fall within that thickness range and are therefore interchangeable in that regard.
However, the companies have thicker rotors too. For example, Hope has a Heavy Duty 2.3mm rotor whereas SRAM has 2mm rotors.
Replacing a rotor of that thickness with slim 1.85mm models will quickly result in degraded performance due to the extra brake pad travel. It will feel as if the brake pads are worn even when they aren’t.
Thus, for best performance, it’s recommended to stick with SRAM rotors as close as possible to the thickness of the original Hope ones.
Hub Attachment Mechanism
The mounting system of the new rotors is important too. A rotor may be compatible with a set of calipers but that wouldn’t matter if you can’t mount on the wheel’s hub.
There are two main options – center lock and 6-bolt.
Center lock hubs rely on a Shimano patented technology. The rotor is mounted and secured to the hub via a lock ring similar to that of a cassette.
If you have bolt-on hubs, you will need a bolt-on rotor.
If you have a center lock hub, you have two options:
- Install center lock rotors
- Install bolt-on rotors by using an adaptor
Summary: What You Need To Know
SRAM rotors will operate properly with Hope brakes when the following criteria are met:
- The diameter of the rotors should match the one supported by the brakes. If a bigger rotor is needed, the user can install an adapter.
- The thickness of the rotors should also be compatible with the brakes. Thin rotors result in extra modulation. Thick rotors decrease modulation.
- The brake tracks of the rotors should be of similar size or else brake pad overhang will render the brakes useless over time.
- The mounting system of the rotors should be compatible with the hubs on the wheels.
The optimal performance of Hope brakes is guaranteed only when the brakes are used with the original rotors designed for them. That said, people have successfully used rotors from other brands including SRAM and Shimano.
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There’s certainly a great deal to know about this topic. I love all the points you’ve made.