We’re focusing on rotors and pads because upgrading the entire braking system may not be necessary to get you the power you need. Especially on more affordable bikes, brands often choose pad and rotor spec that will get the job done for most riders, but maybe not for you. We’ll break down a little about the difference between the variety of pads and rotors you have to choose from, and what you need to keep in mind when you’re ready to hop up your stoppers.
Bicycle disc brake pads are divided into two categories. There are ‘organic,’ also known as resin, and there are ‘metallic,’ also known as sintered. Organic pads are usually a mixture of fibrous particles bonded together by a resin glue, while metallic pads are made of metallic particles that are compressed and bonded together with heat. On the trail, organic pads tend to be a bit quieter, but they are less effective in the wet and will lose power as they heat up under prolonged braking. Metallic pads work great in the wet, and do well when subjected to prolonged heat buildup, but they are more likely to be noisy, though that’s rarely severe enough to overshadow their benefits. They also are harsher on rotors over time, and some lower-priced bikes come with rotors that can not be used with metallic pads.
Though this is not always the case, lower-priced bikes tend to come stock with organic pads. The dry, cool-temperature, moderate-speed performance of metallic and organic pads is very similar, but organic pads tend to give the brake a slightly softer feel at the lever. If that bothers you, or if your descents are prolonged and steep, swapping to metallic pads is an inexpensive way to improve your brake performance as long as your rotors are compatible. If the rotors are not compatible, they will almost always be laser-etched somewhere indicating they are for “resin pads only.”
Identifying the pad material is sometimes more difficult. Most brands will identify a pad’s material by stamping it in the metal backplate, but not always. There is no reliable way to go by color or texture to identify metallic or organic pads. Metallic pads may have some shiny or reflective particles, but if an organic pad has been used, there may be specks of material smooth enough to reflect light like metal. Some organic pads use an aluminum backplate, which you can identify easily because it is not magnetic. Some metallic pads use titanium backplates which also are not magnetic, but this is extremely rare.
If you have no visual clues which pads you have, go by your experience. If your brakes tend to lose power, or ‘fade,’ on long descents, it is possible that they are organic, and a $20 to $30 (per wheel) trip to the bike shop is a good place to start. In the case of some entry-level Shimano brakes or on brands like Tektro or Promax, the brake manufacturer may not make metallic pads for your particular brake, but there are third-party manufacturers like EBC, Clarks, Galfer or Jagwire who likely make metallic options for your pad. Just make sure you follow their guide for picking the right pad because many look similar.
If heat buildup is indeed the problem you’re facing, Shimano has introduced the pads you’re seeing in these photos, with aluminum heat sinks that dissipate heat into the air with an increase in surface area. All but the most entry-level Shimano brakes can be fitted with on-brand heat sink pads. Aftermarket brands like Kool Stop and Swisstop may make a heat-sink pad for your brakes if you are finding a drastic loss of power after your brakes have built up extreme heat on a prolonged descent. Just keep in mind that heat sink, or ‘finned’ pads tend to rattle in their calipers, enough to be a deal-breaker for some riders.
Whenever working with rotors and pads, be sure to keep them away from oil and wax, as the pads are porous and can get ruined if they are contaminated. Always wipe off the rotor with alcohol and a clean rag after handling it.
If you are swapping rotors in order to change to metallic pads, it’s simple to tell if it’s necessary on major brands Shimano and SRAM (possibly branded as Avid, depending on your bike’s age). Shimano rotors will always indicate if they are resin-pads only, and SRAM does not make resin-only rotors. It is not as simple on other brands of brakes. If it is not written on the rotor, you may be able to tell by looking closely at the rotor itself. Less expensive resin-only rotors are usually manufactured by being stamped, not machined, and you can tell by looking closely at the edges of the rotor material. If they are sharp, square edges, it is likely a higher-quality rotor and you’re free to use the pad of your choice. If they are slightly rounded or chamfered, you may have a resin-only rotor.
But that is definitely not the only reason you might want to change rotors. The easiest and cheapest way to increase the power in your braking is to swap to a larger-diameter rotor. The three most popular diameters are 160, 180 and either 200 or 203 millimeters (some brands use 200, some use 203, and no, that doesn’t really make sense but we’ve gotten used to it).
There are a few 140-millimeter rotors in the lightweight cross-country and gravel market, and a growing number of 220-millimeter rotors in the downhill and enduro market. A larger rotor gives the brake caliper more leverage against the wheel, simply offering more power. It also provides more surface area to distribute the heat buildup, leading to less fade. But larger rotors are heavier, and are easier to slightly bend if they come in contact with objects on the trail or if the bike is not carefully transported, though most riders with large rotors consider it worth the risk.
Before increasing the size of your rotor, keep in mind that some frames and forks have a maximum rotor size. If it is not indicated on the component itself, it is safest to check with the manufacturer.
Your rotor size will be stamped somewhere on the rotor itself. Most bikes, just like most cars, will run a larger rotor in the front where there is the most potential braking power and a smaller rotor in the rear where too much may just send you skidding. If you are finding yourself putting enough force into your brake levers that your hands and forearms are becoming fatigued, but you are still not slowing down quickly or consistently enough, or if you are experiencing brake fade despite running metallic pads, it is probably time to go to larger-diameter rotors.
There are two ways that rotors can be attached to the wheel. The vast majority use six small bolts, but Shimano introduced a system called Centerlock, using one large hollow ‘bolt’ concentric with the axle. This requires a special tool to change. If that large hollow bolt is notched on its inner surface, you need what is often called a ‘cassette lockring tool.’ If it is notched on the outside, you will need a 16-notch 44mm bottom bracket tool. If you have Shimano brakes, it may be equipped with either system, but nearly every other brake brand will be six-bolt, which requires only a T25 Torx wrench, and it is likely on the tool you already take on the trail.
Once you’ve gotten the right rotor interface, and you know your frame or fork can handle it, all you need is the correct caliper adapter to position the brake itself out on the larger diameter rotor. For several years, there has been one standard on forks and frames called ‘post mount.’ These threaded ports will usually default to a 160mm rotor, meaning the brake caliper will bolt on directly with no adaptor if you are using a 160mm rotor. On more aggressive, gravity-oriented frames and forks, they may default to a 180mm rotor.
Finding the adaptor you need is simple arithmetic. If you have a 160mm post mount and you want to install a 200 or 203mm rotor, you need a 40 or 43mm post-mount adaptor and the accompanying bolts, which will come packaged with the adapter. If you have a 180mm post mount, you will be looking for a 20 or 23mm adapter.
Again, the brakes themselves can be upgraded, but that can quickly become a several-hundred-dollar job, whereas a larger rotor and adapter may only cost $50 per wheel, and different brake pads may be even less. And the best part is, these swaps only require simple tools and minimal experience in wrenching on your bike.