Posted in Cycle
SRAM Guide RS Disc Brake

What are disc brakes?

Disc brakes are a powerful and progressive braking mechanism; a hydraulic or cable actuated caliper forces the disc brake pads onto a rotor to slow down or stop your bike.

The vast majority of disc brakes on mountain bikes are hydraulically activated; brake fluid drives pressure to the caliper and this results in a clamping force on your rotor via the brake pads. The physical act of braking is caused by the friction generated by the brake pads and the rotors. Hydraulic disc brakes are lighter, more reliable, feel better and are more powerful than cable actuated disc brakes. Cable discs however are cheaper and if you already have a bike with cable rim brakes, you don’t need to buy new brake levers as a cable disc brake will use conventional-style cable pull brakes.

Do all mountain bikes use disc brakes?

Not all mountain bikes use disc brake platforms - however most modern full suspension and hardtail bikes will use a hydraulically activated disc brake system. Disc brake technology has evolved to a point where the technology has trickled down to much more competitive price points and as a result it’s common to see disc brakes used on mid to entry-level bikes. Another reason is frame design; modern day mountain bike frames built for off road performance will be constructed with disc brake mounts instead of cantilever mounts.

Can I retrofit disc brakes to my mountain bike?

Disc brakes can be fitted to any mountain bike so long as the bike is equipped with two things:

  • Hubs that have the fittings for a disc rotor.
  • Frame and forks which have mountings for disc calipers.  

Shimano XT M785 Disc Brake Lever and PM Caliper

What are the benefits of using disc brakes?

  • Power: Disc brakes are significantly more powerful than cantilever or V brakes.
  • Control: Progressive braking allows you to benefit from powerful braking performance without any compromises in control when riding your bike.
  • Confidence: The combination of power, progression and versatility in all weather conditions can translate into more confidence on the trail. The ability to brake with confidence also means that you will be safer and more able to tackle any technical challenges when they arise.
  • Versatility: Disc brakes also provide reliable performance in all weather conditions; this sets them apart from any rim brake design which can suffer from rim wear and inconsistent performance in the wet.

Disc brake mounting systems

When you find the disc brake of your choice and wish to make a purchase it's essential that you ensure the brake has the correct mounting system for your frame and fork. The measurement of disc brake mounts is based on the distance in millimeters between the the center of the two bolt mounting holes. If your bike has a specific mount and you wish to install disc brakes with a different mounting system you can purchase a disc brake mount adaptor. There are two main types of disc brake mounts:

  • IS mounts: 51mm
  • Post mounts: 74mm

Kona Process 134 27.5 (650b) 2015

Types of disc brake pads

Disc brake pads work by creating the friction that enables you to slow down or stop your bike. There are three main types of pads you can purchase at Wiggle.

Sintered: Sintered pads are the hardest wearing compound and most popular type of disc brake pad. Although they're not quite as powerful as organic compound pads, they provide excellent performance and longevity.

Organic: These pads are made of organic materials, providing the most powerful option. Although more-powerful, this compound wears out more easily.

Semi-organic: These are not always an option with after-market brake pads, but offer a good combination of power and longevity.


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Disc brake rotors explained

Disc brake rotors are strong and lightweight circular metal discs that attach to the front and rear wheels of your bike. When you squeeze your brake levers a clamping force is applied to the disc rotor from your brake pads. The resulting friction enables you to slow or stop your bike in a controlled and progressive manner.

Rotor diameter

Disc brake rotors come in a wide range of diameters (140mm to 200mm) and this aids performance in the following ways:

  • A larger rotor diameter means  you can generate more stopping force on your wheel.
  • Braking forces generate heat on the rotor and in the disc brake pads - a larger rotor helps dissipate heat more effectively and this preserves your brake pads and improves performance.

The rule of thumb for determining diameter size and performance is that for every 20mm increment in size you gain up to a 15% increase in braking power. Most mountain bikes now come equipped with 160-180mm rotors for optimal stopping power. More gravity orientated disciplines such as downhill racing and alpine riding use a 200mm rotor up front.


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Disc brake maintenance

Hydraulic disc brakes need very little maintenance. Unlike rim brakes or mechanical/cable actuated disc brakes; there is no cable to get clogged up with dirt and grime. Hydraulic brakes use a ‘hose’ to transport hydraulic fluid (could be Dot 4 or 5.1 brake fluid used in Avid, Hope, Formula and various other brakes, or non-corrosive mineral oil as found in Shimano or Magura brakes) from the brake lever to the caliper which is completely sealed.

What brands should I look out for?

The most popular brands are Shimano, Formula, Hope, Magura and SRAM. There are however numerous other brands that produce good quality disc brakes, but for cyclists demanding the best of performance, you can’t go wrong with either of the above brands.