Today I'm here to tell you about disc brakes.

Bicycle brake  drum type, wheel ring type to disc brake type, advancing with The Times. The use of disc brake is more more popular,brake this kind of safety, life saving device, there is no right to failure. We intend to understand the disc brake, not judge, distinguish between good bad. The choice adoption of the system should be based on the user's own riding style, needs, budget, etc., to meet the needs of each,each has its own use.

Mechanical disc brake or hydraulic disc brake 

According to the way of brake action,said to make brake pad clamping disc media to be divided, one is the brake line, one is oil. Mechanical disc brake, by the tension of the brake line so that the brake pads in the caliper friction clamp the disc, the braking effect. Oil pressure type, with oil as the medium, pull the brake handle is to move the piston inside the compression oil, pressure  the tubing through the caliper, so as to promote the piston in the caliper, drive the brake pad clamp disc. Mechanical disc brake has its compatibility on the convenience, the general V brake handle can be universal. Hydraulic disc brake handle, tubing calipers are a complete set of products, natural traditional cable-driven brakes have no common intersection. Some disc brake manufacturers design a semi-mechanical, semi-hydraulic disc brake (semi-hydraulic), this middle line products to maintain the hydraulic caliper, still rely on cable tension, but acting is the compression piston in the caliper part.

Oil pressure disc brake advantage is that the brake output force is several times the hand force, belongs to the four two sharp brake force. Sealed property, low maintenance. Hydraulic disc brake in the use of steam car is very mature, to the picky bicycle, but involves a lot of technical problems, seemingly simple bicycle, in fact, difficult to fix. However, the oil disc brake handle has a reservoir, so the volume is relatively large, in many parts of the handlebars to compete for territory, attention should be paid to the STI type of variable speed handle,Grip shifting variable handle compatibility issues. Traditional rim brakes are also available with hydraulic brakes. And pull the mechanical principle of the cable disc brake, may be due to the length of the line itself, elasticity,shell friction other factors,the loss of braking force. In wet, rainy days, the brakes are often accompanied by squeals,some riders' backs will itch.

Tips: Some people are used to the car two wheels upside down, if the oil pressure disc brake, air, gas in the oil can run into the oil pipe, affecting the braking force. Get into the habit of testing the brakes before riding.

Open or closed system 

Oil pressure disc brake internal structure debate more,  the open closed system, the biggest focus in the oil will be hot expansion cold contraction! Oil pressure system disc brake, if the oil is hot, especially in the hot days of continuous braking, expansion too much, just push the brake pad outward, may grind, drag,even bite to death! The so-called open (oil pressure) system, for the thermal expansion contraction characteristics of oil, especially in the brake position of the oil can design an oil valve reserved space, to accommodate the increase in volume of oil thermal expansion, but also let the brake oil back flow, in order to compensate for the wear of the brake. In a closed system, the brake block is isolated  the piston the oil, so that the thermal expansion of the oil will not push the brake pad out too dramatically, so the oil must be especially careful (mineral oil is generally used). Brake pads wear out, so the disc brakes the oil can all have acuity adjustment devices in the closed system.

Tips: Oil expansion caused by calipers bite to death disc, self-assertion to let off some oil, is not the solution, but may be the risk of brake failure! It's a good idea to send it back to the car shop for a physical.

Mineral Oil DOT-approved (Department of Transportation) Brake doT-3DOT-4 is the brake oil for the disc brake of motor vehicles. The composition is to overcome the thermal expansion contraction properties. Friction creates a high temperature when braking, allowing oil to boilevaporate to produce gas. The problem is that gas is easier to compress than oil. When you pull the brake handle, you only compress gas bubbles, which cannot push the piston/brake pad, resulting in brake failure great loss of force! Dot-3DOT-4, on the other hand, have lower boiling points than mineral oils, are toxic corrosive,can m paint. The good news is that they absorb water, including water vapor  the oil can. The boiling point of oil decreases if it contains water.

Cannondale's Coda disc brake oil, a special formula developed by NASA, can withstand the heat of a rocket launch, let alone a bicycle brake! Magura was the first to use mineral oil. Its ingredients are purenon-toxic, but it won't absorb moisture wash the paint off. Advantage is used for a long time enered high temperature, braking force will not be reduced. Brake oil should be replaced regularly. DOT oil is generally recommended to be replaced once a year because it absorbs moisture. Mineral oils don't need to be renewed so quickly, but if you feel a little slack in pressure, check first. It may be time to change the oil.

Tips: Instructions oil can usually indicate the use of oil, DIY  oil change, please do not mix these two kinds of oil wrong. DOT oil corrodes the oil seals of mineral oil system svice versa. Hayes oil DOT oil for disc brake pressure. The Magura system uses mineral oil.

Floating mounting Caliper or Fixed Caliper

There are two kinds of disc brake calipers, a fixed, another caliper installed on the frame fork, but also can be active, generally transverse slip. In the development process of bicycle disc brake, the formation of two schools of theory. Floating caliper fixed way "can be horizontal slip" design,unilateral disc brake brought about by the negative effect, is closely related. But it has its advantages, such as tolerance problems of the frame, the front fork even the thickness of the coating on the assembly seat, which can affect the accuracy between the disc brake pad, so it often relies on washer/spacer to remedy correct. Some floating calipers have a special emphasis on the correction disc brake block parallel, flat effect,do not worry about tolerance issues.

Tips: The paint on the disc brake seat of the frame front fork is usually filed off during disc brake assembly, because its thickness will also form assembly tolerances. However, please handle with care, so as not to damage the flatness of the metal, which may be self-defeating.

Single-sided Actuated or dual Actuated

Unilateral action bilateral action, braking, not only exist in hydraulic mechanical disc brake, but mechanical disc brake is mostly unilateral action. Unilateral action, that is, only one side of the piston will push the brake pad pressure, friction on the disc, the other side of the brake pad is waiting for the opposite brother to push the disc over, so that both sides of the running-in effect. So there are floating caliperfixed caliper theory.

Bilateral action, naturally refers to the caliper with two opposite pistons, so that the brake pad  both sides together to clamp the disc. At present, the piston number of disc brake caliper has 1 (unilateral action), 2 (a pair), 4 (two pairs), up to 6 (three pairs), the number of piston is not necessarily equal to the number of brake pads, because there are two pistons on one side, but it is a long brake block; The two brake blocks are not necessarily bilateral clamping, as they may be unilateral. Such as Magura Gustav M is unilateral action, you see its piston, brake pads have a few? Mechanical disc brakes with bilateral action will be mostly the work of Taiwanese manufacturers such as RST, Shen'll, zhong ying. But the new face of Kongying set company, has made a "single drive, bilateral clamping" Winzip M1.

Tips: simple test: set the disc brake buy the car with disc brake, the car is parked, pull the brake handle, eyes staring at the disc brake pad, observe the clamping situation, especially the unilateral action system, the disc is pushed fold distance is too obvious, whether the swing?

Brake Pads: Metallic or Organic Pads

Brake pads of different ingredients materials have different friction coefficients. The organic brake pads are made of Kevlar mixed with fiberglass, without any metal powder. It can have a strong braking force, yes, but in high temperatures humidity, the force loss is more severe than a metal-formulated brake pad. The advantage is that this brake pad will not conduct heat, relatively do not worry about the thermal expansion effect of oil, so in the closed oil pressure system, very ideal. And metal brake pads, most of which contain copper iron powder, more wear-resistant, but also more not afraid of dust mud affect the brake force. But the heat transfer effect is too good, naturally suitable for open oil pressure system. Between disc internal external brake pads, are generally emphasized to parallel, equal spacing, assembly will be carefully calibrated, in order to achieve the ideal action mode of synchronous, equal force clamping on both sides. This aspect emphasizes the principle of bilateral moving callipers. And some floating calipers unilateral action disc brake, disc is relatively close to the fixed, non-active side of the brake pad, even slightly contact, the wheel is not static space rotation, there is friction, also refers to virtually reduce speed.

Tips: There must be a run-in period between the disc brake pad of the new disc brake. With the new disc brake, it's a little dangerous to try it out.

Disc Rotor 

The main task of the disc is to be tortured. The material is mostly stainless steel, some manufacturers do aluminum alloy disks, said that the heat dissipation effect is better,some people do titanium carbon. Disc disc must be equipped with "disc brake drum", generally the traditional wheel brake to be replaced by disc brake, only "whole " replacement,with a special adapter. The compatibility of flower drum disc may also need to be noted. The standard disc has six screw fixing holes. In the early days, there were four holes. Cannondale Coda is still in use. The Hope in the UK has a 5-hole model, but there are also generic 6-hole models. The Bees in Germany are not screwlocked but rather "quincetooth"ratchet fixed, with their own flower drums to use. Disc sizes are not standardized either; 160mm is the most common,Hope has sizes as small as 130145mm.

In principle, the more intense the ride, the bigger the disc, because the brakes are more powerful,are usually larger at the front smaller at the back,equal at the front back.

Tips: Usually wipe clean the dust on the dish, pay attention to wipe with alcohol; Lubrication maintenance, disc to avoid greasy, slippery, not brake hope.