Some opinions about disc brakes and rim brakes road bike

Brake force

Let's talk about the braking force first. As long as the wheel can be locked, the total braking force is enough. The main limitation of the braking force output is the tire, not the type of brake. However, this is also limited to the dry road conditions of daily riding. In the humid environment, because the speed of the disc brakes off the water film is fast, the surface of the brake disc is almost no water, and the braking force is obviously greater than the ring brake.

The reason why the brake force of the disc brake is better is that the brake response of the disc brake is faster.

Brake response

The disc brake uses resin or metal to rub the sheet with the metal brake disc, and the hydraulic energy can amplify the braking force according to a certain ratio. This determines that the response at the beginning of the brake will be better, and the initial stage of the brake can be pinched. It outputs a large braking force, and it is easier to lock the wheel at the end. Compared with the use of the wire pull clamp and the 1:1 output brake force, after the brake rubber contacts the rim, the deformation of the wire tube and the clamp itself will always cause a slight delay in the brake force output; in a humid environment It is necessary to scrape the water film to output the braking force, and the delay is even greater.

The disc brake can reach the critical point of locking in the middle section, and the critical point will be clearer than the rim brake; the rim brake will basically reach the critical point until the end point, so it will feel that using the brake brake to lower the brake will More tired.

Because the initial braking force is greater and the response is faster, the use of the disc brakes will give people more confidence in high-speed downhill and cornering, and it will make handling easier. These two factors determine that the brake point of the disc brake can be greatly delayed before the cornering, and the average speed when passing the same corner section can be higher than the rim brake.

In addition, an interesting part of the disc brake is that the size of the brake disc can be selected according to the user's weight and riding style to adjust the braking force and the brake linearity, which is an advantage that the disc brake does not have.

Thermal attenuation

In the case of relatively severe working conditions or long-time brakes, the brake oil of the disc brakes will boil and generate a large number of air bubbles, resulting in a decrease in the brake force output. Since DOT oil has a higher boiling point than mineral oil, it has been Shimano's weakness in heat decay resistance, so Ice-Tech is needed to assist in cooling. The thermal decay of the brake is not as obvious as the disc brake.

Reliability

Under the downhill limit conditions (for example, the newcomer who does not dare to landslide, all the way to the brake), the reliability of the disc brake is obviously better than that of the rim brake, because there is no risk of explosion of the box like the rim brake, and the user can be put in any way. Returned safely to the foot of the mountain. However, in daily use, there are also many feedbacks on various strange problems of the road disc brakes (mainly concentrated on the Shimano hydraulic electric hand change head), such as the oil leakage of the clamp piston. So in the link of reliability, it can be said that it is a tie.

Feel

The feel of the rim brake clamp depends entirely on whether the wireline core is smooth, the technician's installation and adjustment technology, and even the frame design of the frame will also affect the sense of the opponent. As long as the oil filling operation is correct, the disc brakes will have a consistently excellent feel, and the difference in the level of the parts will not bring about a large difference in feel. So in this game, the disc brakes are over.

Weight

In addition to the weight gain of the disc brake kit itself, the disc brakes and wheel sets are heavier than the rim brakes (of course, special cases are not excluded).

Price and cost of use

The same series, the same level of the road bike, the disc brakes will be more expensive than the rim brakes, which everyone knows, so we just talk about the later use costs. In terms of medium, the hydraulic disc brakes only need to be emptied regularly and the brake oil is changed once a year; the line group of the lap brake can be used for about two years (regardless of the disc brake or the lap brake, often in the case of high temperature or downhill conditions, the maintenance period is halved). If you use a top-level line set, the use of the disc brake is lower; if you use a low-end line set, then the cost of the rim brake is lower.

It is very simple to replace the film or brake glue, and everyone can do it themselves. However, if you change the line pipe or brake oil, you will usually go to the bike shop. Since the rim brake replacement line set needs to be disassembled and threaded, the maintenance time cost of the rim brake should be higher.

In the case of brake rubber and fasteners, if the high-end carbon rim brake rubber is used, the obvious cost of the rim brake is higher. Nowadays, the special brake edge design of the carbon rim will also accelerate the consumption of the brake rubber. The rim brake rubber itself is not cheap.

However, the disc brakes only consume brake discs, and the steel discs are very durable; the disc brakes consume expensive carbon rim, and the aluminum coils do not have these troubles. So taking this into account, the cost of use: the rim brake carbon rim > disc brake > rim brake aluminum rim.

Whether you need to upgrade or choose a disc brake mainly depends on your personal needs. If you like the thrill of high-speed downhill, or a newcomer who has just entered the pit, and is not good at controlling the rim brakes, then the disc brakes can give you more confidence; if you are more like to challenge KOM, the usual road conditions are mainly flat roads, the rim brakes are more suitable for you.