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Myth number 1: Braking is unnecessary.
Wrong! Those who work with new Brake pads (or even discs) on a mountain bike tour risks overheating the system too early. Warped discs, glazed pads and greatly increased wear are possible side effects. Only a carefully calibrated brake will achieve full braking power, maximum temperature resistance and a long service life.
Or to put it the other way round: in the worst case, a poorly braked system has 50 per cent less braking force than it should have. How to do it properly? In short: brake from fast to slow for 15 minutes, but not to a standstill. You can find more detailed instructions here: Braking MTB disc brakes correctly.
Myth number 2: A four-piston brake is stronger than a two-piston brake.
Also wrong. The last one MTB disc brake test from BIKE 5/2019 proves that it is not the number of pistons that matters. All other things being equal, it is not the number of pistons but the piston area that determines how high the braking force theoretically is. This surface area can be larger with four pistons, but does not have to be, depending on the brake model. In the end, the most important factor is the coefficient of friction provided by the brake pad compound.
Myth number 3: Using the wrong brake fluid will destroy the brakes.
That's right! In hydraulic MTB disc brakes, mineral oil sloshes in some lines as a medium (e.g. Shimano, Magura), in others the so-called DOT brake fluid (e.g. Sram, Hope) based on ethylene oxide and alcohol. The different chemical properties of the two types of fluid require special seals that are not compatible with the other in the long term. If the wrong fluid is used, there is a risk of damage to the entire brake due to the destruction of the seals.
Myth number 4: If the brakes stink, the pads are burnt.
No, on the contrary: they usually brake better. Most organic and even some sintered brake pads emit a pungent odour during the first few rapid descents, often associated with a reduction in braking efficiency. However, this process, known as "initial fading", is part of the braking process. The odour comes from binding agents that evaporate from the pad at different temperatures. Once the brake pad has been braked, the braking effect remains constant and there is no longer any odour.
And even later, a hot brake does not mean a problem. A good indicator is the discolouration of the brake disc:
Orange-brown discolouration: Everything OK!
Purple to rainbow-coloured: Brake got too hot.
Myth number 5: Organic brake pads are stronger than sintered brake pads.
It depends. The last one Test of MTB brake pads (BIKE 5/2017) showed: On average, organic pads were stronger in the tested Shimano XT brakes, roughly equally strong in the Sram Guide and weaker in the Magura MT4 than sintered pads. The advantage of organic pads: They usually brake more quietly. However, they are often not as stable and durable in wet conditions or on long descents.
Myth number 6: Sintered pads last longer than organic ones.
No. After 1000 dry test bench brake runs, a sintered brake pad won the last race. Pad wear test in BIKE 5/2017. Behind them, four organic brake pads also scored full points. In a direct comparison, three out of four sintered pads fell a few percentage points behind the respective organic models from the same manufacturer.
When changing the brake pads, the braking force may not be optimal. The surfaces of the new pads and the brake disc must first adapt to each other, "get used to each other" so to speak. After changing the brake pads MTB disc brakes braked again see also myth number 1.
When changing from organic to sintered brake pads (or vice versa), the brake disc should also be changed in order to achieve the optimum braking effect.
Fact number 1: Brakes and driver must fit together
Of course, most bikes are already fitted with brake systems. But this is often exactly why setup problems occur. The choice of brake is not just about weight or disc size. Three fundamental factors should have a decisive influence:
- Weight of the driver
- the main Field of application of the bike
- the driving Ability
For example, a 50-kilo downhill rider may need the same brakes as a 100-kilo weekend hobby rider. In the end, it's all about safety on the bike.
Fact number 2: A large brake disc is not always a better brake disc
If the mountain bike brakes do not deliver the desired performance, the first impulse is: I need larger brake discs! The following 5 factors influence the braking force:
- Weight of the driver
- individual Power in the hands
- Braking frequency (Downhill or uphill trails?)
- Braking time (long descents or flow trails?)
- Brake disc size
The braking process is a combination of friction and heat. The maximum braking effect is achieved within a certain temperature range. If the combination of the factors above causes the temperature to exceed or fall below this range, the braking system will not perform optimally. In short: If the 200-millimetre disc does not get hot enough, it will not brake any better than a 160-millimetre disc.
Fact number 3: Brake fluid is a chemical
No matter whether DOT or Mineral oil, both of the brake fluids used are - unlike chain grease or bearing grease - substances that require a little attention when handling.
- Both brake fluids are Harmful to the environment.
- Both substances Damage to the skin - wear gloves at work and be careful.
- DOT and mineral oil must Properly disposed of as hazardous waste become.
Fact number 4: Brake fluids have a decisive difference.
In myth #3, we explained that the wrong brake fluid can destroy the brake system. As the manufacturer Sram shows in this video, DOT and mineral oil behave fundamentally differently. Whilst oil and water are not known to combine, this is not the case with DOT (alcohol-based). Over time, a DOT-filled brake system absorbs water (humidity, driving in the rain, etc.). Braking performance slowly decreases because water and DOT fluid behave differently at high temperatures. Consequently, the brake fluid should be replaced regularly.
This is different with mineral oil. Therefore, such brake systems require less maintenance and are suitable for bikes that are not constantly ridden and maintained, i.e. for the weekend biker or the rider with a small fleet.
Sebastian Brust
Editor
