It happens like this, when you least expect it, and you end up with squealing mountain bike disc brakes. Maybe you were cycling and they started suddenlyor you haven’t used your bike for a while and now the disc brakes are making noise, or you’ve just used it, you even washed it, and the next day you find yourself with the mountain bike with disc brakes that whistle, or again they whistle as soon as you start your round, then after a while they stop, and as soon as you brake they start whistling again. Not to mention when you take the wheels off to transport the bike, you put them back on and the mountain bike’s disc brakes squeal. A real nuisance. You stop, look and look again, try to spin the wheel to see if it “touches” somewhere, you try to brake by pressing on the fork, then lifting the wheel, then only with a brake but nothing, you can’t understand why MTB disc brakes whistle like that. Don’t worry: it’s happened to everyone, and there is more than one solution.
Why do mountain bike disc brakes squeal?
To understand why mountain bike disc brakes squeal, you need to analyze two things: what the squeal we hear is, and how the brakes are made. The whistle is a sound, sounds are nothing more than vibrations generated by an oscillating body. So, if the disc brakes squeal, it is because there is a vibration generated inside them. And inside them only two components can generate this vibration: either the pads, or the rotor. A disc brake, unlike rim brakes whose pros and cons we have analyzed here, is in fact made up of two pads which, when we brake, generate friction with the rotor, which instead is the part that rotates integrally with the hub, and consequently with the wheel. Under normal conditions disc brakes do not squeal, therefore they do not generate vibrations, but due to wear of one or other of the parts, due to dirt (or rather: contamination) or due to vitrification of the pads the brakes could start squealing at any moment. Let’s see how it happens and what can be done to eliminate that annoying sound.
Wear can cause disc brakes to squeal
As mentioned, disc brakes work with two pads that squeeze the rotor, generating friction and braking the bicycle’s wheels. It goes without saying that braking after braking the pads and/or the rotor wear out. Wear, i.e. the reduction in the thickness of the pads and rotor, is not normally the main cause of squealing brakes, on the contrary often you hear mostly strange metallic noises when you brake.
However, it cannot be ruled out a priori, and it is a simple thing to check: an expert eye can recognize worn pads and rotors on the fly, normally the pad lining must have a thickness of at least 0.5 mm, and the rotor must be at least 1.5 mm. If this is not the case, the worn component must be replaced and various whistling and metallic noises should disappear.
Mountain bike brakes squealing because they are dirty
Mountain bike brakes can squeal because they are dirty. Or rather contaminated. Meaning what, It’s not that they whistle because there’s mud or sand, they go away on their own and without making the brakes squeal. The pad linings are made of a porous material, which can be organic, semi-metallic or metallic, but which in fact it could absorb or become impregnated with something contaminating. What? For example of theoozing oil somewhere from the bike or found on the street, or gods solvents, degreasers or cleaners used to clean the bike (here, in the meantime, are tips on how to wash it correctly), or even some lubricants used for transmission (here are tips on how to clean and lubricate the transmission).
What to do in this case, change the pads? Sooner we can try to clean the linings (making sure before you have eliminated any oil exudes and various leaks). The rotor can be easily cleaned with a paper towel, also useful for cleaning the inside of the pad calipers. Cleaning the linings is more difficult: in this case you have to remove the pads, clean with a special product called brake cleaner (there are many brands and specific ones for MTBs), sand the pads with 1000 grit sandpaper, clean everything with a paper towel and reassemble. If the disc brakes continue to squeal there is no other solution than to change the pads.
MTB disc brakes squeal from vitrification
The last hypothesis is that mountain bike disc brakes they whistle due to vitrification. And this is the biggest problem for which the only solution is to replace the pads. What is vitrification? As mentioned, the tablets are porous and can be made of 3 types of material (organic, semi-metallic or metallic). Braking occurs by creating friction between the pads and the rotor, and the friction generates heat. Excessive heat, for example during very long braking, changes the surface of the pads, making them shiny and smooth to the touch. If this is the case, there are no alternatives: the only solution is to replace the pads.
Foto di Markus Spiske da Pixabay
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2024-06-21 07:08:18
#Mountain #bike #disc #brakes #squealing
