GUIDE
AGAINST NOISES

2.1 Normal operating noise

Braking noises occur when kinetic energy is converted into heat and vibrations during braking. These vibrations can lead to noise. Noise cannot entirely be prevented, especially with high-performance braking systems. They are not in general a sign of a malfunction. Nevertheless, MAGURA takes countermeasures in the development of components to minimize normal operating noise. New developments such as the SPORT brake pad compound and the GUSTAV brake system with particularly stiff, 2.5 mm thick brake rotors reduce the likelihood of noise. In extreme cases, contact your MAGURA specialist dealer to clarify whether the noise in your case can be considered normal operating noise. In addition, the following explanations offer you helpful approaches for solving the problem yourself. In many cases, noises can be rectified with little effort.

2.2 Noises when the brake is not applied (riding noises)

If noises occur when the brake is not applied, the cause is in many cases grinding components. Check the following factors to resolve the problem.

Check the alignment of your brake caliper

Correct alignment of the caliper is essential to prevent grinding. The caliper must be at the correct height as well as centered and parallel above the rotor.

Check the fill level of your brake

If an initial adjustment of the brake caliper does not help, we recommend first checking the fill level of the brake. If there is too much oil in the brake, the air gap between the brake pad and rotor can become smaller, making it more difficult to adjust the brake caliper grind-free. To correct an excessively high fill level: Remove the brake pads, open the bleed screw on the brake master, insert the syringe with hole and push the brake pads back into their original position. Then close the bleed screw again.

Clean the brake caliper and pistons

Keep the area around the pistons of your caliper clean to prevent premature wear and to allow the pistons to move freely. Use some water and a clean lint-free cloth to clean your caliper and the area around the piston first. The use of solvents is not necessary. 

Check the piston movement / mobilization of the pistons

Whether before the first installation, after a long period of storage, after the winter break or simply now and again: it can happen that individual or several pistons in the caliper move sluggishly. Unevenly extending pistons can cause one or more pads to rub against the rotor and generate grinding noises. 

Check the trueness of your brake rotors

Another reason for a grinding brake can be a brake rotor that is not running true. A good indication of this may be that the grinding does not occur permanently, but periodically. 

There are various potential reasons for a brake rotor running out of true: 

–    Bending / damage
–    Incorrect installation
–    Contaminated rotor mount on hub
–    Defective rotor mount on hub

How to straighten an out of true brake rotor
The brake rotor can be carefully straightened using suitable tools. Alternatively, carefully bend the brake rotor by hand using a clean cloth. Only very slight bends can be corrected in this way, otherwise the durability of the brake rotor may be impaired.

Note: Before straightening your rotor, make sure that the rotor is actually bent and that the rotor mounting points on the hub are not damaged or contaminated. 

Check the installation of your brake rotor

To avoid uneven installation with 6-hole brake rotors, turn them briefly by hand clockwise as far as they will go before finally tightening the rotor mounting screws. This centers the brake rotor over the mounting bolts. 

Then tighten the rotor mounting screws crosswise to the correct torque. 

Check the mounting points

Incorrectly angled or contaminated mounting points for the caliper and brake rotor can make correct adjustment and quiet operation impossible. Before fitting your brake rotor, make sure that there is no paint or threadlocker residue on the rotor and caliper mounting points. Residues can lead to ’tilting’ of the respective component.

Check your mounting interfaces for flatness.

Incorrectly angled PM/IS sockets or rotor mounts can make correct alignment impossible. Specialist dealerships can mill brake caliper mounts flat.

Note on the design of the MT7 and MT TRAIL SL

Please note that the 4-piston brake calipers of the MT7/MT TRAIL SL brake systems have a lower retraction due to their design. The reduced retraction is a key factor in the award-winning performance of the MT7 and enables, among other things, a shorter free travel of the lever blade. The requirements for a grind-free alignment of the calipers include optimum mounting points on the fork and frame as well as precise adjustment of the calipers. The MT7/MT TRAIL SL calipers can be easily distinguished from the MT5/MT TRAIL SPORT calipers by their color: MT7: Mystic Grey, MT TRAIL SL: Chrome, MT5 and MT TRAIL SPORT: Black

Note on the bicycle as a complete system

In addition to the brake system, also check other components of your bike for a possible increase in performance. The torque settings of thru axles/quick releases (wheels), bearing play of hub and frame bearings, components on forks, wheels, frames and brakes, among other things, can cause performance restrictions due to various factors. In unfavorable constellations, noise (vibrations) or grinding may not be completely avoidable.

The following list is not exhaustive, but offers you some often overlooked examples that can influence noise development, but at first glance have nothing to do with the brake itself. Noise can potentially be positively influenced by:

– Quick-release axles with higher clamping force
– Changing the tire pressure – Changing the tire profile
– Changing the insertion depth of the seat post
– Changing the spoke tension
– Changing the combination of different components
– Loosening the brake rotor, rotating it on the hub by one or two mounting points
– Varying the torque values within the permitted rang

2.3 Noises when the brake is applied (braking noises)

If the noise occurs while the brake is being applied, the problem usually lies in the development of vibrations of various frequencies. It is also possible for other components to vibrate. Noises ranging from high-frequency squealing to low-frequency (perceptible through handlebars) jerking are possible.

The underlying mechanism for many of these noises is the so-called slip-stick effect. In this effect, the pads and rotors alternate between static and dynamic friction in rapid succession, which leads to corresponding vibrations.

Note: Squealing can occur more frequently and more intensely in wet conditions. This can be normal. As a rule, the squealing should decrease as soon as the water has been displaced or evaporated from the brake rotor during the braking process. 

Check components for play

If there is play in other components of the bike, this can lead to noises during the braking process. As these noises occur during the application of the brake, the brake may be mistakenly interpreted as the cause of the fault. Therefore, if you have noise problems, check that your components are correctly fitted and that there is no excessive play. Typical suspects are the wheels, hubs and axles, the fork bearings, the headset and the rear triangle bearings. Also check that the caliper has been fitted correctly and that the bolts have been tightened to the correct torque. Also check that the brake rotor has been fitted correctly and that the bolts or the Centerlock lockring have been tightened to the correct torque.

Check pads and rotors for wear

Worn friction partners can promote the development of noise. When metal brakes on metal, it is already too late. Therefore, check your rotors and pads regularly for wear. 

Check for glazed brake pads

Glazed brake pads are characterized by a hardening of the pad material, which can lead to reduced braking performance and noise. Glazing can be recognized by a smooth and reflective pad surface. Glazing can be caused by an excessively high temperature of the brake pad (excessive strain on the braking system) or insufficient brake-in. The only remedy for glazed brake pads is to replace them. Grinding down the surface has no effect. Observe the respective break-in recommendation of your brake system and avoid excessive or insufficient load on your brake by selecting the right components to prevent the pads from glazing.

Excessive or insufficient load of the system

An excessively or insufficiently loaded system can cause noise. Excessive demand on the brake system can cause the friction partners (pads and discs) to heat up considerably. Overheating reduces the friction coefficient of the partners and a higher contact pressure of the pads is required for the same braking force. In other words, we pull harder on the lever and there are more vibrations. Insufficient demands on the braking system can lead to glazing of the pad surface due to local temperature peaks, among other things. Ideally, prefer intermittent braking as opposed to continuous grinding, and avoid braking operations with insufficient (“too hesitant”) braking power for the overall system. If possible, always use the front and rear brakes together. Choose the right rotors, rotor diameters and pad compounds for your area of use, your system weight and your riding style. The brake rotor size in particular is a key factor in preventing overheating. However, bigger does not necessarily mean better: you can find more information on the sweet spot of rotor size here. In addition, insufficiently loaded brake systems can lead to an increased build-up of grime on the rotor and pads. This in turn can cause noise.

Choice of components

In addition to their different performance characteristics, the noise level can also be influenced by the choice of brake rotor and brake pad compound. Stiffer brake rotors can help to prevent vibrations, for example, or prevent a previously occurring oscillation by changing the natural frequency. You can find an overview of our brake rotors here. The same applies for the choice of brake pad compounds. Compounds optimized for braking power such as the Race compound tend to generate more noise, while all-rounders such as the Sport compound reduce noise. You can find an overview of our brake pads here.

 

Outro

If you continue to experience noise issues, you can contact your local specialist dealership or send us a message on Facebook or Instagram. Our social media team will be happy to help you with case-specific assistance or refer you to the right contact point.

To conclude, we have summarized some do’s, don’ts and common myths for you below. 

• The overall goal of noise elimination is to shift the vibration frequency to another, inaudible/not perceptible spectrum (avoidance of resonance frequency). Small measures such as changing the tire pressure or larger measures such as changing to a different rotor diameter can help. The individual case must always be considered.
• Do not use copper paste! Although the “adhesive and damping” properties can temporarily reduce vibrations, there is also a risk of contamination of the friction partners and damage to the brake pistons. It makes more sense to find the underlying problem and to remedy it.
• Do not lubricate your pistons from the outside! Make sure you keep the inside of your caliper clean. Lubricating the pistons from the outside is not necessary – the pistons are automatically lubricated from the inside – and can even lead to problems. On the one hand, there is a risk of contamination of the pads and the attraction of dust and dirt; on the other hand, excessive lubrication from the outside can even impair piston retraction.
• Never overfill your brake! Overfilling can damage the system to the point of total failure and also leads to an insufficient gap with fresh pads and rotors.
• Do not use third-party products! Other manufacturers use different rotor thicknesses, different friction ring designs or different pad compounds, for example. We are unable to test these combinations and therefore cannot approve or recommend them for use. At best, the function is reduced by a suboptimal combination; at worst, there is a risk of total failure.
• I can increase the distance between the pads and rotor with a thinner rotor. Wrong! In open systems such as our MT and GUSTAV disc brakes, the distance between pads and rotor is determined by the design of the caliper around the piston seals. After pad wear and/or actuation of the lever blade, the original distance between the pads and rotor is reset.

As a US customer, you can order MAGURA spare parts directly from magurausa-shop.com. Or you can use our worldwide dealer locator.