Squeak

Problem

The squeaking of wheel brakes is an old story and was already omnipresent with rim brakes. The introduction of disc brake technology in the bicycle industry has not eliminated the problem, on the contrary. There are several reasons for this.

• The pads are new and not braked in
• The brake pads/disc are damp or wet
• The brake linings (pads) are glazed (can be repaired with sandpaper)
• The brake pads are worn or old
• The brake disk is oily (e.g. after oiling the chain or a leaking brake caliper)
• Contamination on the windshield and/or pads
• The brake disk / brake caliper settings are not correct

The rear brake in particular often produces squealing noises on the Stromer. However, the front brake is no exception. This may be due to the reasons mentioned above, but may also have its origins in the design.

At the rear, the brake disk is mounted directly on the left-hand flange of the hub motor, which functions as a resonance amplifier (drum effect). A solid, hollow rigid fork is installed at the front, which also serves as a resonance body.

As two Stromer dealers confirmed to me, the whining or squeaking cannot be eliminated permanently. Sooner or later it will return, no matter what you do. It is possible to convert the system to another product, but this is expensive and there is no guarantee of success. And Stromer prohibits fundamental changes to the brake system.

There are also differences between braking in wet or dry conditions. "Wet" is always louder! The type of brake pads also has an influence on the background noise.

Solution 1: Brake in/burn in brakes correctly

Before looking for other causes for the squealing, make sure that the brakes are braked in and, in the case of resin pads, that they are also burned in.

> See BREMSEN - 'Brake in/burn in brakes'

Solution 2: Resonance damper disk for the rear wheel

Stromer offers a resonance damper disk for the rear wheel. It is mounted between the brake disk and the motor flange. 
Practical experience: Works!

Solution 3: Use resin (organic) coverings

One way of reducing noise is to install organic (resin) surfaces. Noise reduction can be achieved at least in dry weather.

In the wet, resin pads squeal even more than the original sintered pads, at least until they are braked dry. They usually have a slightly softer pressure point, but then brake just as well as the sintered pads.

Resin linings must be braked in the same way as sintered linings, but must also be baked.
This is achieved by braking downhill and heating the brake pads to over 200 °C. This causes the solvents to outgas, achieving optimum braking performance and minimizing noise. This point does not apply to sintered pads.

> See BREMSEN - 'Brake in/burn in brakes'

Practical experience: I have been using SwissStop pads on the rear of my ST3 for 24,000 km. Together with the Motor01 Spacer the station wagon is noiseless in dry conditions. They also squeak in the wet.

Solution 4: Brake Silencer

SwissStop offers the 'Disc Brake Silencer', a spray that diffuses into the brake pad and is intended to reduce noise.

Practical experience: A noise reduction occurs with the original Stromer TRP pads. However, the effect does not last very long and the silencer must be reapplied. 

Solution 5: Copper paste

S-Ped riders also report that applying copper paste to the back of the brake pads helps.

Practical experience: None. Vibration damping is certainly possible due to the inert consistency of the paste.

Solution 6: Balancing weights as resonance dampers

The following solution is a somewhat unconventional approach.

Practical experience: None

Alternatives to the original TRP pads

> See BREMSEN - 'Spare parts....'

Topic: "Correct braking"

> Books can be written on the subject of brakes and, as with batteries and chains, there are many different opinions. An overview of the subject of brake pads, their advantages and disadvantages or suitability can be found on the page flowzone.ch or mybike-magazin.de.

> Braking also needs to be learned, not only because of the brake pads, but also to avoid accidents. How to brake correctly is explained in the Article by Sheldon Brown described.