I have a new Amflow Carbon PL Pro. It would be a great bike if it weren't for...
I've done my first 10 tours (13,000 metres of elevation gain and 320 km). I've taken the bike to the repair shop three times, watched three videos about the well-known Magura problem and spent at least five hours in my workshop myself.
-Cleaned and finely sanded the brake discs.
-Sanded and replaced the brake pads.
-Aligned the brake caliper countless times.
-Reduced the amount of brake fluid.
-Pushed the brake pistons all the way in countless times.
Nothing helped. The brakes continue to squeak and roar merrily along. It's almost unbearable!
If it's a defective part, that can't be normal on a € 10k bike, can it?
I think it is worth separating the symptoms of brake problems in order to focus on the solution.
Brake pad/calliper alignment problems will cause brake rub and if more extreme vibration you can feel through the lever...as well of course as poor braking response. None of that will cause squealing on brake application.
Noisy pad on rotor problems are due to poor grip between the pad and rotor. The classic causes for that are
1. Contamination on the rotor. That can be caused by a variety of aerosol cleaners/polishers even if sprayed well away from the bike but in a closed space. It also includes some general non aerosol cleaners and of course oils. If using any cleaning/lubricating products on a bike it is best to cover the rotors first. Even touching the braking surface with your hands can contaminate the rotor. Other causes include road/exhaust contamination if the bike is carried on the back of a car/van but probably by far the biggest cause is poor brake pad bedding in procedure. Sintered pads are the hardest to bed in properly.
2. Using mismatched pads and rotors. Some rotors are designed only for resin pads.
So how to bed in pads? The process involves transferring a sacrifice layer on the pad to the rotor whilst a voiding heating the rotor. So the best way to do that is to spend 10/15 minutes on a quiet section of road riding at a moderate speed and then applying one of the brakes hard until you nearly come to a stop and then release. Repeat several times. After each application you should feel the braking efficiency improve. Repeat with the other brake. The classic sign of not having done that correctly is a black deposit on the rotor......caused by heat!
How to get rid of contamination? Use shop towel with a section soaked with IPA and rub both sides of the rotor using more clean towel if necessary until that wiping leaves no marking on the towel. (In my experience using supposed brake cleaner fluid for this is worse that useless!). I see no reason to use any abrasive material on a rotor unless it is scored. I have never sanded a rotor!.
Pads can be cleaned firstly with IPA and a cotton cloth, then with c 1200 grit wet and dry, then with IPA again. Dont use sand paper!!
You will need to bed the pads in again now, although it will be quicker second time a round.