Pulsating and screeching after changing disc brake pads

Question

Please bear with me, as I am very new to bicycle maintenance.

I changed the brake pads in my front brake (Tektro Auriga on a Rockrider 540 bicycle), as I was unhappy with the braking performance and couldn't seem to improve it. It came with E10.11 brake pads and I changed them to P20.11 ones. (It should have come with A10.11, but that's not what I found ...) These had much better reviews on Amazon, with many people saying that the braking performance is noticeably better.

Unfortunately, now there is screeching and pulsating when using the brakes. What can I do to improve this?

---

I am certain that I did not contaminate the pads. I was very careful when changing them.

When changing the pads, I cleaned the rotors thoroughly with 70% propanol.

I performed the bedding-in procedure as instructed: Speed up as much as I can, then brake hard, but do not stop. Do it at least 10 times. I used some water on the brakes before bedding in, as suggested in this Park Tool video.

Strangely, if I pour some water over the brakes, then they become smoother and the screeching disappears for up to an hour. After that, everything is back to how it was.

After changing the pads, and for a second time after bedding in, I adjusted the brake calipers by loosening the screws, pulling on the brake lever and tightening the screws. The rotor looks parallel to the pads. The rotor is true, as far as I can tell.

I am quite disappointed about the outcome of this experiment in changing brake pads, and I would appreciate any advice on how to get rid of the pulsating, if not the screeching.

---

The only advice I could find on how to deal with this was to lightly sand the rotors, as well as the pads. I am somewhat reluctant to do that after reading that this could worsen the pulsating. I do not have the tool to remove the rotor, and I am worried that I could not do the sanding well enough while the rotor is on the wheel.

Answer 1

Unfortunately you have done nearly everything possible. Some brakes/forks/frame/pads/disc combination just do not work nicely.

The one remaining thing you have to change is the disk. As the pads bed in, they lay down a thin layer of pad material on the disk, it is the microscopically thin layer that allows the braking to occur. If the bedding in is done poorly, the layer is uneven, and further bedding in may not even it up. Changing pads means the material laid down on the discs may not bed in with the new pad material. Sanding the pads disrupts (I won't say removes) this microscopic layer, allowing a new layer to be laid down when bedding in again. If the new layer is laid down evenly, the brakes will not squeal.

A final option that may (or may not) work it to change the disk itself. The obvious choice is a different type, but even this is no guarantee of quite brakes.

You really have three choices - go back to you old pads (They may now squeal), tackle the disk (sand or replace) or live with it.

Use a fine (400 or even 1000 grit) wet and dry sanding paper. This can be done with the disk in place, but is easier if you remove it. There is no guarantee this will work, new discs are sometimes the only thing you can do.