I ride a Giant ATX 2. When my disc brakes started squeaking, I bought muc-off disc brake cleaner and used it on my discs and pads. It worked initially, but after 10km of paved road riding, the brakes will squeak when I brake hard. What's causing it?
Let's assume that the state of your brakes, discs, and pads is good. When braking hard, the frictions between the disc and the pads cause a lot of heat. After this heat reaches a certain level, the structure of the disc and pads material gets looser and the friction between them gets reduced, also making that awful noise. Make sure you always keep the disc and the pads clean and avoid long-time braking, even if it's not powerful. Better brake for a shorter time with more power, so your brakes will get some time to cool off before your next braking. Have fun out there!
I had a very similar problem. I find the Muc-off spray by itself doesn't provide a proper solution. I solved the noise by the following:
- Take the pads off.
- Clean the rotors thoroughly with some Fairy Liquid and warm water, using a dish scourer sponge, making sure you rinse it totally. Dry well. Then spray with Muc-off.
- Clean the pads using warm water and fairy liquid, use a toothbrush to scrub em well. Rinse thoroughly.
- Dry the pads then rub the surfaces with some fine sand paper for a few seconds, wipe the dust off.
- Spray a bit of Muc-off on the pads
- Reassemble - hey presto, no squeek.