Hi,

I bought my son a Cube Aim for Christmas (he paid for half before anyone calls “spoilt child” 🙂 )

It soon had some chain lubricant sprayed on the chain. Now I’ve read up on bikes with disc brakes I understand this is not the right thing to do as it will end up on the disc (rotor?)

So he reports back that his brakes are screeching, and some googling seems to point to contaminated discs and pads. I think therefore I need to remove pads and rotors, sand down with 120 grit and give a good clean with brake cleaner? So why am I writing this if I think I might know what to do?

Well, I went out to look / ride the bike and am a bit confused. Front brake perfect – no noise and instant stopping (wasn’t like that in my day), so once I’ve taken teeth off the pavement I try the rear. Just a gentle squeeze on the rear brake lever causes a horrendous screeching, but the thing I don’t understand is that it just doesn’t sound at all like it is coming from the rear of the bike or the disc / pads. it 100% sounds like it is coming from the bike frame and to my ears seems to originate from about 9″ behind the handlebar stem.

I don’t want to start removing things unnecessarily, so I though I would add this post to get some expert opinions.

1) Are my ears just deceiving me and is this what the obvious answer seems to indicate – contaminated disc?
2) If it is what is the best method to follow? Is it simply to remove, sand with 120 grit paper and then use brake cleaner to clean both discs and pads?

Thank you in anticipation for any advice that can be given, I really want to learn a few of the basics rather than just keep taking it to the bike shop – and I intend to educate my son too!

You can get noises resonating through the tubes of the frame.

Pull the brake lever while looking at the caliper to make sure the pads are moving. The disc is easily cleanable, even scrubbing with plenty of hot soapy water will get them clean. Or get brake cleaner from Halfords, Toolstation etc.

If the pads are lightly contaminated then you might save them, if heavy then just fit new ones and bed them in properly. If the bikes getting a lot of use then you might as well buy packs of pads on the web from Uberbike, Superstar Components etc.

It sounds likely that the contamination is causing the noise. Don’t be deceived by where you think the noise may be coming from, that can be deceptive. You can clean the rotors but contaminated pads usually need replacing. Before you do so, just check that the caliper and rotor are tight/properly aligned as this can cause squealing.

As said above…don’t sand the rotors just clean them….check alignment of callipers. Also a smear of copper grease to the back face of the pad (mating surface with piston) might help but be careful not to get on the pad

Just to show how unsure I am can you clarify what you mean about aligning the callipers please. Do you just mean ensure that they are “straight” and the rotor is going directly through the centre of the pads?

Yes, there should be a small even gap between each pad and the disk. I suggest you might want to figure out the make and model of the brakes and search for the service manual online, youtube might also have some useful videos for you.

Where are you op? Might be someone local to give you a hand?