Problems with brake discs

Question

I recently bought a new bike. It is a Scott bike with disc brakes. The bike went in for it's service and now it has problems braking. As soon as I pull the brake leavers the front brakes makes a loud squeaking noise. The front brake disc is a blueish color from trying to brake. The back brakes works perfectly. I took it back to the people who serviced it, and they are unable to solve the problem. Do you maybe know what the problem could bee and how to correct it?

Answer 1

It sounds like your brake pads are contaminated with detergent or petroleum (oil) products. If so, you need to replace them.

This is a common problem, which can be solved by washing the brake rotors with IPA, and replacing your brake pads. It sometimes happens that a pad will get contaminated by chain lube or other common bike lubricants during the washing process of a bike service, and should be no big deal to fix.

As this is something that any shop worth 2 cents should know, they are either incompetent, or dishonest with you.

Answer 2

There are heaps of posts on the Internet with this problem. As @zenbike suggested, contamination of the pads is the most common cause and replacement is the only real option. Other causes are heat damage to pads (Glazing), warped disks from mechanical or heat damage. In some cases, it's just something that happens for that bike - Juicy 3's are really prone to it it you believe the Internet and all you can do is buy ear plugs.

What you do depends on your budget and skills and spare time. Heres a couple of suggestions

1. Clean the discs, and replace the pads. If you cannot afford to replace the pads, "burning" them is one thing I have seen suggested, as had a light sanding (to remove glazing) - neither have ever worked for me.

2. Set the disk caliper - if it's not sitting right this can cause squealing. Read the manual for the brakes, but essentially it involves Loosen mounting bolts, apply the brakes softly, and gently tighten the bolts 1/2 turn each at a time until tight, while rotating the wheel. The idea is to get the pad/disc interface perfectly aligned. You can check visually by applying the brakes while watching the gap between the pads and disc. The pads should be perfectly parallel to the disks at the time they make contact.

3. Try a different pad - e.g. a softer pad, different material - I replaced my metallics with Organics and that seemed to help. Trying a different brand can't hurt.

Given it appears that it was fine before going into the LBS and noisy after, the most likely thing is contamination.