Got a technical question? Ask TRW’s expert

This month Brian Newell talks about a subject very close to his heart – brake noise!

Q: I have just fitted new brake pads to my car and am experiencing a great deal of squealing coming from the brakes. I read in an automotive magazine that this was because I didn’t smooth or ‘de-burr’ the edges of the brake pad with sand paper before fitting. Is this correct?

A: If the edges of the brake pad need smoothing or de-burring before fitting, then I would seriously question the quality of them! The noise is likely to be caused by not fitting new brake discs at the same time. When you change the brake pads, you should always change the discs at the same time.  As the brake pad and disc wear, you usually get two ridges on the inner and outer edge of the disc. If you do not change the discs at the same time, then the new brake pad is likely to sit ‘on’ these ridges and not make proper contact with the disc, therefore being less efficient and generating undue noise. Also, make sure the caliper is clean and all moving parts such as the slides and pins have free movement.