Putting the brakes on that dreadful squeal!

I have a 2011 VW Polo which I bought last year. I changed brake pads and discs in December after I had discovered that there was a vibration when I braked from high speed. Now when I brake there's a squeal that is unbearable. At first I thought it was because the pads were new, but the noise isn't going away. What can I do to fix it? I can't handle the noise any longer. - PJM

There are few things as annoying as the awful caterwauling of squealing brake pads. It can be caused by a variety of factors, with improper installation probably heading the list.

I recently had a chance to attend a training seminar offered by Alfred Teves Brake Systems (ATE) for dealers and workshops.

At the seminar, the importance of giving the calipers a thorough service when pads are replaced, was emphasised.

First and foremost, the inner parts of the calipers should be cleaned really well. It's not sufficient to just blow them clean - use a wire brush.

Shims are important to prevent rattles and squeals, don't be tempted to discard them unless new ones are included with the set of replacement pads. Inspect the backing plates of the new pads and use a file, sandpaper or grinder to remove any burrs, ridges, extra paint or high spots - anything that can prevent the pads from sliding smoothly in their guides.

Pads that are sticking on their guides are one of the main reasons that the second or third set of brake pads don't last nearly as long as the original, factory-fitted set.

Anything that causes binding of the pads in their guides can easily lead to the friction lining still dragging on the disc when the brakes are released.

This will shorten the life of the pad, and what's more, you'll be wasting expensive fuel to wear away expensive friction material.

When it comes to installing the new pads in the calipers, some form of high melting point grease has traditionally been used on the sliding surfaces and guide pins, but ATE has recently brought out a new product, called Plastilube, which is claimed to provide longer-lasting lubrication and prevent disc-brake squeal.

It is recommended that the guide tracks in the caliper, the sliding surfaces and piston contact area of the pads' backing plates, plus all guide pins and rails, be lightly coated with this lubricant.

It goes without saying that no form of lubricant should ever be allowed to get on to the friction surfaces of the discs or pads.

Some brake pads have specific instructions printed onto them to say where each pad is to be installed - for example "left front outer" - and these should be closely observed.

The rear brakes, whether drums or discs, should receive the same attention as the front ones at every major service.

Drums should be removed, all the dust cleaned out (dust is one of the biggest enemies of brakes!), the sliding surfaces lightly lubricated and the brakes then adjusted, after making sure the handbrake is slackened off fully.

If these guidelines have been followed, there is only a slim chance that the brakes will squeal. If they do, the suspicion must fall on the quality of the pads.

The major brake companies, in conjunction with car manufacturers, spend a great deal money to develop friction material offering the best compromise of pad life, grip, noise, non-abrasion of the disc, dust creation, and price.

It therefore makes no sense to fit cheap pads of unknown origin. Not only might they be prone to squealing and fading under heavy use; they might also wear down the discs faster than OE pads.

In the rare instances where pads from a reputable manufacturer, specified for your car - and fitted with proper care regarding caliper cleanliness and lubrication - still squeal, you will find that pad's manufacturer making strenuous efforts to help' you resolve the issue.

My impression, has been that few service centres worry about servicing the calipers because it is time consuming and will push up the cost of pad replacement to a level at which the workshop cannot compete with a service centre which has fewer scruples about the condition of the calipers.

This is the ideal kind of job for the DIY mechanic. You don't need an array of expensive tools, or years of specialised training; by just taking due care and being prepared to spend some time on the job, you will do it better than the vast majority of workshops.

There are some good YouTube videos showing how to change brake pads.