Warping front discs
 

Hi I have a 2003 s40 that keeps warping the front discs. Last time I changed them I fitted new calipers but they are starting to warping again. Any idea what can be causing this. Thanks Bob

Are you sure it's the discs warping, have you checked runout with a dial gauge?
What are the symptoms, usually it's the brake pedal pulsing but there could be many other problems...disc mating suface not cleaned properly, stuck guide pins, worn balljoint(s) etc etc

Are you using genuine discs & pads? Aftermarket ones don’t last.

Heavy braking can warp discs.

Keeping your foot on the brake pedal whilst at lights doesn’t allow the heat to dissipate, which can warp discs. Putting the car in neutral & taking your foot off the pedal or using the handbrake with your foot off the pedal will allow the heat to escape.

What are the symptoms exactly?

If the discs are warped this can be caused by your braking style, as has been mentioned, but it can also occur if the hub mating surface isn't spotlessly clean and free from any dirt or rust when you mount new discs. Cheap non-branded pads can cause problems too.

But there are other causes of vibration during braking. If the callipers are sticking a bit and not completely free then you'll get some vibration. Also if there's any brake debris preventing the pads from moving freely. Or if a calliper or carrier is loose at all.

Another thing to check is that the calliper slide pins are completely free to move, and well greased with an appropriate lubricant. If not this will cause uneven pad pressure and hence vibration.

Wear in the suspension and steering can do it too, as can tyre problems.

Lastly, are you fitting decent branded new discs? On stuff like this the motto "buy cheap, buy twice" was never truer!

Jack