What, new discs everytime ????

[tigga]

I have been told by a friend that when i renew my front brake pads, i must get new discs too as they are  'floating-pads '   ( ? )   is this true - yr 2000 bmw 318ci ?

[Impret-Sir]

I dont know if your car has floating pads in your disc brakes or not, but it makes no difference, you only need to change the discs when they are excessivly worn, chck with your finger nail to see if there is a noticable 'lip' round the edge on the front. If not, they are probably ok, you dont say how many miles the car has done, or if the discs are the original ones, but on a five year old car its not impossible that they need changing now, but what sort of calipers you have, floating or not, does not determin this. Does you friend work for Kwik-Fit by any chance?

[tigga]

ha ha kwik fit ! i know what you mean, but as for mileage it has 50k on it, but it has been well looked after with full dealer service history if that can give any indication ?.

Otherwise as you say, i will take off a wheel and check for myself, Thanks for your help.

[BillyNoMates]

Discs should only need replacing if they are worn below the minimum thickness, warped or excessively scored. The only correct method for determining if discs are worn is to use a vernier caliper or similar and comparing against the manufacturers spec/Haynes manual. Scoring can be checked visually and by 'feel' and warping by using several thickness measurements or a dial test indicator.

[Shaygate]

What causes discs to warp ? I have driven my car (Skoda Octavia) for 54,000 miles from new and its last service was told that my discs were warped (symptom brake juddering), so needed replacing but the pads were OK. I had them both changed anyway but argued unsucessfuly that the discs must be faulty if they wore out before the pads !

[madgeezer]

when u replace brake discs you must replace pads as well not the other way around. when you drive through sand gravel it gets picked up and lodged between the disc and pad making them warped.

blue discs = excessive braking under pressure

disc that look like vinyl record = stone/sand lodged inbetween

[BillyNoMates]

My experience of warped discs was poor manufacture. This was some years ago on a brand new Ford. They were replaced at the first service only to suffer the same problem - brake judder. Problem was solved by installing non-Ford discs. Warping can be caused by excessive heating of the disc but very unlikely as most are of the 'piggy-back' type i.e. 2 discs back to back with cooling vents in the middle. If manufacture is poor, the steel can have varying amounts of trace elements which can cause brake pull and in extreme cases warping.