I,m taking my car in for sevice next week, with 12k service intervals in mind, at what size should the garage change my brake pads?
also, how thick should the discs be before changing.
The garage has said that alot of cars now need new pads at 24k and are regularily fitting discs at anything from 36k onwards.
Any help is greafully recieved
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Hello
Sometimes garages change the discs every other pad change at the request of the customer obviosly.
With thanks
Martin G Winters
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Hi,
As a technician, there are things you need to know about your car. A lot of modern cars have a brake pad warning sensor to tell you when the pad is worn to its safe limit. Consult your dealer to establish if yours has. If it does then your on dash warning light will tell you when its time to change them. Its a simple process of a wire bonded into the pad during manufacture. When the pad wears down to the wire it exposes it making an earth via the disc and hey presto your dash warning light comes on. You generally have a couple of thousand miles left to get them changed. As for the discs, my opinion is that if you are going to get the car serviced as per the makers instructions then the Dealer will advise you if they have worn to the minimum thickness. Discs can last 100k depending on how the vehicle is used- excessive high speed braking tends to seriously reduce disc life.
Hope this helps
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These are the views of Robin the Technician with 35 years in the trade. I fix, therefore I am...
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Flatfour, the general rule is to change the pads when one of the four gets below 3mm.
I would also advise against having blind faith in any pad wear indicator system (if fitted) especially in an older car.
As for the discs, they could be physically marked with the minimum thickness or it might be mentioned in the driver's handbook. Failing that you could always ask to see the relevant page in the workshop manual!
As has been mentioned many times before, since the introduction of non-asbestos pads, discs are now a service item.
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As CMark says, there are 4 pads on a front 'axle' set, and if any one of them gets less than 2mm thick, the whole lot should be renewed. Though I have driven cars with one pad about 0.02mm left (makes a foul noise). And yes, wear indicators are unreliable as the connecting wires easily get broken.
Solid brake disks with 10mm new are allowed by the manuals to go as far as 8mm before replacement, but again I have been told that things are fine at 7mm or even a bit less. May need to be a bit more careful with vented (sandwich) disks.
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I've always worked to the old 1/8 inch rule, which I suppose is about 2mm.
As to disks, I think it's down to quality of the metal and driving style.
I have 2 Volvo 240s: one was owned by a colleague who drove on the brakes and needed new disks at 130,000 miles. The disks on mine are still within tolerance at 285,000 miles.
I think garaging helps too. If the car dries out then the disks don't rust so much.
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I support the advice you have been given, but the key point is that you are expecting the garage to do the work as part of the service. Their decision process will be slightly different to a competent DIY'er. After all they must look at it from the perspective that they will not be seeing you for 12 months/12000 miles, so I believe they will change the pads out earlier or at the very least tell you to book the car back in 'x'miles for a pad swap. The risk of course if pad change is delayed (saving say £2 or £3 quids worth of pad material)to the point where metal to metal contact occurs is wrecking your discs and worst effective brake failure and a crash - particularly in the wet!
As to the discs themselves the tolerance is on thickness, run-out and surface finish. As has been mentioned the downside of asbestos free alternative pads is that they thrash the disc much more and quite often you may have to swap out the disc because of heavy ridging alone.
As ever with these things the parts are relatively cheap, it is when it is combined with dealer overheads to carry out this relatively simple task that the bill becomes unpalatable.
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