On my car I have had a couple of sets of pads but not any disks yet. Car had done 30K, but I have not measured the disk thickness yet. Pads were changed because a)) Fastfit fitted new pads when only the sensor wire was broken b) Fastfit pads caused sqeaking so OEM pads were fitted again.
IIRC correctly the OEM data shows the new disc to be 12mm and be replaced at 10mm
On this basis when should the discs be replaced (i.e if new pads are put in when the discs are 10mm then the disk will wear below the 10mm limit)
Is just working on the basis of 11mm or more is ok (the disks only have a 2mm wear across their life)
What do others do?
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Discs should be replaced at 10mm if that is the specified limit. Pads must be changed at the same time as new discs are fitted.
It makes little sense to fit new pads then change them again if the discs need changing soon after, so it's sometimes better to change the discs a bit early.
Not knowing how the car has been used, how old it is, or what make/model it is difficult to comment on how likely the discs are to need replacing soon. When you do take a measurement, you should be able to estimate how much longer they are likely to last.
hth,
Andy
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I think original disks with makers pads will last quite a long time unless the brakes aren't used much (and rust).
Once you've changed to third party disks and pads then wear seems to be much faster. IMHO
Martin
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Just to add to the advice above, I think the decision to change discs may depend on whether they are scored or otherwise worn unevenly. If they still appear smooth and shiny I would not worry about letting them go 1mm beyond the spec.limit.
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As Andy says, it all depends on the make/model. On previous Vauxhalls of mine, the suggestion was once the discs have worn down to "x" mm, then do one more pad change and then replace both the pads and discs when those pads have worn. You'll find as your discs get thinner, the pads will be eaten up quicker anyway. Well it was in the case of my old Astra and a couple of Cavaliers. The brakes got that bit hotter as there was less metal to dissipate the heat and things wore progressively quicker.
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The original disks on my Volvo have done 304,000 miles, still unmarked and well within specification. The pads (always non-asbestos, before anyone asks) do about 50,000 miles.
You people sure must do a lot of braking!
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I replaced my girlfriends 206 discs and pads at 35000 miles because the discs were below limits, even though the original pads were OK. Perhaps discs are made to wear out quickly as it is a nice little earner replacing both discs and pads (or am I being paranoid!!)
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I had to change the rear discs on my 405 at 100K miles.
This wasnt through wear, They where still in spec, But they started to crack up!
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It is normal for both discs and pads to wear. With the use of asbestos free pads, disc wear is higher than it used to be. Expect to have to change discs every second or third pad change. Discs should be changed before they reach their xmm wear limit, or if they are badly scored or suffer from excessive runout (uneven wear which can be measured and has a manufacturers limit).
Pads should be always be changed at the same time as the discs and also as a complete axle set.
It is a false economy not to change discs when they are worn as pads will wear much quicker (and unevenly) with worn discs. The pads also take ages to bed in!
Recently, on my Golf Mk 3 I only got 15,000 miles on a set of pads with worn discs. With new disks, pads last more than twice that mileage.
Discs are cheap and simple to replace, so do it! Brakes can save your life!
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I immediately checked the disks when I recently bought a Mondeo II. The one thing I did notice was the surprising amount of rust blocking the ventilation slots. It took some while, using various screwdrivers, to clean out and chip off the majority of it. There was a significant pile of debris when I had finished.
I have not seen any mention of this aspect of checking discs.
I guess it is possible that discs can rust from the slots outwards and this would fool any thickness check.
With vents blocked the heat dissipation must be be reduced but by how much?
I would suggest that checking / clearing the vents is included in the regular checks.
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Discs are made of cast iron (?) and will accumulate rust (scale) on unswept areas. It builds up especially on the rims, where it commonly makes the pads hard to remove. I chip the rims back to metal once a year, if I remember to.
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