Corroded disks
Discussion
Ive got big reds on my 993 C4S - the ones with the floating disks. They looked fine to me and have about 12-15k wear, they are hardly worn on the outer surface. However Steve from Jaz called me this am to say they are completely corroded on the inside and must be changed - bigs chunks are missing.
The car is used regularly but apparently it is very common - anyone else had this problem with these brakes. At £150 a disk I could do with avoiding it in the future!
The car is used regularly but apparently it is very common - anyone else had this problem with these brakes. At £150 a disk I could do with avoiding it in the future!
'your discs are corroded sir' is a usual OPC money making scheme - nothing a hard brake from 100 wouldn't sort out through tbh for surface corrosion - especially on the rears.
BUT saying bits are 'missing' is a cause for concern - ask them to show you (you'll need to get under the car presumeably on a lift) and if bits are indeed missing - then be gratefull they picked it up..
Do you wash the car and then put it away immediately ? If used daily then this should not be an issue - but even leaving wet discs for say a week will eventually corrode them badly - they are Iron afterall ...
A skim 'may' resolve the problem - but IMO not worth the grief vs outlay especially on disc that have done 15K ish.
BUT saying bits are 'missing' is a cause for concern - ask them to show you (you'll need to get under the car presumeably on a lift) and if bits are indeed missing - then be gratefull they picked it up..
Do you wash the car and then put it away immediately ? If used daily then this should not be an issue - but even leaving wet discs for say a week will eventually corrode them badly - they are Iron afterall ...
A skim 'may' resolve the problem - but IMO not worth the grief vs outlay especially on disc that have done 15K ish.
I had the same on the rear discs of my 993 C4. I keep the car outdoors, I left it standing without driving for about two weeks in wet weather. When I came to drive it the pads were initially stuck to the discs. Next time the car was in for a service (Indy not OPC) I was advised there were chunks missing on the inside surface of the rear discs. I was very cynical as the outside of the discs was like new. I decided to change them myself and exactly as the mechanic had described there were large chunks missing from the inner surface.
What you have been told is all very plausible. As Manek says never forget to drive the car immediately after you have washed it and if you keep it outside make sure you drive it very regularly.
pp
What you have been told is all very plausible. As Manek says never forget to drive the car immediately after you have washed it and if you keep it outside make sure you drive it very regularly.
pp
believe it or not it really is very common to see discs very corroded on the inside, they are high iron content discs and do suffer from corrosion, no idea why they sometimes look ok on the outside, maybe is a cooling issue, however as an OPC tech we never unjustly change disc to make money, you are always given the choice and if you decide to drive you're high performance sports car away with rusty discs it is you're choice
wildoliver said:
I'd get them skimmed if I were you, had some 996 ones done a while ago (only c2) and very impressed. £15 the pair!
The only problem with skimming is that if chunks are coming away from the inside (and Steve at Jazz isn`t a bloke who tries it on to try and earn a fast buck), you risk going below the minimum thickness for the discs. Not sure how you paid £7.50 per disc, it would cost more than that to get the machine out of it`s cover or to get the discs off the car and onto a lathe !Discs are unlikely to fail totally (although it can happen), it`s more of an annoyance when you feel a judder, or a wobble under braking. Having just spent over £3,000 on my GT3 road car getting the front brakes sorted to my liking a couple of hundred quid to ensure all is well doesn`t seem out of the way.
James is a good man, he`ll do the right thing !
Henry
Well from an engineering point of view the depth of metal usually taken off a disk as a general skim is not enough to take a disk below limit for about 2-3 skims.....Depends on the disk obviously, but generally Porsche disks have quite a lot of meat on them, the amount needed to be taken off to take it down to a smooth surface underneath the chunks is not usually much more than they would take off anyway. But like most things it depends on the circumstance these may be quite horrific, however if the car is fairly regularly used I'd be surprised, that said I have no idea how much meat is on the floating disks.
As for price £15 for an engineering company to lathe them down is not excessively cheap, cash deal done during lunch time on a lathe that is used all day every day anyway, just pick the right company to start with, small family companies are always looking for work however small.
As for price £15 for an engineering company to lathe them down is not excessively cheap, cash deal done during lunch time on a lathe that is used all day every day anyway, just pick the right company to start with, small family companies are always looking for work however small.
Remember with skimmed discs you should use new pads with them and they should be treated as new discs as far as running in is concerned. ie both surfaces (pad & disc) are flat as opposed to just re-using the old pads with 'new' discs = re-grooving the new discs with the pattern on the worn pads (usually the edges) = much less brake efficiency well past the normal 'new' running in peroid.
So it may well be only £15 per axle but you should be adding the cost of new pads as well (you'd need these anyway on brand new discs.. ) but just to add to the debate on skimmed discs ...
Richard.
So it may well be only £15 per axle but you should be adding the cost of new pads as well (you'd need these anyway on brand new discs.. ) but just to add to the debate on skimmed discs ...
Richard.
Had my discs skimmed but this was done with the discs in place on the car with a specially designed machine for the process. Was around £80 for the pair of rear discs to be done, took about 30 mins in total including removing and refitting the rear wheels. I've done about 15k miles since the second skimming.
Silver993tt said:
Had my discs skimmed but this was done with the discs in place on the car with a specially designed machine for the process. Was around £80 for the pair of rear discs to be done, took about 30 mins in total including removing and refitting the rear wheels. I've done about 15k miles since the second skimming.
Not sure that you can have floating disks skimmed on the car!dilbert said:
Silver993tt said:
Had my discs skimmed but this was done with the discs in place on the car with a specially designed machine for the process. Was around £80 for the pair of rear discs to be done, took about 30 mins in total including removing and refitting the rear wheels. I've done about 15k miles since the second skimming.
Not sure that you can have floating disks skimmed on the car!
wildoliver said:
As for price £15 for an engineering company to lathe them down is not excessively cheap, cash deal done during lunch time on a lathe that is used all day every day anyway, just pick the right company to start with, small family companies are always looking for work however small.
Right, so that was just to put the discs on a lathe, you still had to get them off the car, take them to a friendly engineering company, badger someone to do the job (probably a case of leave them with us & we`ll see what we can do), go back and collect them later / the next day & re-fit. The quoted figure of 80 pounds to do the discs in situ is more realistic.I only post this as some people will read the original post and assume 15 pounds is a typical figure to get discs skimmed, all in.
Henry
Gaity said:
Can somebody explain (simply) 'floating discs', please? I replaced my 993C4S discs a while back and didn't notice anything different to other discs (on different vehicles) I have replaced in the past.
Trev
I have a feeling that my idea of floating discs is different from other peoples. TBH I don't think you should feel confused.Trev
wildoliver said:
Yes when you look at it that way Henry your not far off right, I tend to take for advantage the fact we work on our own cars so removing the disks etc. Costs us nothing.
If you're in the business surely it does cost you since you could be working on a customers car during that time, so you're losing revenue & profit.One other thing.
New disc pads on the rear of a GT3 cost more that the discs themselves, so on a very high performance car thatis intended to be used at reasonably close to it's very high limits, the relative value of skimming runs lower and lower down the scale of options.
One other thing to beware of. I have just bought a GT3RS which is booked in for a full new set of brakes. The previous owner had experience heavy fade and asked a track day dealer to fit harder pads for him. These totally destroyed the discs. That was an expensive trackday (the brakes being priced into my purchase).
(Also, why give an insurance company anything to argue over in the unlikely even of a claim. You know they make their money from not paying out (this maybe a slight exaggeration to illustrate a point !)).
New disc pads on the rear of a GT3 cost more that the discs themselves, so on a very high performance car thatis intended to be used at reasonably close to it's very high limits, the relative value of skimming runs lower and lower down the scale of options.
One other thing to beware of. I have just bought a GT3RS which is booked in for a full new set of brakes. The previous owner had experience heavy fade and asked a track day dealer to fit harder pads for him. These totally destroyed the discs. That was an expensive trackday (the brakes being priced into my purchase).
(Also, why give an insurance company anything to argue over in the unlikely even of a claim. You know they make their money from not paying out (this maybe a slight exaggeration to illustrate a point !)).
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