997.1 C4S Rear brake discs CORROSION !

[Porschekit]

Hi All,

Thought I'd ask for some feedback on this;

Previously I had both front and rear discs, pads and accessories all changed at the same time with brand new parts.

After a period of time and on a recent minor oil service my local indy advised that the rear discs were 'heavily' corroded but "only on the inside surface of each disc" , yet the outside surface of each was shiny. Both fronts are fine and shiny.

He advised that this is common trait of the 997 model and that upon braking, the rear calipers trigger first and grip the disc setting the car forward momentarily and then the bulk of the work is done by the front brakes.

I thought it was a fault that the calliper wasn't pushing the pad on the insides, and therefore not gripping the inside of the rear discs, yet the outside of the disc is worn and shiny.

Anyone else have experience of this and is it a trait of the model?

deMort over to you .... :grin:

thanks all.... :thumb:

 

[C11BRA]

Hiya.

This is common on 996 & 997. & Boxsters I'm sure.

When I had my 996 the discs looked ok at first. Once I decided to keep it I overhauled them.

When I removed the discs the inside surface on all four was terribly corroded. I can only imagine that it is to do with the wishbone mounted brake ducts pushing road water/salt etc onto the inner face.

Never seen it so bad on other brands though. Quite odd.

DeMort. Over to you.

 

[benoniboksburg]

I think all cars brakiing is about 70% at the front.

 

[FZP]

Normal mate. Why it is, no idea. I changed in the summer with Brembo

 

[deMort]

Lol .. i like how its left to me

Yup it is normal and i've seen it since 2004 when i started working on porsches .. i'm not 100% sure as to why but Porsche brakes are a soft material that suffers more than other makes , far more water on the inside of a brake disc than the outside .

.. they are also better at braking efficiency because of this softer material ...

I think better brakes outways the risk of corrosion !

Image below of a forum members car and it can be typical of cars in general ..

if you live by the coast though then both sides will rust badley and pretty quick .


Only tip i can give which has been mentioned before .. if you wash the car then run it around the block to dry off the brakes ..

Failure to do this can result in the pads rusting to the disc .. this has a good chance of causing brake judder .


The image and its NOT an mot failure .. might not even get advised .. they get far worse than this .

 

[Porschekit]

Thanks for all the replies and to deMort for the extra detail :thumb:

You're spot on about the condition of the discs, see pics of mine attached;
I do live near the coast and I do dry the discs off after washing the car by dabbing the brakes on a short journey, but it looks like unless they get stood on pretty hard then the inside surfaces just don't get "wiped" often enough.

Equally when parking up in the garage at home after a wet run out they will also tend to corrode.

So at least I know it's a common problem and not just my car, thanks for the feedback chaps.. :thumb:

 

[biggriff]

Use Bilt Hamber Atom Mac when you've washed the car. Keeps brakes from corroding.

 

[Porschekit]

I had a look at the YouTube video and can see how it might work on the outside surface of the discs but can it be sprayed onto the inside surfaces easily, without being up on a lift or without some serious body contorting on the ground. Not sure all inside surfaces would be able to be coated?

 

[Jam911]

I had this a while back so I drove the car more and next MOT the corrosion had gone

 

[buttertubs]

noticed a bit more noise coming from my rear brakes so checked them and sure enough corroded on the inside face of the disc

There's no lip on the disc and plenty pf material left on the pads.

Is there anyway of cleaning them up or is it just a case of replacing them, or will they eventually clean up when i get to use the car more.

 

[The return of Marty Wild]

@ PorscheKit - I should say those discs need chucking in the bin. All the 'drill outs' have filled up with crud. I've heard of people drilling out the crap to service the discs, so that could be another option.

I did my brakes on the 986 this weekend, they were in a terrible state. Again with the hidden faces being worse. For some reason the associated pads had worn more quickly, down so much that I wondered if that side was getting any force pushed against it. And if not, that would be why the surfaces weren't getting 'cleaned' by braking forces?! :?:

Alas, on all my cars the brakes have been in a state until I've replaced them. Then they stay in much better shape after that. Which I have put down to giving them some welly regularly.

For the record, I don't drive the car after a wash and I'm yet to own a garage (sadly). Always thought moving the car before it's perfectly dry encourages crap to reattach itself to any remaining water, thus killing off your good work.

 

[The return of Marty Wild]

Is there anyway of cleaning them up or is it just a case of replacing them, or will they eventually clean up when i get to use the car more.

Really depends how set in the corrosion is. Sometimes they can be cleaned off to a perfect finish from what looks like a bad state. Just with a good drive and some heavy braking.

Or as said, if it's taken a hold, it's there until you replace the kit IMO.

 

[buttertubs]

Is there anyway of cleaning them up or is it just a case of replacing them, or will they eventually clean up when i get to use the car more.

Really depends how set in the corrosion is. Sometimes they can be cleaned off to a perfect finish from what looks like a bad state. Just with a good drive and some heavy braking.

Or as said, if it's taken a hold, it's there until you replace the kit IMO.

This is mine.

What do you think, will they clean up with an Italian brake tune or should I just replace them

Just to add the pads have loads of material on them.

 

[The return of Marty Wild]

I personally don't see them coming back from that, but I must confess, I am no expert.

Plenty of pad on both sides? I had the wear warning come up on dash on a wet wet wet TrackDay, visually inspected the brakes and the on show pads had loads left. Little did I know it was the hidden pads that had thrown the warning, I thought we had just melted a sensor or two. Although I did think that strange on a wet November TD.

Discs aren't expensive or particularly hard to change, I have done my R32 then Cayman and now Boxster. The improved braking is night and day, but then I am using way more braking surface area. Will be interesting to see if I can keep the pads/discs in better condition from using the car how Ferdinand would have wanted.

Also for the record, I don't drive my 986 in the winter but it did weather the last two outside. Which I plan to rectify going forward.

 

[buttertubs]

I personally don't see them coming back from that, but I must confess, I am no expert.

Plenty of pad on both sides? I had the wear warning come up on dash on a wet wet wet TrackDay, visually inspected the brakes and the on show pads had loads left. Little did I know it was the hidden pads that had thrown the warning, I thought we had just melted a sensor or two. Although I did think that strange on a wet November TD.

Discs aren't expensive or particularly hard to change, I have done my R32 then Cayman and now Boxster. The improved braking is night and day, but then I am using way more braking surface area. Will be interesting to see if I can keep the pads/discs in better condition from using the car how Ferdinand would have wanted.

Also for the record, I don't drive my 986 in the winter but it did weather the last two outside. Which I plan to rectify going forward.

yeah loads of material on the pads, they are almost like new.

I'll probably just change discs and pads for new

I've not spent anything on it for a couple of months so why not