Hey guys, would be grateful for your thoughts and expertise on something.

My 996 GT3 has the typical hairline cracks from the holes in the front discs. They are about 7-8mm in places, and I know Porsche say change them out at 5mm. Discs and pads have plenty of life otherwise and car doesn't get tracked much but does get driven quite hard.

I know they don't cost a fortune, but I'm not in the habit of wasting money! Should I replace them?

Cheers,

Tommy

 

I would advise to leave them on for now. Once you get a significant number of cracks measuring more than 10mm, then you can replace them. You can never punish them as much on the street as they are designed to put up with on the track.

I recommend replacing them with the Brembo 2-piece slotted rotors. They are about twice as expensive, but last around 3 times as long.

 

Thanks very much.

 

Sorry I have to disagree with this. Do you want to take the chance that your rotor might explode and do some serious damage to the corner of the car? I have seen it and it's not pretty. Besides that, foremost it's a safety issue. Even if you don't track the car, high speed street driving still produces plenty of heat which will accelerate the already existing cracks.

I track my car and went with the Girodiscs. High quality and a reasonable price compared to the Brembos, although they are also a great rotor.

 

I have a set of Giro's coming in, good to hear you are happy with them.

 

+1 as well. Two things I never compromise on any of my cars - tires and brakes. These are what keep you on the road.

Slotted Giro discs are the way to go in my opinion. I love mine.

 

Thanks for your thoughts. I guess my question is, is the 5mm limit a sensible one or is it Porsche BS? They crack very readily. I agree that comprimising safety is a no no, but just assessing the risk.

 

I've heard to only worry when the cracks from one holes meets that of another.

No idea if this is accurate. Just passing it on.

 

I think I remember the Porsche memo that said 7mm cracks, joining cracks between holes, or cracks going to the outer edge. Anyway you are close and should order something now. I personally don't think Porsche is BS-ing on this one.

 

I have 4 track days on my Girodiscs, very happy with them. They haul me down from 150mph with ease. A friend of mine is an instructor and he rode with me for one session and was commenting on how incredible my brakes work considering the weight and speed of the car. I do have the GT3 6 piston upgrade and 350mm discs, coupled with SRF, Pagid yellows front, and Pagid blacks rear. I highly recommend this combo.

 

see attached

my advice:

hole to hole cracks -- replace
cracks to the edge of the disc -- replace

otherwise not

(I am not a lawyer or an engineer so at your own risk etc )

these are smaller than I wanted but should still work

 

Hey PJS, is that a picture of the Girodisc? I have always used discs with holes and replace them when the cracks are about 7-8mm...how do you know when to replace them if they don't have holes where cracks form?

 

thickness and cracks to the edges I believe

those are brembo type III 380 mm fronts in the pic

giro disc does not make a 380 mm replacement yet... yet

I am told they are in the works

I would have bought the gd if they were available

 

While it's tough to give a solid answer as to whether or not to replace or keep the rotors without physically seeing them, I can only reference the official Porsche protocol:

There is no need to remove cast-iron brake discs if the perforation crack lenght is less than 5 mm.
Maximum permitted perforation cracks are 5 mm.

Once again, this is the Porsche Service wear assessment protocol. I personally wouldn't want to risk an accident running overdue rotors, especially when you say you drive it quite hard, then again I've learned my lessons regarding car maintenance the hard way.

 

yes - see PDF attachment in post 11
that is Porsche documentation