Need Help With Porche Brakes

[timsr33]

ive bought a set of porshe 996 carera cup calipers and 350 mil rotors as that is the abolute biggest brakes i can fit under the standard r33gtr rim

what i was wondering is how much clearance around the rotors do you need for the rotors to still get good cooling or is clearance not a big issue

the clearance ive got 25 mill right around the rotors and about 5 mill clearance around the caliper is this enough

thanks tim

[dazmo]

That set up will be fine mate. If you are concerned about air flow make up some ducting to run to the rotors this is recomened regardless of how much clearance you have anyway.

[timsr33]

im going to run ducting the main reason im asking is every one says you need 18s for the porsch 6 piston brakes but ive got them to fit under the 17s its a tight fit but they fit so i thought there must be another reason they say you need 18s and the only thing i could think of was cooling of the rotors thanks tim

[Risking]

I thought 996 cup cars had the smaller caliper which does fit under a 17. I have a GTR here at the moment with them and 17's

350mm rotors are not that big and you should be able to run a 17 without much trouble.

I use the 997 cup car caliper (the big 6 spot) with a 390mm floating rotor and not many 18's even fit over them.

We've found with more rim clearance rotor temp does drop significantly.

The example I can provide was from my old F50 brembo's with 355mm rotors

17's with approx 5-6mm caliper to rim clearance 15 laps of wakefield rotor temp was 680 degrees.

18's with un measured clearance but clearly more, same driver and laps 1 hour latter. 540degree rotor surface temp.

All laps were within .8second (1:05 sec laps)

[timsr33]

they must be 997 calipers then they are the big 6 pot ones

the rotors were 365s but i machined them down to 350 to clear the rims i think ill try them and see how they go and if all else fails ill get some 18 by 10s

thanks for the advice risking

[Risking]

This is a 997 cup car calliper

It has the longer more rounded end on it compared to the 996. Post up a photo of the caliper and Ill be able to tell you which model it is.

The pads are different as well. The 997 cup pad is massive, the 996 is not as big.

There is other 997 turbo brakes around as well which have smaller rotors so perhaps your are from that variety.

The 997 cup cars use 380mm floating rotors so 365's would not be cup rotors.

[Owgasm]

interesting.. i got minimal clearance.. but completely different brakes.

can't even fit them under my 18 enkeis had to modify the rims a bit.

Edited June 9, 2009 by Owgasm

[sav man]

This is a 997 cup car calliper

It has the longer more rounded end on it compared to the 996. Post up a photo of the caliper and Ill be able to tell you which model it is.

The pads are different as well. The 997 cup pad is massive, the 996 is not as big.

There is other 997 turbo brakes around as well which have smaller rotors so perhaps your are from that variety.

The 997 cup cars use 380mm floating rotors so 365's would not be cup rotors.

pretty sure that's a 996 caliper. i've got them on my car (355mm and won't fit under r33 17's), they have a huuge pad, bloody expensive to replace.

[timsr33]

its these calipers but not the rotors

[Risking]

Those 100% came from a 997 cup car.

As far as I was aware the 996 and 997 cup cars had slightly different calipers. I know when I tried to put mine over a 355mm brembo rotor the pad did not contact the entire radius so I bought the matching cup rotors straight off the 997 the calipers came from.

Those in your photo are different to mine. The mounting points in mine are at the very very end of the caliper and dont have the raised lugs.

They are 996 cup car calipers. They are indentical to the 996 cup ones I have sitting here.

John at unique had a set of those on his Z and upgraded to the 997 as well.

Edited June 9, 2009 by Risking

[timsr33]

i didnt even think of the pad contact when i machined them down and wont no if they will work untill i acctually buy pads and get my car back from the bead blaster thanks for the help risking

[Risking]

Buying pads is the expensive part.

If you find a few people running the 996 cup cars you can actually buy their second hand pads pretty cheaply to get you going.

The pagids for a 997 are around the 1K mark for a set of fronts.

Obviously a few people are using the 996 or 997 with a 355mm rotor so you should be okay.

[timsr33]

how are the pagids ive been told the ds3000 are the way to go and i got quoted 700 for the ds3000s but second hand ones could be good to thanks again

[R31Nismoid]

That set up will be fine mate. If you are concerned about air flow make up some ducting to run to the rotors this is recomened regardless of how much clearance you have anyway.

with ducting, whats always made me wonder is the temp difference

the inside of the rotor would be cooler than the outside.

I remember Troy (Roy) saying something about this in one of his drunken late night posts in the brakes area but i dont remember there actually being any evidence for/against if there is actually problem with uneven temps that would no doubt occur

[Owgasm]

ineresting point nismoid.. i've got some ducting for the rears..

Diffferent temperatures would possibly cause the rotors to bend.. cooler on one side hot on the other...

[Risking]

The idea of the internal veins is to distribute the heat and channel air through the rotors surface.

I find the pagids to be very good even if I do use the second hand ones. Ive had surface temps of 850 degrees and the pads do start to break up but they are yet to fade. I have not had any pad fail or crumble as yet.

Ferodo and pagid are the only ones Ive used, pagid is better but more expensive.

Main thing I noticed was the pedal feel after 20mins of driving hard. The pagid was fine the ferodo had started to fall away.

Edited June 9, 2009 by Risking

[sav man]

I can see the diferences now side by side. The 997 pads must be fricking huge, cause the 996 ones are bloody big. I've had pagits (RS14), and hawks. I prefur the Hawks (HT10), the pagits brake up when they get low, havn't had that problem with the Hawks. I think i payed $850 for the hawks

[Risking]

Yeah the 997 has monsterous pads. Maybe 15% more than the 996.

I actually have both pads here, ill take a photo and post it up latter

[Merli]

with ducting, whats always made me wonder is the temp difference

the inside of the rotor would be cooler than the outside.

That's why you should ALWAYS point the ducting to the inside CENTRE of the rotor.... The air will go through the vanes inside the rotor to cool both sides of the disc.

Those setups that you see where the ducting points directly at the rotor face is far from ideal.

[timsr33]

thanks for the help fellows i think ill just use them and see how they go its good to no i got bigger calipers then i thought yippy