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YOUR RESEARCHBrake Rotors
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I agree a cross drilled rotor will potentially need to be replaced before the end of its life from possible heat cracks but even Porsche has said that a drilled rotor provided a 30 degree temp drop at the rotor.
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I replaced porsche rotors on my GT3 with 16000 miles ( I tracked it couple of times and previous owners seemed to have) and cracks had started from the holes and started growing.
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I use Castrol GT brake fluid because its the highest boiling point of any reasonably priced dot3/dot4 fluid.
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I prefer slotted rotors, which I use on my e36 M3 for track driving, but for 996 C4S, Sebro seems to be the only one making one at reasonable price.
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As for pads I have used Pagids, PFC and Carbotech.
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Replace before the end of its life
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I agree a cross drilled rotor will potentially need to be replaced before the end of its life from possible heat cracks but even Porsche has said that a drilled rotor provided a 30 degree temp drop at the rotor.
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I replaced porsche rotors on my GT3 with 16000 miles ( I tracked it couple of times and previous owners seemed to have) and cracks had started from the holes and started growing.
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Suggestion
I probably should have been more specific, but Im only talking about low-end (like I would buy) machined cast steel rotors, not top shelf carbon fiber impregnated blah blah blah $10,000 a set rotors.
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Guys I need to replace the rotors on my 996-4S, the intended use for the car is street driving and some DE days. I have been reading many threads here in reference to brakes in general, and it seems there are many opinions in reference to brake pads and rotors.
While not 100% on top of it, I can see and understand the need for a different pad material depending on its intended use, track, DE, street, etc.
What I am a bit confused on, is the differences on rotors, I know drilled vs slotted, and ceramic vs steel, but even between the same type there is a huge difference on price for what, to me, seem to be the same consumable piece of steel. Am I missing something? I mean I figure after a few track days any brand rotor will crack and would need to be replaced, so why spend additional money on this part?
BTW, I am considering Cool Carbon pads and WBR Rotors, these rotors are $58 each and are drilled. What do you guys think.
https://shop.advanceautoparts.com/p/...921%7CL2*16462
It's hard to go wrong with OEM Porsche or Zimmerman E coat rotors (which are the same thing but less expensive at pelican parts) The factory stuff is pretty awesome and swapping out the pads for a DE event is really easy.
My advice would be to buy the cheapest rotor you can find from a brand you have heard of. It's just a piece of metal; a piece that says "Porsche" or "Brembo" on it is going to do the same job as a piece that says "Meyle" or "Ate" on it. All that matters is that it's made of quality, homogeneous metal and is machined to good tolerances, so it starts true and stays true. A non-brand eBay buy might not satisfy that requirement, but any name-brand aftermarket supplier you've heard of will be just fine, so don't waste your money thinking the more expensive part must be better for some reason! I've done numerous track days on cheap-o Meyle rotors with 0 issues. If you can find a brand-name rotor that's in that price neighborhood but is not cross-drilled, can you let the group know? Cross-drilling is kind of a waste and just eats pads faster and provides a place for cracks to start, as you mentioned. But at the price of those rotors and OE pads it's hard to get too upset about it.
I have used partsgeek for my brake rotors. Not knowing what year your car is I just plugged in a 2003 4S.
https://www.partsgeek.com/catalog/20...ake_rotor.html
Ate and Sebro are good rotors. I have slotted or cross drilled whatever your flavor. I've bought uncoated rotors and get a can of zinc rich primer and spray the rotor hats inside and out. As for pads I have used Pagids, PFC and Carbotech. The more aggressive the pad the motor rotor usage you'll see. For street pads I some inexpensive pads that I change out. Also it seems partsgeek's inventory changes and you can find some very good buys every once in a while.
If you are just starting out with DE's just go with your street pads and learn from there.
I suggest avoiding the crossdrilled, which is a misnomer anyway, they are not drilled, they are cast with the holes. Drilling all those holes would make them very expensive. The holes are known to cause cracking. While not on a 911, I have personally seen rotors cracked, and the cracks always start at a hole. The slotted rotors increase elimination of the gases that build up at extreme temps between pad and rotor without sacrificing structural integrity of through holes. I replaced mine when the original warped with slotted ones from Pelican, and have done several DEs with them.
The most recent DE, my car actually did back-to-back sessions with me driving one class and my Daughter driving another class. With temps in the mid 90s, we finally boiled the brake fluid on the second day, but otherwise they held up nicely. I use Castrol GT brake fluid because its the highest boiling point of any reasonably priced dot3/dot4 fluid. Yes, you can get higher BP, but the price goes outa sight for those.
The suggestion to change out pads for DE versus street usage is a very good one, but I would suggest marking the pads so you put the same pad back in the same location it came out of. I believe this will reduce hotspots caused by variations in facing, IOW a pad may be touching the rotor in only one area versus more distributed across the face of the pad/rotor once its seated.
Last, I suggest looking at the GT2/GT3 cooling ducts which can be added to the non-GTx cars very inexpensively. Here is the more expensive version:
https://www.suncoastparts.com/produc...634111890.html
and here is a cheaper version
https://www.suncoastparts.com/product/PKGT3FRS.html
both are EOM Porsche parts.
I'd like to hear more proof about holes causing cracking. Would Porsche and others continue to use rotors with holes if they were weaker? I get it that a knock-off cheap rotor with holes is not the way to go, but OEM? And Porsche OEM? A company that prides itself on selling race-ready street cars?
Are the upgrades/premium brakes on high end performance cars more often cast with holes or solid?
I'm really just asking, not telling anyone. I'd like to see hard evidence here. Scientific. And as for those cracked rotors that started at the holes, maybe those rotors were well worn and being operated at or beyond their minimum thickness standards?
Has anyone tested these things? (I would assume the manufacturers have.)
I don't have the science behind it but it absolutely happens. Cracks form at the holes and begin propagating toward other holes and toward the edge of the rotor. Typically if these rotors are run hard, they will need to be replaced for cracks before they will reach their minimum wear thickness. Once the cracks connect adjacent holes, or extend all the way to the edge of the rotor, it's considered a risk to keep driving on them. It's not an issue that shows up in street driving, but definitely will on track.
I replaced porsche rotors on my GT3 with 16000 miles ( I tracked it couple of times and previous owners seemed to have) and cracks had started from the holes and started growing. As stated, it is a well-known issue and so long as they are replaced before cracks connect holes or reach the outer edge of the rotor, risk is minimal. I prefer slotted rotors, which I use on my e36 M3 for track driving, but for 996 C4S, Sebro seems to be the only one making one at reasonable price.
When Porsche came out with the 991 they went to cast hole rather than drilled. The rotors are lasting longer but are still JUNK. Real race cars have 2 piece slotted rotors like AP, Giro Disc or PFC. If you are tracking your car in the long run the 2 piece is the most economical if you are running a newer car. Some of the older cars like 944s have pretty cheap OEM rotors.
Porsche could go to a slotted rotor.....but then they would lose out on all the money they make replacing the OEM drilled/cast rotors.
Are those even steel rotors? I probably should have been more specific, but Im only talking about low-end (like I would buy) machined cast steel rotors, not top shelf carbon fiber impregnated blah blah blah $10,000 a set rotors. That car looks to be a GTx or cup car, and the mechanic is torquing the 400ftlb center lug. I probably cannot even afford that torque wrench.
Those are definitely still iron rotors. I agree a cross drilled rotor will potentially need to be replaced before the end of its life from possible heat cracks but even Porsche has said that a drilled rotor provided a 30 degree temp drop at the rotor.
When I was 16, back in 1979/1980, I was at the local British car dealership (they may have had a Porsche and Mercedes dealership too) on route 17 in NJ getting parts for my MGB. I remember there was a huge disk brake rotor on the counter that was cross drilled. The steel was all the colors of the rainbow and all if the holes were connected with little cracks. I remember thinking how beautiful it was, in a way engineers can appreciate. I asked them what car it came off of and they said "a Porsche 917".
I just ordered a set of rotors from Advanced Auto pars, thing is we couldn't figure out if they are cross drilled or not. They have two part numbers as expected, one for the right the other from the left, but when looking at the picture for each part, one shows cross drilled the other one slotted, so it will be a surprise when they arrive. If they are different I will just return them to the store for a full credit. If they are not coated, I will pain them with a zinc primer.
They had a cost of $69 each, but Advance had a coupon of 20% off, so they came out to be $55 each, not a bad deal, considering.
I will report back when they arrive.
