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Yes, welcome to SCCA where an otherwise stock Porsche with slotted rotors instead of the factory crack-prone cross-drilled ones will put you in Street Prepared.
This has always been my gripe with SCCA. If you have a Chevy you can run Street, street touring, or CAM on street tires. Or you can hop into SP if you want to dive full-on into race tires.
If you have a Porsche, with very rare exception like the STR-legal 944s or air-cooleds, changing brake rotors means you're in SP. Keep in mind that SP allows deleting the AC and sound system, balancing the rotating parts of the engine, removing the air filter, fender flares, unlimited wheel size, etc. There's no middle ground for us. And that's fine since our cars are pretty great in Street-legal form but still. Every time I think about doing MCS coil-overs I just read the SP rulebook and know I don't want to go down that road and ruin my car.
I'd like to add the caveat that at anything but a national event nobody is going to care if you run slotted instead of drilled rotors. At most National events nobody is going to care. If you happen to beat someone and take their contingency, and they're a total dick, only then would it be a problem.
The intent of the rule is to protect from people swiss cheesing rotors to save weight. Yes, people do it when allowed to:
I saw one of the prepared cars had cut his into like a cog shape on his windshield-less S2000. Crazy. And I get that no one wants me to swiss cheese rotors on my Street Class car...but come on I can't even put off-the-shelf slotted rotors on?
And I agree; no one is going to protest anyone for slotted rotors or anything like that. But it's annoying that you're relying on that and no one wants to feel like they are "cheating."
I'd like to add the caveat that at anything but a national event nobody is going to care if you run slotted instead of drilled rotors. At most National events nobody is going to care. If you happen to beat someone and take their contingency, and they're a total dick, only then would it be a problem.
The intent of the rule is to protect from people swiss cheesing rotors to save weight. Yes, people do it when allowed to:
Weight savings has gone too far when competitors remove their wheels and tires to shave unsprung rotating mass. Keep it sane, people!
+1 for locally nobody will care. But, technically, it's not permitted.
The Street Touring allowance already sort of addresses the swiss-cheese thing by saying the voids comprise no more than 10% of the braking surface area. Here's a first stab draft at a rule that allows people whose car came with vented rotors to run whatever type of vented rotor they want, or even a solid rotor if maybe they never track the car and wanted to save some money. It could be drafted in a way to allow people with solid, non-vented rotors to upgrade to vented, but I think that creates work for people in the slower Street classes in that now they would feel like they had to go out and buy vented to save a few ounces and remain competitive. I also don't want this to turn into some sort rotor-weighing or thickness-mic'ing impound extravaganza. That being said no one should be running their rotors below minimum thickness spec regardless, for safety sake. I also don't want to unnecessarily add rules to the rulebook, but at the same time I think a lot of cars come equipped with cross-drilled because the public thinks they look cool, and then we start driving them hard and crack them way before they run out of usable depth.
"Cars originally equipped with vented brake rotors may use non-standard brake rotors provided they are of equal dimensions (diameter and thickness), made of the same material, and assembled using the same number of components as original equipment (i.e. 2-piece rotors and/or ceramic rotors are allowed only on cars originally equipped with such). Thickness includes the individual plates of a vented rotor, as well as the overall dimension. The diameter for replacement rotors is measured at the minimum outside dimension. Overall rotor thickness may not be below the manufacturer-recommend rotor replacement criteria. Each rotor must weigh at least 90% of the weight of the original equipment rotor it replaces."
That rule would open up a prep allowance that, if Street Touring is any indication, a non-trivial number of people would take advantage of for the ~2 lb. of rotating, unsprung weight savings per corner.
Note also that the 90% weight rule would be tough to adhere to and tough to enforce. Tough to adhere to since brake manufacturers typically don't publish rotor weights, so you'd have to buy rotors and measure them yourself. Tough to enforce since, to ensure compliance, you'd need to acquire an OEM rotor, turn it down to minimum thickness (thus rendering it non-returnable), and weigh it.
Is this cost and new allowance justified by the convenience of being able to run aftermarket slotted or drilled brake rotors on a car that didn't come with them stock? Seems to me that the status quo (technically illegal but no one will care locally) is good enough.
Last edited by PedalFaster; 03-27-2018 at 03:30 PM.
I once had a set of aftermarket replacement front rotors that had little cuts in them. They were curved, routed slots that didn't go all the way thru. Not sure how I ended up with them, probably an ordering mistake. At that time it didn't occur to me that they were illegal.
I went to one of the very first Match Tours with them on the car. Someone in my class complained to everyone who would listen, in and out of the class, except not to me. I know this because they all came to me and said this guy was very upset and thinking about protesting me. Several people told him he was nuts, which only made him madder.
I apologized to him and told him that I would withdraw if he wanted me to. Luckily, he didn't insist.
I tend to agree with Pedal Faster that it's dumb to try to write a rule for every little thing and then enforce it. But then you have stories like ed's that make you shake your head. I think one of the AS C5 corvette guys was telling me someone gave him **** about his stubby antenna on his C5 corvette, and it not being comfort&convenience since it had less drag than the stock radio antenna.
That rule would open up a prep allowance that, if Street Touring is any indication, a non-trivial number of people would take advantage of for the ~2 lb. of rotating, unsprung weight savings per corner.
Note also that the 90% weight rule would be tough to adhere to and tough to enforce. Tough to adhere to since brake manufacturers typically don't publish rotor weights, so you'd have to buy rotors and measure them yourself. Tough to enforce since, to ensure compliance, you'd need to acquire an OEM rotor, turn it down to minimum thickness (thus rendering it non-returnable), and weigh it.
Is this cost and new allowance justified by the convenience of being able to run aftermarket slotted or drilled brake rotors on a car that didn't come with them stock? Seems to me that the status quo (technically illegal but no one will care locally) is good enough.
Even if this allowance becomes a de-facto requirement due to weight savings, it still seems well within the philosophy of the class. I mean, if you can replace your crummy non-adjustable dampers with trick double-adjustables and custom bump stops because they're "wear items", brake rotors seem aligned with that, too.
03-22-2018, 07:08 AM
Slotted Rotors ?
