Anyone drilled rotors for better braking?

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It really doesn't do anything for a street car. Best bet is to get better pads.

On a side note.... You can't turn drilled rotors (or you will have a very hard time finding a place that will).


If you are having problems stopping an A-body with 12" rotors you have other problems.

This is an example....

http://www.hawkperformance.com/performance/


Just like it is bad to over cam your engine you don't want to over brake pad your car.

Don't be tempted by a "Track" pad. Pads for the track need a given heat level to work well. A heat level you may not see on the street.

Track pads "can" work like crap on the street when cold.
 
1968FormulaS340 said:
It really doesn't do anything for a street car. Best bet is to get better pads.

On a side note.... You can't turn drilled rotors (or you will have a very hard time finding a place that will).


If you are having problems stopping an A-body with 12" rotors you have other problems.
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he's right.....make sure your rear brakes are good and make sure they are adjusted up to proper specs.....allot of people miss the proper adjustment on rear brakes.....:-D
 
i was going to buy the 12" drilled slotted rotors as you can get them for pretty much the same money as stock rotors, but its stuck in my head that they cant be cut. i really have no use for a rotor that cant be cut for that kind of money. i dont know if its true or not but i heard valid points why you dont cut them. i just oredered a std set from advance auto.
 
jamesdart said:
i was going to buy the 12" drilled slotted rotors as you can get them for pretty much the same money as stock rotors, but its stuck in my head that they cant be cut. i really have no use for a rotor that cant be cut for that kind of money. i dont know if its true or not but i heard valid points why you dont cut them. i just oredered a std set from advance auto.
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I may be wrong but I think the biggest thing is the risk of damage to the cutting equipment.

Better to tell one customer "NO" than to tell 10 customers "We can't" because our machine is down.
 
I think you will find that if you drill the stock rotors you will get cracking from the holes. This would be a bad situation. I personally have no experience do that, but a machinist/roadracer that I know, tried it with bad results. I don't know what the difference is in metallurgy between an aftermarket drilled rotor and a stock rotor but I suspect there is.
 
As far as metallurgy goes, I would suspect that the aftermarket rotors get their hardening after the holes are drilled, and not before. Also, you'd have to chamfer the edges if you did it yourself to try and prevent cracking, if you skipped that step you'd definitely have cracking problems.

Drilled rotors do nothing to increase your stopping power under standard conditions. They lighten the rotor slightly and provide better cooling by allowing a better release of heat, so if you have problems with brake fade or warped rotors, they will help with that. But they won't increase the overall stopping power of the brake, they just keep it from going away as fast by keeping the brakes cooler. So if you're not overheating your brakes, ie, you've never had brake fade issues with your current system, you won't see much, if any, improvement.
 
some reasons i was told why you cant cut them, the edges wont be chamfered any more which will eat up the pads real quick, the rotors will be more likely to crack without being chamfered, and the slots can and most likely be different depths on each side after cutting so you will have unequal breaking. after hearing the rumors you cant cut them, i opted to never try them on anything. i have a friend that swears by them, but to be hionest he wouldnt know the difference if they worked or not.
 
Slot depth would have no real effect on "unequal" braking. If you cut them so deep the slots went away maybe, but again, its a temperature thing, not a change in braking force directly. Most of the rotors I have seen have a pretty deep chamfer on them, you'd have to cut them pretty deep to eliminate it completely, and then you could still re-chamfer them. But keep in mind even the stock rotors start out at 1", and can only be turned down to .940", which only works out to .030" cut on each side. That wouldn't get rid of the chamfer on my rotors.

I've never actually heard that the drilled/slotted rotors couldn't be cut, but then again, I haven't needed to have a set cut yet. I'm not surprised though, the problem with cutting them would come up with the cutting tool chattering in and out of the holes/slots, running the risk of breaking the tooling, which is likely why places don't want to cut them. Not that it can't be done, but its not a "set it and forget it" type operation anymore, you'd actually have to pay attention to what you were doing and know enough to check things out when you were done to make sure they were still chamfered etc. So if the big retail brake chains don't want to touch them I wouldn't be surprised.

On that note, on looking at my drilled and slotted rotors, I don't see a minimum thickness stamped on them, which may or may not mean anything. Most of the rotors I see these days do not have much distance between stock and minimum, after wear and tear maybe 1 good cut, they really aren't parts that you can use and re-use like you used to. As I mentioned, the stock rotors can only have a total of .060" cut off them. That isn't much, especially when you split it between 2 sides!

I run drilled and slotted 11.75" rotors on my Challenger, as you can see in the pics. They were $140 with shipping, making them cheaper than a lot of stock replacements. And given that I'd like my car to eventually see some road course time, I went with drilled and slotted. I'm not sure what these cars usually see in terms of mileage between brake pad changes, but I doubt its often enough to worry about the financial impact of having to replace the rotors with the pads. I drove the living piss out my '04 SRT4, and had over 40k miles on the front pads with room to spare when I sold it. The Challenger weighs an extra 600 lbs (srt4=2900 lbs), but my brakes are bigger too. :-D . And if you ever went "metal to metal" on your rotors, with only a .060" cut to start with you'd have to toss them anyway.

IMG_3766copy.jpg
 
There was a machine shop connected to a Napa store in my area, that had a tool grinder of sorts combined on their very large turning machine. That would be the ticket on S/D rotors8) Anyone seen these? They gave ya a beautiful job.
 
1968FormulaS340 said:
It really doesn't do anything for a street car.
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For that matter, even road race and oval track guys don't run drilled rotors that much anymore, and they often heat their brakes to a glowing red. About the only racing applications you see cross drilled rotors in these days are sport bikes (where it's purely a weight saving measure) and Porsches (which use teeny tiny, cast-in holes, and even then this may be cosmetic).
 
I autocrossed an Opel Manta years ago. Drilled the rotors in a nice geometric pattern. I noticed ZERO difference. Turned out to be a waste of time.
 
1968FormulaS340 said:
I may be wrong but I think the biggest thing is the risk of damage to the cutting equipment.

Better to tell one customer "NO" than to tell 10 customers "We can't" because our machine is down.
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yea my auto shop at school did a set for our teacher and it was a big headache having to slow cut them multiple times only taking like a thousandth or two at a time. for the time in labor that it would have cost to cut them with out breaking anything or ruining the rotor could have paid for two or three sets of normal rotors.
 
72bluNblu said:
Slot depth would have no real effect on "unequal" braking. If you cut them so deep the slots went away maybe, but again, its a temperature thing, not a change in braking force directly. Most of the rotors I have seen have a pretty deep chamfer on them, you'd have to cut them pretty deep to eliminate it completely, and then you could still re-chamfer them. But keep in mind even the stock rotors start out at 1", and can only be turned down to .940", which only works out to .030" cut on each side. That wouldn't get rid of the chamfer on my rotors.

I've never actually heard that the drilled/slotted rotors couldn't be cut, but then again, I haven't needed to have a set cut yet. I'm not surprised though, the problem with cutting them would come up with the cutting tool chattering in and out of the holes/slots, running the risk of breaking the tooling, which is likely why places don't want to cut them. Not that it can't be done, but its not a "set it and forget it" type operation anymore, you'd actually have to pay attention to what you were doing and know enough to check things out when you were done to make sure they were still chamfered etc. So if the big retail brake chains don't want to touch them I wouldn't be surprised.

On that note, on looking at my drilled and slotted rotors, I don't see a minimum thickness stamped on them, which may or may not mean anything. Most of the rotors I see these days do not have much distance between stock and minimum, after wear and tear maybe 1 good cut, they really aren't parts that you can use and re-use like you used to. As I mentioned, the stock rotors can only have a total of .060" cut off them. That isn't much, especially when you split it between 2 sides!

I run drilled and slotted 11.75" rotors on my Challenger, as you can see in the pics. They were $140 with shipping, making them cheaper than a lot of stock replacements. And given that I'd like my car to eventually see some road course time, I went with drilled and slotted. I'm not sure what these cars usually see in terms of mileage between brake pad changes, but I doubt its often enough to worry about the financial impact of having to replace the rotors with the pads. I drove the living piss out my '04 SRT4, and had over 40k miles on the front pads with room to spare when I sold it. The Challenger weighs an extra 600 lbs (srt4=2900 lbs), but my brakes are bigger too. :-D . And if you ever went "metal to metal" on your rotors, with only a .060" cut to start with you'd have to toss them anyway.

IMG_3766copy.jpg
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Out of curiousity, where did you buy your rotors from. I'm trying to find a set like yours that will work on a stock Dakota spindle. I'm converting to viper calipers and I want crossed drilled and slotted rotors as well. I'd love to find a set of 13" rotors but I can live with the 11.75 if they will work with my truck spindle. Shoot me a pm or something please.
 
Slotted are actually more effective, but the drilled rotors look nice. I have used Firm Feels pads with good results. However, stepping up to the 13" cobr stuff with Hydroboost is a whole different league. Who cuts rotors anymore? If they are warping, cutting off material isn't going to solve anything. The parts are so cheap its ridiculous to cut rotors anymore.
 
My understanding behind the idea of drilled and slotted rotors were to minimize the build-up of brake dust (which retains heat) and to provide more surface area for heat dissipation. Besides the risk of cracking the casting or damaging the rotor surface, removing metal is going to require either re-balancing the rotor or balancing the wheel/tire/brake rotor as a complete assembly. (i.e. spin balance on the car for those of you old enough to remember that stuff.)
 
If you do this on a cnc machine, the amount of material removed should not undo the balance of the rotor, provided that you did not remove any balance weights from the vented rotor and drilled thru the weights. When I did this to mine, we rechecked the balance and it was still spot on, but of course, there are those oddities that pop up sometime.
 
Do not drill rotors. you create sharp edges which WILL crack. buy pre drilled rotors from a reputable source as the like was said holes are already there and have been done properly to avoid cracking.
 
You MUST CHAMFER the holes, forgot to add that on my last post.
 
Spudmaster said:
I have been toying with the idea of drilling my 12 inch rotors to aid the stopping power of the system. Has anybody done this ?
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Drilled rotors have nothing to do with better braking or cooler brakes. They are drilled to lighten them. We run them on both our drag car and road race car. This info comes directly from Wilwood and Hawk.

Garland
 
Why did this thread come back.......


You will see NOTHING from slotted or drilled rotors on the street. NOTHING!

At the track you will see nothing unless you have a very serious track car that can make use of them.

Extra cost for looks only on a street car.
 
1968FormulaS340 said:
At the track you will see nothing unless you have a very serious track car that can make use of them.
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And sometimes then, the difference you see is a lot of cracking. As Xstream_1 noted, it's really just a weight saving measure, and not a good choice for a track car but can make sense for drag applications or motorcycles.
 
Can't argue with the " COOL " factor.
 
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