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Not sure if this is where he was going with it or not but, from a machining standpoint, the reason not having the back chamfered/countersunk is that any and all sharp corners on anything you machine are susceptible to cracking, especially with the heat cycles seen on brake rotors. There are ways to add back chamfers but that adds a lot of time to the machining process, and in turn the cost.
 

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I'd say yes slotted but be careful with drilled....they will crack by the drilled spots, more so with a heavy truck pulling as it makes heat, couple that with possible water and they crack, I've had drilled crack and never had trouble after switching to just slotted...JMHO
 

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for those for cross drilled and slotted rotors here ya go. I know this is about race cars but with the heat our brakes see from heavy loads i would say this does have some say so about our brakes

AP Racing:
"Grooves improve 'cleaning' of the pad surfaces and result in a more consistent brake performance. Grooved discs have a longer life than cross-drilled discs."

Baer:
"What are the benefits to Crossdrilling, Slotting, and Zinc-Washing my rotors? In years past, crossdrilling and/or Slotting the rotor for racing purposes was beneficial by providing a way to expel the gasses created when the bonding agents employed to manufacture the pads...However, with today's race pad technology, 'outgassing' is no longer much of a concern...Slotted surfaces are what Baer recommends for track only use. Slotted only rotors are offered as an option for any of Baer's offerings."

Darrick Dong; Director of Motorsports at Performance Friction: "Anyone that tells you that drilling makes the disc run cooler is smoking crack."

Waren Gilliand:
(Warren Gilliland is a well-known brake engineer in the racing industry and has more than 32 years experience in custom designing brake systems ...he became the main source for improving the brake systems on a variety of different race vehicles from midgets to NASCAR Winston Cup cars.) "If you cross drill one of these vented rotors, you are creating a stress riser that will encourage the rotor to crack right through the hole. Many of the rotors available in the aftermarket are nothing more than inexpensive offshore manufactured stock replacement rotors, cross drilled to appeal to the performance market. They are not performance rotors and will have a corresponding high failure rate"

Grassroots Motorsports:
"Crossdrilling your rotors might look neat, but what is it really doing for you? Well, unless your car is using brake pads from the '40s and 50s, not a whole lot. Rotors were first drilled because early brake pad materials gave off gasses when heated to racing temperatures, a process known as "gassing out." ...It was an effective solution, but today's friction materials do not exhibit the some gassing out phenomenon as the early pads. Contrary to popular belief, they don't lower temperatures. (In fact, by removing weight from the rotor, they can actually cause temperatures to increase a little.) These holes create stress risers that allow the rotor to crack sooner, and make a mess of brake pads--sort of like a cheese grater rubbing against them at every stop. Want more evidence? Look at NASCAR or F1. You would think that if drilling holes in the rotor was the hot ticket, these teams would be doing it...Slotting rotors, on the other hand, might be a consideration if your sanctioning body allows for it. Cutting thin slots across the face of the rotor can actually help to clean the face of the brake pads over time, helping to reduce the glazing often found during high-speed use which can lower the coefficient of friction. While there may still be a small concern over creating stress risers in the face of the rotor, if the slots are shallow and cut properly, the trade-off appears to be worth the risk. (Have you looked at a NASCAR rotor lately?)

Power Slot:
"At one time the conventional wisdom in racing circles was to cross-drill brake rotors to aid cooling and eliminate the gas emitted by brake pads. However, today's elite teams in open wheel, Indy and Trans Am racing are moving away from crack prone, cross-drilled brake rotors in favor of rotors modified with a fatigue resistant slotting process."

Stop Tech:
"StopTech provides rotors slotted, drilled or plain. For most performance applications slotted is the preferred choice. Slotting helps wipe away debris from between the pad and rotor as well as increasing the "bite" characteristics of the pad. A drilled rotor provides the same type of benefit, but is more susceptible to cracking under severe usage. Many customers prefer the look of a drilled rotor and for street and occasional light duty track use they will work fine. For more severe applications, we recommend slotted rotors." (Note that even though Stop Tech sells both drilled and slotted rotors they do not recommend drilled rotors for severe applications.)

Wilwood:
Q: Why are some rotors drilled or slotted?
A: Rotors are drilled to reduce rotating weight, an issue near and dear to racers searching for ways to minimize unsprung weight. Drilling diminishes a rotor's durability and cooling capacity."
 

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Ok, I think I can help a little here considering how many rotors and pads I've had to swap out in my short life. If your looking to get some brake rotors for your hauling rig ANYTHING made by EBC STOP TECH or POWER SLOT, will reduce your unladen panic stops about 10% (Bedding pads and rotors is paramount) when paired with proper pads. And I'm sure their resistance to fade will only multiply the effectiveness when your hauling down your rig with whatever your pulling.

However, these rotors can and do chew less aggressive "factory" pads up from what I've seen due to them being made with more wear resistant material. Pair them with something that's more aggressive than stock. My personal faves for DD Rigs that don't do (much, like my S-10, which has hauled many a Liquid Anhydrous trailer) hauling are EBC "greenstuffs". If your going to tow often "Redstuffs" are good aggressive pads, but they are hard to ease into because of their initial bite, but they do wear down faster. However, yellowstuffs are even better for trucks, but, they do dust pretty heavily compaired to greens and reds. I haven't tried the Orangestuffs, but they seem to be a good pad.

The only ones I will say STAY AWAY FROM, are bluestuffs. But I don't know of any application for them on a truck... they are Smi race pads, you actually have to heat them up.

Now if you can't get ahold of EBCs anything made by HAWK is a good compromise. They do wear down a bit quicker, but they are quiet.

As for rotors Slotted are nice, but solids are almost as good, ALMOST.

Another upgrade to consider is SS brake lines, but that's a personal preference thing. It helps with feel more than shorter stopping distances.
 

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Not sure if this is where he was going with it or not but, from a machining standpoint, the reason not having the back chamfered/countersunk is that any and all sharp corners on anything you machine are susceptible to cracking, especially with the heat cycles seen on brake rotors. There are ways to add back chamfers but that adds a lot of time to the machining process, and in turn the cost.
i dont know where he was going with it, there is no way in hell that the brake rotor manufacturer is going to take the time to even attempt to break those inside edges from the top side. and by the millions that have been sold and probably abused, the current technology evidently works lol.

im actually thinking about getting some stock disc's and drilling them myself, should be pretty easy actually.
 

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I have R1 concepts drilled & slotted rotors and I love them. Only had them on for a couple thousand miles but so far no complaints.
 

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i dont know where he was going with it, there is no way in hell that the brake rotor manufacturer is going to take the time to even attempt to break those inside edges from the top side. and by the millions that have been sold and probably abused, the current technology evidently works lol.

im actually thinking about getting some stock disc's and drilling them myself, should be pretty easy actually.
:rof That's a good one!
 

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i dont know where he was going with it, there is no way in hell that the brake rotor manufacturer is going to take the time to even attempt to break those inside edges from the top side. and by the millions that have been sold and probably abused, the current technology evidently works lol.

im actually thinking about getting some stock disc's and drilling them myself, should be pretty easy actually.
I agree. Other than the ones manufactured for pure racing applications, there would be no reason. I was just saying from a technical standpoint that COULD be an issue. One thing you can do is look for something called a cogsdill, which is a very simple way to at least deburr and break the edge of the hole.
 

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I agree. Other than the ones manufactured for pure racing applications, there would be no reason. I was just saying from a technical standpoint that COULD be an issue. One thing you can do is look for something called a cogsdill, which is a very simple way to at least deburr and break the edge of the hole.
interesting, never seen a cogsdill before, thanks!...id probably just modify a boring bar, never programmed for it before personally but i have had it explained how to do it.
 

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I'm not saying it's impossible, in fact, it is a relatively simple operation, but why would you? If you are going to go through the work to properly locate all the holes and chamfer them, might as well slot them instead.
 

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I agree and personally think that there no reason to worry about the back of the rotors, if you are that worried about them, use these rotors, they are "dimpled" so you don't have to worry about the interior sides. Or as many have said, just go with the slotted versions. It's all personal choice and I bet that you will find people that have cracked rotors with light driving, and people who have never cracked them with heavy driving?????
 

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Reign in Blood
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I'm not saying it's impossible, in fact, it is a relatively simple operation, but why would you? If you are going to go through the work to properly locate all the holes and chamfer them, might as well slot them instead.
yeah slotting would be hand over fist easier...1/4 ball...done lol
 

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Late to the party here, found the link in the latest newsletter. I am glad to see everyone providing great information about the drilled vs slotted rotor debate! We always recommend a blank or slotted rotor to our heavy duty truck customers. Good information in this thread! :thumb
 

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Bought R1 concepts from Willie Manners on here and and added the ss brake lines also well worth the money in my opinion bought them for my step dads truck also and he raves about them.
 

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I'm not saying it's impossible, in fact, it is a relatively simple operation, but why would you? If you are going to go through the work to properly locate all the holes and chamfer them, might as well slot them instead.
masterCAM says 4 minutes per side so figure more like 6-8...not too bad, granted thats not properly dimensioned just a test program. figure 30 minutes or so to make a quick fixture to bolt the rotors to. the way i would do it is all 4 one side, then flip reset the 2 tools and do the opposite side.

you didnt think i was going to entertain doing this on a drill press now did you :neener

2 tools, 1/2 center drill, 1/4 drill...use the center drill to spot the hole and also create the chamfer, then drill
rotortest.jpg
 

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