slotted rotors or drilled and slotted??
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Honda-Tech Member
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slotted rotors or drilled and slotted??
aye wats up so i was looking around for new rotors for my crx but i hearing to just get slotted rotors cuz as soon u drill holes in it u make it weaker?
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Joined: Jun 2004
Posts: 7,539
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From: Sherman Oaks, CA, United States
Re: slotted rotors or drilled and slotted??
Yes, drilling holes in a rotor is retarded.
Rotors that are meant to be "cross drilled", actually have the holes cast into them, they aren't drilled.
That said, anything other than normal blank rotors is a waste. If you're doing it for cosmetics, that's a personal choice, but don't think they offer any advantage, as they don't.
Rotors that are meant to be "cross drilled", actually have the holes cast into them, they aren't drilled.
That said, anything other than normal blank rotors is a waste. If you're doing it for cosmetics, that's a personal choice, but don't think they offer any advantage, as they don't.
Honda-Tech Member
Joined: Nov 2003
Posts: 201
Likes: 0
From: Oshawa, On, Canada
Re: slotted rotors or drilled and slotted??
Yes, drilling holes in a rotor is retarded.
Rotors that are meant to be "cross drilled", actually have the holes cast into them, they aren't drilled.
That said, anything other than normal blank rotors is a waste. If you're doing it for cosmetics, that's a personal choice, but don't think they offer any advantage, as they don't.
Rotors that are meant to be "cross drilled", actually have the holes cast into them, they aren't drilled.
That said, anything other than normal blank rotors is a waste. If you're doing it for cosmetics, that's a personal choice, but don't think they offer any advantage, as they don't.
These guys are all right. Slots and Drilled holes have their place, 99% if the time its not on Hondas. Only maybe when your car is a hardcore dedicated track car could they come into play. A blank rotor will most likely work best for your car.
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Joined: Mar 2008
Posts: 75
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From: Oklahoma City, OK, U.S.
Re: slotted rotors or drilled and slotted??
Quoted from 3geez...
What was wrong with the old ones? ...or did you just buy the new ones for the cool factor of the c/d look?
The reason I ask is because if the old rotors were good (ie. no pulsating pedal upon braking), then they are still true. You can just slap them back on, and with the new pads you'll be back in business and without the shake or any further expenses.
If the new rotors are warped already, there's a slight chance they were slightly off when you got them, in which case it might be worth the try to get them turned. The only thing you have to keep in mind is that every time you get a rotor turned, you're making the material thinner which means it will heat up faster and be more prone to warpage down the road.
As for the argument of cross drilled, slotted, both, or blanks, I've had lengthy conversations with Brembo, Baer, and some very willing and knowledgeable guys over at Willwood, and they were pretty much in complete agreement with these facts:
Cross drilled: This practice was used in racing applications to reduce weight of the rotating masses. It was also done promote better heat dissipation on the old steel rotors with the older (less high-tech) compounds that pads use to be made of. Finally, it was also believed to allow off-gassing of the pads to escape from the contact surface faster instead of acting as a lubrication between the rotor and pad surfaces which would make the braking less effective.
There are disadvantages to consider as well. Cross-drilled rotors are significantly weaker than a 'blank' or solid rotor of the identical material. This has proven itself time and again to cause a pre-mature cracking of the rotor which deems it useless.
Sounds like all positives with not too many negatives right? Well, yes, but things have come a long way since then.
Slotting: These slots cut into rotors will allow the off-gasses to escape, and the slotting can (somehow, but I don't completely understand it) pull the the pad back to the surface of the rotor and promote its 'bite' under heavy braking. Because the rotor surface is only gouged and not drilled through, they are structurally much stronger than the cross-drilled rotors. But because the surface is slightly compromised, they will cause the rotor to wear or warp faster, and because they're making your braking more effective, they will wear the pads a bit faster than a blank as well.
Dimpled: This gives the 'cool' look of cross-drilling without the negative side effects of cracking. However, the dimpling has proven not to do much of anything with regards to anything performance oriented. They just look pretty cool. But again, you're compromising the surface of the rotor, so it too will warp and/or wear faster than a blank.
Blank: While this is far more boring, and less aestetically pleasing than a cross-drilled, or slotted rotor, it does withstand more daily driving punishment than really any other rotor treatment. These will be the least likely to warp. While they will probably not dissipate off-gassing of rotor-to-pad quite as well as the slotted, they will do a damn good job of stopping you on command.
At this point, the materials used in rotor and pads are far superior to what they were when the cross-drilling was the thing to do. The newer rotors are stronger, lighter, and the pads are much less prone to heat exhaustion and can deliver great bite even under abuse. (Now that's providing you pay up for good pads as compared to the economy crap pads/rotors available for dirt cheap.) With nearly all cars (and certainly an even greater percentage of race-applications) the rotors are now 'vented' which means two rotor surfaces with a cavity (vents) between the two surfaces. This hugely helps with heat dissipation and cooling, and in turn greatly extends their life.
So at the end of the day, many cross-drilled rotors may look good, but it's really an older technology that doesn't really have a practical application in race purposes. The slotted would be the way I'd go if I'm racing the car, bearing in mind that my rotors/pads will not last as long, but might be a teensie-tiny bit more effective than blanks.
All that said, I currently have Brembo factory cross-drilled rotors both front and back, and Axxis Metal Master Ceramic pads front and back. I did drive it very hard when I was driving it regularly, and never cracked or warped a rotor. And as for the pads, I'm pretty much sold on using these for the foreseeable future. They actually bite more as they warm up. :dunno:
Anyway, sorry for the rambling, but hope it helps. If not, please disregard.
The reason I ask is because if the old rotors were good (ie. no pulsating pedal upon braking), then they are still true. You can just slap them back on, and with the new pads you'll be back in business and without the shake or any further expenses.
If the new rotors are warped already, there's a slight chance they were slightly off when you got them, in which case it might be worth the try to get them turned. The only thing you have to keep in mind is that every time you get a rotor turned, you're making the material thinner which means it will heat up faster and be more prone to warpage down the road.
As for the argument of cross drilled, slotted, both, or blanks, I've had lengthy conversations with Brembo, Baer, and some very willing and knowledgeable guys over at Willwood, and they were pretty much in complete agreement with these facts:
Cross drilled: This practice was used in racing applications to reduce weight of the rotating masses. It was also done promote better heat dissipation on the old steel rotors with the older (less high-tech) compounds that pads use to be made of. Finally, it was also believed to allow off-gassing of the pads to escape from the contact surface faster instead of acting as a lubrication between the rotor and pad surfaces which would make the braking less effective.
There are disadvantages to consider as well. Cross-drilled rotors are significantly weaker than a 'blank' or solid rotor of the identical material. This has proven itself time and again to cause a pre-mature cracking of the rotor which deems it useless.
Sounds like all positives with not too many negatives right? Well, yes, but things have come a long way since then.
Slotting: These slots cut into rotors will allow the off-gasses to escape, and the slotting can (somehow, but I don't completely understand it) pull the the pad back to the surface of the rotor and promote its 'bite' under heavy braking. Because the rotor surface is only gouged and not drilled through, they are structurally much stronger than the cross-drilled rotors. But because the surface is slightly compromised, they will cause the rotor to wear or warp faster, and because they're making your braking more effective, they will wear the pads a bit faster than a blank as well.
Dimpled: This gives the 'cool' look of cross-drilling without the negative side effects of cracking. However, the dimpling has proven not to do much of anything with regards to anything performance oriented. They just look pretty cool. But again, you're compromising the surface of the rotor, so it too will warp and/or wear faster than a blank.
Blank: While this is far more boring, and less aestetically pleasing than a cross-drilled, or slotted rotor, it does withstand more daily driving punishment than really any other rotor treatment. These will be the least likely to warp. While they will probably not dissipate off-gassing of rotor-to-pad quite as well as the slotted, they will do a damn good job of stopping you on command.
At this point, the materials used in rotor and pads are far superior to what they were when the cross-drilling was the thing to do. The newer rotors are stronger, lighter, and the pads are much less prone to heat exhaustion and can deliver great bite even under abuse. (Now that's providing you pay up for good pads as compared to the economy crap pads/rotors available for dirt cheap.) With nearly all cars (and certainly an even greater percentage of race-applications) the rotors are now 'vented' which means two rotor surfaces with a cavity (vents) between the two surfaces. This hugely helps with heat dissipation and cooling, and in turn greatly extends their life.
So at the end of the day, many cross-drilled rotors may look good, but it's really an older technology that doesn't really have a practical application in race purposes. The slotted would be the way I'd go if I'm racing the car, bearing in mind that my rotors/pads will not last as long, but might be a teensie-tiny bit more effective than blanks.
All that said, I currently have Brembo factory cross-drilled rotors both front and back, and Axxis Metal Master Ceramic pads front and back. I did drive it very hard when I was driving it regularly, and never cracked or warped a rotor. And as for the pads, I'm pretty much sold on using these for the foreseeable future. They actually bite more as they warm up. :dunno:
Anyway, sorry for the rambling, but hope it helps. If not, please disregard.
Honda-Tech Member
Joined: May 2007
Posts: 264
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From: Banbury, UK
Re: slotted rotors or drilled and slotted??
Quite a bit of miss information on the real technical side of things when it comes to disc finish.
Drilled discs were used in the old days when asbestos pads outgassed a lot, and it was simply to "evacuate" that small layer of gas to keep the pedal from feeling mushy.
These days its only used on some very light race cars, like D-sports and light open wheels, or motorcycles in order to reduce moment of inertia and unsprung weight.
It was never meant for cooling, as the holes decrease the overall mass of the disc therefore the thermal capacity and the holes cast or drilled will always be a stress point and develop cracks. End of story.
Slotted discs are used today in racing for a few reasons. If the slot design is good and was actually studied by competent engineers vs just something thrown on the face of the disc in any direction, leght, depth, etc... it will indeed increase initial bite, and overall brake torque, due to more leading edges "biting" on the pad. While at the same time, allowing the almost none (these days) gas layer to escape and clean the pad face of debris, etc.
If the slots are not of good design, it will work against the principle and wont do much but the "cons" of the slotted disc - increase pad wear and make noise.
Dimpled discs dimpled discs are used by some companies as a street/aftermarket option, again if well placed on the face of the disc, it will allow for some pad outgassing and cleaning. The pro's are less noise and wear than a slotted design.
Smooth discs best for street, most pad and disc life, with only slightly less braking torque than a good slotted disc.
As for disc warping, it has nothing to do with the face of the disc and more with the disc is attachment. Good full floating discs(AP's, PFC's, Race Brembo's and Alcons) are almost impossible to warp. If they're rigidly mounted or 1 piece it will have more tendencies to warp due to the different expanssion rates across the whole disc.
Hope this helps.
Drilled discs were used in the old days when asbestos pads outgassed a lot, and it was simply to "evacuate" that small layer of gas to keep the pedal from feeling mushy.
These days its only used on some very light race cars, like D-sports and light open wheels, or motorcycles in order to reduce moment of inertia and unsprung weight.
It was never meant for cooling, as the holes decrease the overall mass of the disc therefore the thermal capacity and the holes cast or drilled will always be a stress point and develop cracks. End of story.
Slotted discs are used today in racing for a few reasons. If the slot design is good and was actually studied by competent engineers vs just something thrown on the face of the disc in any direction, leght, depth, etc... it will indeed increase initial bite, and overall brake torque, due to more leading edges "biting" on the pad. While at the same time, allowing the almost none (these days) gas layer to escape and clean the pad face of debris, etc.
If the slots are not of good design, it will work against the principle and wont do much but the "cons" of the slotted disc - increase pad wear and make noise.
Dimpled discs dimpled discs are used by some companies as a street/aftermarket option, again if well placed on the face of the disc, it will allow for some pad outgassing and cleaning. The pro's are less noise and wear than a slotted design.
Smooth discs best for street, most pad and disc life, with only slightly less braking torque than a good slotted disc.
As for disc warping, it has nothing to do with the face of the disc and more with the disc is attachment. Good full floating discs(AP's, PFC's, Race Brembo's and Alcons) are almost impossible to warp. If they're rigidly mounted or 1 piece it will have more tendencies to warp due to the different expanssion rates across the whole disc.
Hope this helps.
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