WHY Blank rotors are better than cross drilled
02-11-2010, 04:59 PM
#11
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MANY OEMS and most sports car racing teams use slotted rotors. The Prosche Panamera comes with slotted rotors. Many OEMs use drilled rotors. These rotors are DESIGNED TO BE DRILLED and don’t crack.
02-11-2010, 06:24 PM
#12
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brake systems are designed to handle a specific amount of thermal stress, and most of this is managed by utilizing the rotor as a heat sink.
if a car is meant to have a 12 inch rotor with a mass of X and you put on a 12 in rotor with drilled holes (which certainly are stress risers and will cause cracks) you now have a mass of X-weight removed by drilling, and the systems is capable of handling less thermal stress on two fronts.
if the system was designed from the outset to use vented rotors, and they are cast not drilled. fine.
http://www.stoptech.com/tech_info/The%20Ph...g%20Systems.pdf
great read!
note the equations for stopping power that utilize swept area (which drilling decreases) and thermal absorption relative to mass (which drilling removes)
if a car is meant to have a 12 inch rotor with a mass of X and you put on a 12 in rotor with drilled holes (which certainly are stress risers and will cause cracks) you now have a mass of X-weight removed by drilling, and the systems is capable of handling less thermal stress on two fronts.
if the system was designed from the outset to use vented rotors, and they are cast not drilled. fine.
http://www.stoptech.com/tech_info/The%20Ph...g%20Systems.pdf
great read!
note the equations for stopping power that utilize swept area (which drilling decreases) and thermal absorption relative to mass (which drilling removes)
02-11-2010, 08:40 PM
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Originally Posted by Zoomie,Feb 11 2010, 07:24 PM
02-11-2010, 08:52 PM
#14
Originally Posted by BrakeExpert,Feb 11 2010, 04:05 PM
Sorry if I sound cocky or like a know it all, I don't mean to.
02-11-2010, 09:00 PM
#15
Originally Posted by BrakeExpert,Feb 11 2010, 05:04 PM
The part of the rotor exposed to the air cools at a different rate than the part coverd by the pad. This part can be thicker ever so slightly that when you take off and hit the brakes very soon after, this part is raised and the pad still wears it. This can create warped rotors. If you draw rings on the rotor where the holes are, you can see on some cars with cross drilled rotors that run really hot, that these rings are actaully noticable, and these holes can cause the rotor's thickness to vary more.
Maybe I'm not clarifying properly, but cross drilled discs can increase warpage.
Maybe I'm not clarifying properly, but cross drilled discs can increase warpage.
http://www.stoptech.com/tech_info/wp...rakedisk.shtml
02-11-2010, 09:29 PM
#16
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That was a screenname on other forums, people know me cause I do hybrid Honda brake upgrade for people cause I modify parts. I didn't know this forum was gonna bite my head off so much.
02-11-2010, 09:37 PM
#17
Originally Posted by Zoomie,Feb 11 2010, 10:24 PM
brake systems are designed to handle a specific amount of thermal stress, and most of this is managed by utilizing the rotor as a heat sink.
if a car is meant to have a 12 inch rotor with a mass of X and you put on a 12 in rotor with drilled holes (which certainly are stress risers and will cause cracks) you now have a mass of X-weight removed by drilling, and the systems is capable of handling less thermal stress on two fronts.
if the system was designed from the outset to use vented rotors, and they are cast not drilled. fine.
http://www.stoptech.com/tech_info/The%20Ph...g%20Systems.pdf
great read!
note the equations for stopping power that utilize swept area (which drilling decreases) and thermal absorption relative to mass (which drilling removes)
if a car is meant to have a 12 inch rotor with a mass of X and you put on a 12 in rotor with drilled holes (which certainly are stress risers and will cause cracks) you now have a mass of X-weight removed by drilling, and the systems is capable of handling less thermal stress on two fronts.
if the system was designed from the outset to use vented rotors, and they are cast not drilled. fine.
http://www.stoptech.com/tech_info/The%20Ph...g%20Systems.pdf
great read!
note the equations for stopping power that utilize swept area (which drilling decreases) and thermal absorption relative to mass (which drilling removes)
Heatsinks (which is what the rotors function as) dissipate heat through surface area - i.e. more surface area = more heat dissipation.
If it was all about mass, we wouldn't see vented rotors - just really thick, massive solid rotors.
But, it's not. The rotor has to be able to absorb heat from the friction, but it must also dissipate that heat. So while a cross-drilled rotor might not be able to absorb and hold as much heat, provided the size of the hole is appropriately sized the rotor will have more surface area to dissipate the heat instead of that heat building up in the rotor.
As for swept area - as Dan has rightly pointed out, the CoF (which is what counts when it comes to braking force) is not affected by surface area.
Big brake kits do two things - increase the torque (wider rotor = longer arm), increase surface area, improve brake modulation (fixed vs sliding caliper), and weigh less than stock (monoblock aluminum vs cast).
02-11-2010, 11:15 PM
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Originally Posted by BrakeExpert,Feb 11 2010, 10:29 PM
That was a screenname on other forums, people know me cause I do hybrid Honda brake upgrade for people cause I modify parts. I didn't know this forum was gonna bite my head off so much.
02-12-2010, 06:19 AM
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Originally Posted by Neutered Sputniks,Feb 11 2010, 10:37 PM
It's not as simple as you're making it out to be.
Heatsinks (which is what the rotors function as) dissipate heat through surface area - i.e. more surface area = more heat dissipation.
If it was all about mass, we wouldn't see vented rotors - just really thick, massive solid rotors.
But, it's not. The rotor has to be able to absorb heat from the friction, but it must also dissipate that heat. So while a cross-drilled rotor might not be able to absorb and hold as much heat, provided the size of the hole is appropriately sized the rotor will have more surface area to dissipate the heat instead of that heat building up in the rotor.
As for swept area - as Dan has rightly pointed out, the CoF (which is what counts when it comes to braking force) is not affected by surface area.
Big brake kits do two things - increase the torque (wider rotor = longer arm), increase surface area, improve brake modulation (fixed vs sliding caliper), and weigh less than stock (monoblock aluminum vs cast).
Heatsinks (which is what the rotors function as) dissipate heat through surface area - i.e. more surface area = more heat dissipation.
If it was all about mass, we wouldn't see vented rotors - just really thick, massive solid rotors.
But, it's not. The rotor has to be able to absorb heat from the friction, but it must also dissipate that heat. So while a cross-drilled rotor might not be able to absorb and hold as much heat, provided the size of the hole is appropriately sized the rotor will have more surface area to dissipate the heat instead of that heat building up in the rotor.
As for swept area - as Dan has rightly pointed out, the CoF (which is what counts when it comes to braking force) is not affected by surface area.
Big brake kits do two things - increase the torque (wider rotor = longer arm), increase surface area, improve brake modulation (fixed vs sliding caliper), and weigh less than stock (monoblock aluminum vs cast).
Coefficent of friction is not affected by area, by the definition of coefficent, but overall braking force IS.
Thermal capacity is dictated by mass, cooling is dictated by surface area. The balance of the two is where brakes need to be designed.
02-12-2010, 06:31 AM
#20
Originally Posted by Zoomie,Feb 12 2010, 07:19 AM
Coefficent of friction is not affected by area, by the definition of coefficent, but overall braking force IS.