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replacement rotor question
Hey all,
I suspect that my rotors may be in need of replacement soon. Or I will just have them turned, but I still want to ask the question. I don't want to get a big brake kit right now cause of the cost. A friend of mine gets really large discounts at an auto parts store, and can get me powerslot rotors for cheap. I'm using the axxis deluxe plus pads right now, and will most likely continue to use them because of the minimal brake dust.
Should I stick with OEM replacements or get the powerslot rotors?
Any other suggestions for OEM size replacement rotors?
TIA
Simpson
| | Reply » replacement rotor question |
From what I have gathered, I would stick with OEM. Dave Z. once suggested that the sloted or drilled rotors could have a "cheese grater" effect on the brake pads and therefore they wouldn't last as long as with normal, OEM rotors.
| | Reply » replacement rotor question |
Quote: | From what I have gathered, I would stick with OEM. Dave Z. once suggested that the sloted or drilled rotors could have a "cheese grater" effect on the brake pads and therefore they wouldn't last as long as with normal, OEM rotors. |
I actually purchased some drilled and slotted Brembo rotors for a Honda Accord (crazy, I know), but the pads lasted for 70k miles...so I would say that there appeared to be no undue wear. But really, the stock rotors are fine...I wouldn't bother with the slots or holes. They do look cool though! 
| | Reply » replacement rotor question |
Quote: | I actually purchased some drilled and slotted Brembo rotors for a Honda Accord (crazy, I know), but the pads lasted for 70k miles...so I would say that there appeared to be no undue wear. But really, the stock rotors are fine...I wouldn't bother with the slots or holes. They do look cool though! | Drilled or slotted rotors give you slightly improved bite in exchange for a small increase in pad wear. In addition, drilled rotors have the advantage of saving you 1/4 to 1/3 pound of weight per rotor. On the other hand, under race conditions (or track events & high speed driving schools) drilled rotors tend to crack sooner than plain or slotted rotors. This is not an issue for a strictly street driven car.
Brembo does not make drilled AND slotted rotors. So the rotors you purchased for your Honda either started life as Brembo plain rotors and were machined by a 3rd party or they were counterfeit rotors produced in Asia, typically sold on eBay. Drilling and slotting weakens the rotors and nobody who knows what they are doing will manufacture them. When you see drilled AND slotted Brembo rotors, run away!
PowerSlot rotors are decent quality. I would have no hesitation using them. In fact, they can help offset the low cold bite of the Axxis Deluxe Plus pads. I think it's a fine combination.
| | Reply » replacement rotor question |
Yes, my Brembos were drilled and slotted by an outside source, who then retailed them....They appeared to have been carefully done, with all holes chamfered and radiused, but like I said, I am certain, that plain axially vented Brembos would have been fine. Dave, you are much more the expert than me, but my good friend has a PHD in material science (MIT) and scoffed at my purchase, saying that while I might save weight, the metal is there to act as a heat sink too....less metal, less capacity. He also reminded me that those holes were not improving cooling without ducting....anyway, live and learn. I agree with what you are saying about them perhaps helping in preventing "glazing" of the pad and improved "bite".
| | Reply » replacement rotor question |
Quote: | Yes, my Brembos were drilled and slotted by an outside source, who then retailed them....They appeared to have been carefully done, with all holes chamfered and radiused, but like I said, I am certain, that plain axially vented Brembos would have been fine. Dave, you are much more the expert than me, but my good friend has a PHD in material science (MIT) and scoffed at my purchase, saying that while I might save weight, the metal is there to act as a heat sink too....less metal, less capacity. He also reminded me that those holes were not improving cooling without ducting....anyway, live and learn. I agree with what you are saying about them perhaps helping in preventing "glazing" of the pad and improved "bite". | Your friend is right. There is no advantage in cooling capacity of a drilled rotor over a plain rotor. In fact, if you take away 1/4 pound of weight, you've reduced the thermal mass and, all else being equal, that rotor will get slightly hotter during a given stop. This should be consistant with what your friend learned in his thermodynamics classes. However, there is some local thermal advantage at the pad/rotor interface where hot gasses can be vented away from the pad. So the pad does run slightly cooler on a drilled (or slotted) rotor.
The rotor does two jobs. It converts kinetic energy to heat and acts as a thermal capacitor (as your friend pointed out). Or, for the non-engineers out there, it's like using a bigger coffee mug to hold the same amount of hot coffee. The bigger mug is cooler in your hands because the heat from the coffee is distributed throughout more mass.
But that's only half the story. The rotor also sheds heat via several mechanisms: radiation, convection, and conduction. Radiation dominates, at about 50% of the total. Radiation is a function of the rotor surface area. If you do the math, drilling a rotor does not materially affect the radiation cooling. Convective cooling is a function of airflow over and through the rotor. Here's where many vendors make incorrect claims about the "cooling advantage" of drilled rotors. But it doesn't fly. Air is pumped through the rotor by the internal vanes. Air does not suddenly stop and take a 90 degree detour to go out one of the drilled holes. And finally, there's conduction. This is the "bad" cooling that takes place at the expense of your wheel bearings and your brake fluid. Convective and conductive cooling are each about 25% of the total. (Those percentages change if you have a bumper mounted air intake feeding a flexible tube that forces air through the center of the rotor.)
Bottom line, the improved bite and the slight weight savings are the benefits to drilled rotors, with some reduction in pad temperature. And 1/3 pound of rotating mass is not something to scoff at. In fact, Bill Auberlin will occasionally run drilled rotors on his BMW in the SPEED World Challenge qualifying sessions, only to replace them with slotted rotors for the actual races. He wants every bit of weight savings during qualifying to compensate for the "reward weight" they've piled on his car. But he doesn't trust drilled rotors to last through an entire race.
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replacement rotor question