Cross Drilled Rotors for IS
04-27-07, 12:13 AM
#31
Lexus Test Driver
04-27-07, 10:31 AM
#32
Lexus Champion
Anyone who says rotors with slots or c/d holes make no performance difference has never out driven their brakes. I warped the stock rotors on my IS350 the first time I really had a chance to drive the car to it's potential {and beyond}. If you never brake from 120+ hard, repeatedly then stay stock. If you are road or track racing and actually pushing hard you'll see, your stock rotors warp and your brakes will fade. Every race car in the world has large diameter cross drilled/slotted or both, rotors for a reason. If they made a ceramic disk for the car then you would'nt hav to go cd/s/v but since they don't........ I have yet to warp the new brakes and i've flogged the &#@$ out of them.
When you cross drill the rotors (like most aftermarket manufacturers do with an emphasis on looks/bling) you are:
1. reducing rotor mass that reduces heat capacity. If you look at my previous post on this, take 2 identical rotors and cross drill one of them. Put them on identical cars and perform the same stops. The cross drilled rotor will always be hotter after the stops regardless of the number of stops. You can't argue against physics here.
2. reducing rotor mass and surface area that will effectively reduce the rotors ability radiate the heat that is built up. You need surface area to dissipate heat. The little holes will actually decrease the effective surface material that will help dissipate the heat.
What are these race cars you mention that all have cross drilled/slotted rotors? Any F1, Indy, Nascar teams using cross drilled/slotted rotors?
There are some sports cars that use drilled rotors. The biggest distinction here is the size and number of holes they use. If you look at the rotors of a Ferrari, the total number/size of the holes probably amounts to about an 1/8 of the same on aftermarket rotors.
Here are a few excerpts from the manufacturers themselves:
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."
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."
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."
From 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."
tells you that drilling makes the disc run cooler is smoking crack."
04-27-07, 10:58 AM
#33
Tech Info Resource
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Anyone who says rotors with slots or c/d holes make no performance difference has never out driven their brakes. I warped the stock rotors on my IS350 the first time I really had a chance to drive the car to it's potential {and beyond}. If you never brake from 120+ hard, repeatedly then stay stock. If you are road or track racing and actually pushing hard you'll see, your stock rotors warp and your brakes will fade. Every race car in the world has large diameter cross drilled/slotted or both, rotors for a reason. If they made a ceramic disk for the car then you would'nt hav to go cd/s/v but since they don't........ I have yet to warp the new brakes and i've flogged the &#@$ out of them.
Originally Posted by http://www.onelapsupra.com/OneLap2002/OneLapSupra.htm
The only minor issue we’re having is that my cross-drilled front rotors are FUBARed. They are horridly warped now and have begun to develop hairline cracks at the vent holes. As soon as I get back home (or maybe sooner) I’m going to call and order the solid version replacements, no slotting or drilling for me. That stuff may look nice but it sucks for racing. I just hope these rotors last the rest of the event (I think they will).
04-27-07, 11:21 AM
#34
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04-27-07, 03:32 PM
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Ask Andi Baritchi (4th 2002 One Lap, 6th 2003 One Lap in his Supra) what he thinks about cross drilled rotors.
Obviously your experience tells you something different, but I'd suspect you had OEM pads in your IS350, and that's what caused your problem. In fact, I'd wager quite a bit of money that your rotors were not warped, but just had uneven deposits from the pads on them.
Obviously your experience tells you something different, but I'd suspect you had OEM pads in your IS350, and that's what caused your problem. In fact, I'd wager quite a bit of money that your rotors were not warped, but just had uneven deposits from the pads on them.
You are right, I was running a full OEM set up including pads, but i'm sure the rotors were out and not just accumulating deposits. I'm happpy with my BBK and have had no problems with warping, cracking ect. I'm sure the larger diameter disks compensate for the heat dissapating suface area potentially lost by the drill holes. If i ever encounter problems I'll post them for all to see.
04-27-07, 06:15 PM
#37
I am not defending slottend / drilled rotors at all (see above), but this statement isn't always true. Cooling requires surface area to the air, not the pad. Hence, slotted rotors will always increase surface area (with the air), and drilled rotors will sometimes increase surface area.
04-27-07, 06:49 PM
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So if cross drilled rotors are worse than standard rotors why do companies like Porsche, Ferrari, and Lamborghini still use them on their high performance sports cars?
04-27-07, 07:00 PM
#39
Tech Info Resource
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Look at the IS-F. It looks like it's been lowered at the factory. It has 19" wheels. It has 14.2" rotors. It's what's in style. The only good thing about this is the factory won't sacrifice proper handling for lowering where the aftermarket must do this because the aftermarket can't change the suspension pickup points. The factory can, and I'm sure they did to be certain the car's roll centers, roll couples, and roll axis are correctly located. That never happens with aftermarket.
Don't get me wrong, drilled rotors have their place. They are common in ALMS because they want to drop as much unsprung weight as possible and they don't care if they replace the rotors every race weekend. They are not practical if you are on a budget that doesn't support frequent replacement, and they are not necessary in any but the most competitive series where they are restricted by the rules regarding what brake setups they can run (i.e. no carbon/carbon brakes on production based cars.)
04-27-07, 09:18 PM
#41
Lexus Champion
I am not defending slottend / drilled rotors at all (see above), but this statement isn't always true. Cooling requires surface area to the air, not the pad. Hence, slotted rotors will always increase surface area (with the air), and drilled rotors will sometimes increase surface area.
04-27-07, 09:24 PM
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Because people expect this. It's no different for why they put massive heavy wheels on the cars. People expect it. It's fashionable. Bigger diameter wheels != better performance, it often makes real, measurable performance worse, but it's fashionable. Lexus wouldn't have 10% of the noise issues with the ISx50 if they had 16" or 17" wheels and tires with more sidewall to absorb road noise. But the market fashion police dictate 18" or larger wheels as what "everyone" wants. So we get 18" wheels. And drilled rotors.
Look at the IS-F. It looks like it's been lowered at the factory. It has 19" wheels. It has 14.2" rotors. It's what's in style. The only good thing about this is the factory won't sacrifice proper handling for lowering where the aftermarket must do this because the aftermarket can't change the suspension pickup points. The factory can, and I'm sure they did to be certain the car's roll centers, roll couples, and roll axis are correctly located. That never happens with aftermarket.
Don't get me wrong, drilled rotors have their place. They are common in ALMS because they want to drop as much unsprung weight as possible and they don't care if they replace the rotors every race weekend. They are not practical if you are on a budget that doesn't support frequent replacement, and they are not necessary in any but the most competitive series where they are restricted by the rules regarding what brake setups they can run (i.e. no carbon/carbon brakes on production based cars.)
Look at the IS-F. It looks like it's been lowered at the factory. It has 19" wheels. It has 14.2" rotors. It's what's in style. The only good thing about this is the factory won't sacrifice proper handling for lowering where the aftermarket must do this because the aftermarket can't change the suspension pickup points. The factory can, and I'm sure they did to be certain the car's roll centers, roll couples, and roll axis are correctly located. That never happens with aftermarket.
Don't get me wrong, drilled rotors have their place. They are common in ALMS because they want to drop as much unsprung weight as possible and they don't care if they replace the rotors every race weekend. They are not practical if you are on a budget that doesn't support frequent replacement, and they are not necessary in any but the most competitive series where they are restricted by the rules regarding what brake setups they can run (i.e. no carbon/carbon brakes on production based cars.)
Last edited by IS350PRO; 04-27-07 at 09:28 PM.
04-27-07, 09:38 PM
#44
Lexus Champion
16 or 17 inch wheels with more sidewall would compromise performance. I agree that 18 inch wheels are fashionable but if you wanted performance {less side wall flex} from smaller wheels you would have to go lower profile and you'd still get the road noise. Plus 16's would look retarded.
Most (if not all) of the R compound racing tires come in aspect ratios as tall as 50-55%
Given the choice of 40's series tires on the 18"s or 50 and 45 series tires on 16" and 17" wheels respectively, I'd definitely choose the 16" or 17"s and save the unsprung weight.
