Hi, many of the suppliers of advanced brake systems, like Tarox, offer grooved brake discs, sometimes even cross-drilled and grooved, whilst supercar makers like Ferrari and Lamborghini seem to stick with cross-drilled brake-discs. I mean if cross-drilled are good enough for Ferrari it should be good enough for me doing four or five trackdays a year... I have heard of people complaining about warped discs after trackdays and even cracked cross-drilled discs. Is this an issue if you stick to original items or just OEM discs? Just curious since my discs will have to be replaced pretty soon. What do you think? // Peter
Slotted only is less resistant to cracking I've been told. For the street either should be ok, and everyone thinks the drilled looks better.
The best brakes for high performance driving are plain faced rotors. Sloted and cross drilled rotors are for show. Cross drilled rotors crack and the loss in mass of the drilled and relieved area results in the rotor overheating more easily than without the cross drilling. Even the expensive Porsche rotors with cast in holes will crack. This is easy to understand if you know anything about stress in materials as they heat and cool differentially. Slotted rotors don't have the cracking problems that cross drilled have, but unless you are racing in the wet, they don't have any advantages* either. Pad wear is slightly accelerated. *With modern pad materials, the amount of outgassing is minimal (unlike the pads of the 1980s.)
Peter, interesting point about Ferrari and Lambo continuing to drill their rotors. I recently did a lot of research about these issues for a brake upgrade on my Viper. All the tuners and racing brake manufacturers that I spoke with said the same thing. With the advent of improved brake pad materials, the characteristics concerning heat build up and the need to remove the gasses created have been reduced to the point that drilling is no longer necessary or practiced for racing applications. I did notice yesterday, while examining about 6 550's and 575's, that the pattern and frequency of the holes varied from car to car and model to model. Maybe the Fiorano package has a different drill pattern? I suspect with just 4 or 5 track days it won't be an issue, but that is the current info from the experts I talked with. Hope that helps, John
Mitch, slotting is much more for cleaning friction material off the surface, otherwise, most pad's material will build up and tend to gouge the rotor's surface, especially toward the inner diameter of the friction surface. Simplistically, slots are used for scraping the abrasive dust from the pad/rotor interface. Yes, outgassing is not the issue. That's, as you know, handled during bedding of the pads. Millemiglia, et. al., drilling brake rotors is a Marketing (bling-bling) decision, that the engineers have determined will not hurt anything on a street driven vehicle. Best regards, Rob Schermerhorn
The purpose of cross-drilling and slotting is to help the friction pads to "off-gas," thus minimizing glazing of the pads. New friction materials do not off gas as much as older materials but there is still some advantage. There is no preference between drilling and slotting. Slotting was developed in order to minimize cracking due to stress risers caused by incorrect drilling practices used by some manufacturers. Quality manufactured rotors such as Brembo rotors are properly drilled and chamfered so this is not a problem. Drilled rotors however have a racier look and have retained their popularity
Cracks are a normal part of drilled discs. Cracks are of no consequence unless the cracks migrate to the next hole. Then your drilled discs are done. I think the drill/slots are for bling factor nothing else. If you bed proeprly there is no problem with pad imprinting and accelerated wear. I think 90% of problems are created by uninformed owners and improper bedding and disc break in. Today I don't think you can find any material difference between slots and solid discs. However, there is the markting and bling factor
It's near impossible to chamfer the inside holes on a vented disc. They may be doing a chemical deburr to help break the sharp edge, but I don't think they're getting in there with a chamfer and is why cracking continues to be a problem with drilled rotors. I would avoid them if you tend to do a lot of hard braking...the type you should really only be doing at a track. I've always like slots, rexrcr's explanation seems right and is in line with what I've been told by others.
Yes, there are performance differences, dependent upon application and operating environment. Street, no problem with drilled rotors, push the equipment harder, now one will have life and performance concerns. Drilled rotors will connect the dots in any application where the rotor's mass is undersized for the application and environment, which means all production based cars on a race track. Agreed, marketing and sales factor. Non-engineers / non-racers see drilled rotors as a desirable performance feature, not as the increased operating expense is truly is. Best regards, Rob Schermerhorn
Rob: I'm not disagreeing with you, but my experience is different. I went through 8 sets of brake pads of the previous stock F355 rotors in 31 track days. Othere than a plastic deformation under pressure, the surfaces were not gouged in any way by the pads*. *Other than the time I went through the pad material and was braking with the pad shells themselves.
