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Originally Posted by dynodon
A few points from someone that has run a lot of differnt disks.
1. Slots and drilled holes have the same possibility of stress cracks. Chamfering the holes helps.
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Not true. Drilled rotors develop cracks under racing conditions sooner than plain or slotted. On the street, quality drilled rotors are no more prone to cracking than plain rotors. This is a racing problem, not a street problem. Of course, if you buy your drilled rotors on eBay, you're getting Chinese counterfeits that have been made in boutique foundaries with no process control, poor casting quality, and not even heat treated. In that case, the drilled rotors may crack even on the street. But if you stick with reputable brands from reliable retailers (e.g., Tire Rack), you won't have a problem.
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2. A better way is to have grooves that don't go all the way through, less chance of a stress crack.
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This doesn't make sense, unless you are referring to "dimpled" rotors. The word "grooves" is usually used interchangably with "slotted" and the slots are never cut more than 1mm deep into the rotor face and thus never go all the way through. You must mean dimpled instead of drilled here.
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3. There is NO extra "wear" due to holes or slots, they don't dig into the pads or wear them more than usual.
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Again, not true. You pay a slight penalty in pad life when you go with slotted rotors and a greater penalty with drilled. In either case, the difference is not dramatic, but it is there.
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4. Most racers do not use slotted or drilled disks because more mass is better for brakes, and under extreme use, a solid disk is better, less likely to come apart. Check the real race cars including NASCAR where they put about as much abuse as possible, and you won't see slots or holes.
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Where are you getting this information? Virtually ALL the racers in SPEED World Challenge and Grand AM Cup (where I hang out) use slotted rotors. Occasionally someone will risk running drilled rotors in a qualifying session to take advantage of the weight savings (about 1/4 pound per rotor) to get a better starting position on the grid, but then will usually switch back to slotted before the race starts for fear the drilled rotors will crack before the end of the race.
I'm not active in NASCAR, so I contacted Essex Racing, the master distributor for AP and supplier to many of the top teams in that venue. They tell me that
all of the top teams in Winston Cup, NASCAR Truck, and Bush Grand National run slotted rotors with the exception of one or two back markers.
Whoever is feeding you the information you posted does not know what they are talking about and I suggest you look elsewhere for your brake advice.
