I track my car regularly and have had a problem for a while now with cracked rotors.... At first with Stoptech slotted discs the Pagid pads, and the pads would out wear the discs. That's with 3" brake ducts and stock Boss Brembos. So I switched to DBA 2pc T3 5000 rotors and am finding the same problem, just more expensive to replace...... Oddly enough the stock rotors had by far the longest life.... Just worn with no heat crackling... Still have them as spares. I generally use the rotors till my finger nails get caught on the crack.... Is this normal?? Or are the brakes saying time to upgrade? A set of new DBA rotor rings are half the price of the complete S550 15" setup, so its looking like a sensible upgrade..... more brakes for less long term costs. Or is this just a cooling issue and need 4" brake ducts?? Or just me??