That is a very good question, and one that is easily answered !
The differences between the 1879 FZR and the Power Slot 126.42090CSR are primarily in the 'slotting configurations' You'll notice that the 1879 FZR has a "5x3" slotting pattern, while the 126.42090CSR , has 6 individual slots cut around the circumference of the rotor.
The 1879 FZR starts life as an 'ULTRA PREMIUM' rotor on it's own merit. That is to say, that it's a bit heavier in weight,and thickness.
We have designed the and 'branded' the 5x3 slotting pattern for the purpose of providing the most effective way of slotting, with out taking away from the 'mass' of the rotor. It has also proven to be a bit quieter during operation and ads to the cooling effect associated with slotting. Slotted rotors in general, provide better stopping characteristics in a wet environment, by channeling water off of the pad/rotor interface, providing immediate contact between the pad and rotor surfaces. The slots also serve as a 'wiper slot' constantly cleaning the face of the pad with each wheel and rotor with each rotation.
The most popular choice has been the 1879 FZR SL/SR rotors for the front and 1712 FZR SL/SR for the rears, combined with Hawk 'LTS' Light truck SUV pads.
Hope this helps.
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