Brake Discs, 1999 E300

Slotted and cross drilled allow for better cooling of the rotor and pads, reducing brake fade. Great for perfromance, and for safety.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

When the brake pad presses on the rotor it causes a layer of gas to build up between the two surfaces, reducing friction. Much like ice skates on ice.
Slotting or drilling the rotors allows the gas's to escape Allowing better surface to surface contact and better performance.

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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What's been mentioned thusfar is correct. IMHO slotted is far better for street use than crossdrilled, you get better gas dissipation from a slotted rotor due to the fact that the slots have two openings even when the pads make full contact on both sides, drilled just provides a temporary pressure relief until the holes clear the pads and allow the gas to vacate.

Asside from venting the real advantages for drilled are in weight reduction (for racing) every ounce of rotating mass shed is good. For hard repeated stop and go situations the loss of structural integrity can lead to warped rotors. Slotted suffers less in this regard. Best of all any rotor can be slotted by an average machine shop for little expense as compared to drilling which is far more complex and time consuming (expensive).

I've been slotting my brembos for years, also have the added advantage that if you slot the rotors to the corresponding depth of allowable rotor wear per side, then you have a clear visual cue of when your rotors need to be replaced, essentially when the rotor is worn flat to the bottom of the slot, time to replace

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Stable Mates:
1987 300TD 310K mi (Hans)
2008 Jeep Grand Cherokee OM642 165k mi (Benzrokee)