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Old 03-26-2003, 11:19 AM
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csnow csnow is offline
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Join Date: May 2002
Location: Mass
Posts: 1,127
I've had poor results with cross-drilled rotors.
Perhaps it's the roadsalt and gravel in my climate.

My theory is that the abrasive road grime collects in the holes and gets trapped in the works instead of being swept away.
This trapped debris digs deep gouges in the rotor face and pads.
The chamfered holes may even encourage this to some extent. Many of the holes were completely clogged with debris. These ran about 1.5 years/22k miles to get this bad.

Looking at the pic, note that only the outer 1/4 inch or so of diameter (where there are no holes) is still in contact with the pads. The swept area that has holes has worn away so badly that there is no contact between pad and rotor.
The pads would otherwise have been about half-worn.

These are Brembo rotors with carbon-fibre pads on a modern Jeep. I'm currently running slotted rotors on both my Jeep and my MB for comparison.
Attached Thumbnails
Zimmerman Cross-Drilled Brake Rotors-1pad15k.jpg  
1986 300E 5-Speed 240k mi.
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