Drilled rotors

[lgee]

There was some discussion about drilling rotors making them weaker, well i was surprised today when we took the wheels off an Toyota Chaser V, and this is what i found, Toyota genuine discs  with 20 holes in them, and its not they are super thick either they are only 6mm thick in the center.

 

[Colby]

surely all the drilling is aftermarket workshop job?
Think about it though, its not really a great weight or inertia saver, those holes that close to the rotation centre would equate to sweet FA.

[SSS]

surely all the drilling is aftermarket workshop job?
Think about it though, its not really a great weight or inertia saver, those holes that close to the rotation centre would equate to sweet FA.

Bingo, and it's a rotary table on a mill type job to get it correct without throwing the rotors out of balance enough to make it a nuisance at 100km/h or over.

[lgee]

All 4 rotors were like this, i was very surprised.

[Jono]

I don't see how that kind of (re)drilling could significantly weaken the rotors. They're sandwiched to the hub face by the wheels! You can see the witness mark from the back of the wheel hub completely covers the holes.

However drilling the friction surface of most rotors can make them more susceptible to cracks from the heating and cooling cycles that they go through.