read that resurfacing the disc will result in reduced heat capacity. and it was recommended to never resurface the discs. while i can see how it makes sense, is the reduction in heat capacity really noticeable for all types of driving except maybe really competitive racing?

 

It's just a way to get you to buy more discs.

 

Technically having a rotor turned removes some material and so in theory should result in higher temps. But we're talking about a tiny amount of metal so it's alright to resurface as long as you don't exceed the minimum thickness allowed.

 

If you do any open tracking at all, you're better off sanding the disks with course grit sand paper before installing new pads. Don't resurface the brake rotors because you take off too much iron, which was what serves as the heat sink for converting kinetic energy of motion to heat energy (slowing your car). This is especially true if you open track your at speeds that put a smile on your face LOL

The thinner the rotor material, the less efficient the heat sinking, the quicker you'll go through brake pads and brake fluid.

FWIW, I go through new brake rotors (fr/rr) every two years open tracking (10-12 events per year) and daily driving my FD. Believe me J-spec rotors ('99 Type RS FD) are NOT cheap. Even through Mazdaspeed Motorsports Development they're $180 each (retail is $200+ each!)!

 

Rule of thumb for minimum brake rotor thickness is 90% of full thickness. For J-spec front brake rotors, that's ~29 mm (they start with 32 mm thickness). Use a thickness gauge, and run it across the brake rotor's swept area. If any place across the swept area, you encounter minimum thickness, the brake rotor is junk. Also if you have heat checks along the swept area, this also an indication of worn rotors. The heat checks will get deeper and deeper, and the brake rotor could shatter under heavy braking.