Post 29: Heat Checking- When it’s time to replace your rotors

If you’re ever in the mall parking lot and see a stickered up car that looks like a track car… A peek at the brake rotors may be one way to tell if its legit or simply a “track inspired build”. Smooth, slotted or even drilled (oh my!) brake rotor designs are not an indication, but small cracks or “heat checking” may be. Track use is very hard on rotors. Some cars can crack cheap rotors after just a few days on track, but even light cars can cause “heat checking” on rotors.

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The heat checks on this slotted rotor are growing, but it still has some life left. 

 

If you start noticing tiny cracks on your rotors, you may immediately run to replace them, but wait! As long as you regularly inspect some specific parts of the cracks, you can run on them safely for quite a while.

Track Vocab Blank WM (1) (1)

 


When is it time to replace rotors?

  • Eventually those heat checks will get longer, wider, and deeper. The general guideline is once your fingernail can catch the edge of these cracks… It’s about time to replace.
  • Heat checking typically happens towards the middle of the rotor, if the cracks extend out to the edge of the rotor, then it is time to replace that rotor immediately.

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obviously, this is an extreme crack.

What can you do if you’re not sure how much life you have left?

If you are at all concerned with the condition of your rotors, pack spares. At some point, you will be replacing them; maybe next session, maybe next year. Carrying a spare set of front rotors may save you a big headache if you notice a bad crack between sessions at the track. Finding a replacement rotor near a racetrack on a weekend may be challenging and expensive.

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These are my Spec Miata rotors after a full season. There is some minor heat checking. They’re still usable. But at around $15 each, I replace them each spring.

Don’t worry… you won’t wear through your disc material on track: BUT, also checking in on the condition of the inside surface of the rotor is a good idea.

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