Free tool · 60 seconds
Resurface or replace?
Two numbers decide it: the minimum thickness your rotor's maker stamped on it, and what the rotor measures right now. Enter both and the math gives you a straight answer — before you spend hundreds on new rotors. Just been quoted new rotors? The two numbers are often right on the inspection sheet — a second opinion built on the shop's own measurements.
Measure the friction surface with a micrometer or caliper — not on the outer rust lip.
Cast or etched on the rotor hat or edge — look for “MIN TH” or “MIN” and a number.
Reading a shop's quote?
Dealer and chain-shop inspection sheets often list both numbers when rotors get quoted — look for “measured” or “actual” thickness next to the “minimum” or “discard” spec, usually per axle. If the sheet only shows pad thickness, ask for the rotor measurements — a shop that condemned the rotors has to have measured them. Type the numbers in exactly as written, and you've checked the quote against the shop's own micrometer. Bring the sheet in and we'll confirm on ours, free.
Where's the stamp?
Nearly every rotor carries its discard spec from the factory — cast into the hat (the center section around the studs) or etched on the outer edge. It reads like “MIN TH 28.4” or “MIN 28.4MM”. Can't find it under the rust? Your owner's manual or a quick search for your model's rotor spec has it — or email a photo to jdsrotors@gmail.com and we'll find it.
How do I measure without a micrometer?
A $20 caliper gets you close: measure the friction surface about 10 mm in from the outer edge, avoiding the unworn lip at the rim. Take readings at three or four spots around the rotor and use the smallest — rotors wear unevenly, and the thinnest point is the one that counts. One honest warning: jaws riding over ridges or scoring read on the thick side, so treat a caliper number as a best case — within a millimeter of the stamp, assume borderline. Or skip the tools entirely — bring the rotors in and our micrometer does it free.
Rotors still on the car?
You can usually read the stamp and take a rough measurement through the wheel spokes. For the real verdict, pull the rotors and bring them in — or call first and we'll talk you through it. We measure every rotor before any cut, and if the math says no, you pay nothing and we tell you exactly what to buy instead.
The verdict, the math behind it, and what it costs will appear here as you type.
This check is an estimate to help you decide, not a safety certification. The number stamped on your rotor governs, and the final call always comes from our micrometer — inspection is free. A rotor at or below its minimum should be replaced, not driven on.
No numbers? No tools?
Start with what you feel.
Three questions, no measurements. This won't diagnose your car from a web page — it tells you what your symptoms usually mean and whether resurfacing is likely on the table. Hands and a micrometer settle it.
Your read
Answer the first question and a straight read appears here.
Doing it yourself? Pull the rotors and bring them in — inspection is free. Using a shop for the brake job? Ask them to send the rotors to JD's — it's how our wholesale partners work every week.
For shops and service advisors
Run it at the counter. Ship us the rotors.
The measurements are already on your work order — put them in the checker with your customer. When the math says cut, send the rotors over and give your customer the option that keeps their OEM rotors: wholesale runs $20 to $35 a rotor, batches turn around same day, and pickup routes run for partners at 28 or more rotors a week. Mail-in works from anywhere in the Bay Area.
The why
What the minimum actually means.
Below minimum is not a suggestion
A rotor is a heat sink. As it thins it stores less heat, runs hotter, and flexes more — which means fade on long descents, a soft pedal, and in the worst case cracking. That's why the maker casts a discard thickness into every rotor: below that number the rotor is done, no matter how flat its surface looks.
The stamp also quietly protects your wallet in the other direction: most rotors reach the pads' end of life with material to spare. That margin is yours to use.
What one clean cut removes
Resurfacing takes off the wear pattern, the glaze, and the uneven pad deposits that cause pulsation — typically 0.2 to 0.5 mm total, about the thickness of a business card. We only cut when the rotor lands above its minimum with wear margin left for the life of the new pads.
Every rotor is measured before and after, and you get both numbers in writing next to the stamped spec. If a clean cut won't clear the bar, we refuse the job and say so. See the process.