How to: Miata Bumper Cut
If you’re reading this, you’ve probably heard that your Miata’s rear bumper acts as a parachute. This can slow you down, increase lift, and reduce gas mileage. However, for most Miata owners these issues are hardly noticeable, and this mod will mostly be for aesthetics.
The size of the cut will also make a difference, but because I primarily drive my car on the street, my cut is designed to be simple, clean, and provide enough space for a rear diffuser. If you look around at the serious race Miata’s, you’ll find that most people just remove the rear bumper entirely for maximum efficiency.
To get started, make sure your car is parked on a flat and even surface. This will make the measuring much simpler.
- Cutting wheel
- Drum sander tips
- Masking/Painters Tape
- Measuring Tape
- Phillips Head Screw Driver
- Ratchet w/ 12mm socket
Step 1: Design your cut template
The goal of this step is to match the cut on the driver side of the car with the exhaust cut on the passenger side. My approach was to line up a sheet of paper with the outside edge of the bumper, then trace a line around the bottom of the bumper and around the cut out for the exhaust.
Step 2: Lay the cut template on the drivers side
Use some masking tape to hold the template on the bumper. Try to use a few different reference points to measure from, just to make sure it's sitting perfect. I measured from the ground to the top of the cut out, and from the side of the bumper to the start of my first cut.
Step 3: Mark the bumper for a cut line
Using that measurement in the last step(ground to the top of the cut out), Mark the bumped all the way across in at least 5 places as a reference point.
Step 4: Lay masking tape for cut
Using your reference marks, lay the masking tape all the way across the bumper. The tape should sit directly on top of all of your marks. It will match up with the exhaust cut out, and your cut template on the drivers side.
Stand back and look at the line, it should be even and level. Adjust if needed.
Step 5: Cut the bumper cover
Time for the fun part! Using your Dremel and cut wheel, simply follow your cut line across the bumper.