How-To: Rear Bumper Cut-Outs Miata MX5 Mazda

[artcentermiata]

Lets Cut Some Stuff Up!
http://i295.photobucket.com/albums/mm147/caboosage/DSCF1606.jpg
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2095.jpg

So, i get alot of requests on how i do these cutouts so clean. Figured its time to share the wealth!

First, here are the items i use to complete this proceedure
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2201.jpg

You'll need:
Jigsaw with fine tooth blade
Dremel with cut off disc and sanding drum
X-acto knife #11 blade
Sandpaper from 80-320grit
Some sort of flat plane items to use for sanding blocks (i used aluminum stock, the weight and rigidity make for fast level sanding)

And these, you can find at any art supply store
1ft (approximately) of 3mm mylar film paper
1/4 blueprinting tape (this is the best to use, because it is flexible, and has edging reinforcement that will hold a straight edge for big cuts) its available in many colors

First
Establish a center line in the bumper, this can be easily done by simply placing the tape in the middle of the plate area, and pulling it down over the bumper, and sealing it like so
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2208.jpg

Second
Here is where you can start trying out line cuts: starting the tape out on the centerline, you can pinpoint it with your finger, and the stretch it out to establish a straight line, once you have the length, slowly bring the tape down and then press with your other finger to seal the tape. Now you can work on the end curve by putting your finger on the starting point of where you want the curve to begin, and then slowly press it onto the bumper, following with your finger in the direction you want the tape to turn- basically, you are guiding the tape by drawing the line with your pointer finger.
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2211.jpg
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2213.jpg
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2209.jpg

Try different cuts before you decide
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2216.jpg

Third
Once you have decided on a cut line, we can now transfer over the curve to the adjacent side- This is where the mylar film comes into play.
Tape down the mylar over your curve, also fold over and tape down as many creases as you can- to keep an accurate transfer.
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2219.jpg

Now, Trace the curve with the draft tape
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2220.jpg
Follow your exact line

DONT FORGET to also trace the centerline so you know where to position the transfer once you flip it!
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2222.jpg

Here we have the flipped transfer, i lined it up by simply matching the traced centerline to the centerline on the bumper- Tape it down well on all angles, since you will be cutting it up- you dont want it to shift mid-cut!

Fourth
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2223.jpg
Now cut the centerline, this will give you a resting point once you start making the big main cuts

Simply start from one end- your choice: and cut away, following the line you made- Ive found the more streamline and quickly you cut, the better the cut comes out- going sluggishly tends to increase the waviness (its ok if its a bit' wavy, we can fix this later)
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2224.jpg
Notice the roughness of the cut, this is taken care of next!

Fifth
Now that we've cut, its time to clean up that jagged edge!
start with the heavy sandpaper and the largest/longest sanding block- run this back and forth in long streaks to level out the heavy waves on the cut, it could take a while to get it perfectly level- as your definition of perfection might be as high as mine. For the rounded edges, i switch to the smallest block (still with heavy sandpaper) and sand up and down the curve mixing with a horizontal movement (so, im sanding forward and back AND up and down simultaneously)- this will keep the curve true, but level the bumps.
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2226.jpg

Next you can use the smaller block with a mild sand paper to hit small trouble areas that just stand out a bit more after your heavy leveling work. Think of it as spot sanding
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2227.jpg

Finally, use the smallest block (choose something with a bit of flex; as this final step is only to smooth edging, not cut or remove) and something of 280-320 grit paper. Lightly sand the whole cut line to complete the leveling- and then angle the sanding block to smooth the edge (do this front and back to rid the bumper of any sharp or unsightly hardness)- This creates a "factory cut" finish.
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2229.jpg

Final Turnout
http://i295.photobucket.com/albums/mm147/caboosage/DSCF2238.jpg
There you have it, a nice smooth and even cut with soft edges that look like it popped right out of the mold that way!

I'll note that this bumper im having painted to match my car soon- hence the roughness and sanding marks everywhere.
This bumper cut proceedure can be done on any bumper, without affecting the paint or condition (just look at the top pictures of my car, those 2 cuts were made without any markings or trace of damage)

As you'll see in the above pictures of my car, i have painted my under-structure black to hide the ugly shapes and chassis tinks. You may also wish to do this to have the cleanest look!

Depending of the depth of you cut into your bumper, some crash reinforcement might show-
For NB guys, just paint yours black like i did to hide it
For NA guys, your support is a little lower down, you can simply cut the lower portion off with the jigsaw since it is plastic
Or remove that junk completely- i don't recommend that.

Good luck!

[WASABI]

Thank you. This is great to have on the site. Your pictures and descriptions make it look less difficult than I thought it would. Good work.

[kung fu jesus]

Bomb-ass writeup, Jeremy!

Thanks for doing this!

Note - Jeremy has done this on clean, unblemished bumper skins without damaging the surrounding paint. The one he used for this tutorial is one he planned to paint to match his car.

[psulja]

Great write-up, I've been playing with this idea on my NA. I really like the look but was always unsure of how to do it properly. Thanks for posting this!

[kung fu jesus]

The tape used has a few different names and there are different varieties.

You can use fine line tape, also called "draft tape":

http://www.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&field-keywords=draft+tape#/ref=nb_sb_noss_1?url=search-alias%3Daps&field-keywords=fine+line+tape&rh=i%3Aaps%2Ck%3Afine+line+tape

You could also use "chart tape":

https://www.google.com/search?sugexp=chrome,mod=4&ix=h9&sourceid=chrome&ie=UTF-8&q=chart+tape

Which is usually available at more office supply stores.

[diabeetus]

first off, this is a really bad ass write up and really great work man. you make it look so easy that maybe ill try it someday :fab:
another thing that might work as far as the tape goes is some 2 dollar pin-striping tape at advanced auto or the like. it comes in like 20-50 ft for a couple bucks.

[artcentermiata]

first off, this is a really bad ass write up and really great work man. you make it look so easy that maybe ill try it someday :fab:
another thing that might work as far as the tape goes is some 2 dollar pin-striping tape at advanced auto or the like. it comes in like 20-50 ft for a couple bucks.

The only problem with pin-striping tape is that it may not be able to bend into tight curve shapes, kinking or snapping could become an issue depending on your cut out line.

The drafting tape is made to conform and contour to most conditions

[Phatmiata]

this is a great write up! I still want to cut out the rear end on my Miata one of these days.

[Jayson]

Sending regards from Czech Republic :) Thanks!

http://imageshack.us/a/img832/4580/88455554.th.jpg (http://imageshack.us/photo/my-images/832/88455554.jpg/)http://imageshack.us/a/img341/5573/50982406.th.jpg (http://imageshack.us/photo/my-images/341/50982406.jpg/)http://imageshack.us/a/img35/3152/44262785.th.jpg (http://imageshack.us/photo/my-images/35/44262785.jpg/)

[HELLIONMX5]

What's the purpose again?

[RuckkehrMiata]

What's the purpose again?

It is a styling thing, similar to most mods you will find on this type of miata. In artcenter's case, he initially cut his bumper due to damage that was unappealing. Rather than a new bumper, he cut the damaged section off to create a new styling.

I would do it personally if I had the skill.

[Demon I Am]

Gives the bumper a different look, and can supposedly reduce some of the drag created by the bumper at speed.

I plan on doing mine sometime soon. Looks great, when done properly.

[kung fu jesus]

There is some debate about the rear bumper acting like a parachute. Some people cut the bumper for this reason, others for aesthetics. Jeremy does an excellent job of linking the styling curves to the modification and it look great. I may do this to my NB.

[iKhanh]

i plan on doing something like this in the future, but it would help if the pictures came back!

[kung fu jesus]

I am too. I watched Jeremy do a couple of these, but the pictorial is helpful.

I reached out to him to upload the images.

[artcentermiata]

They will be back soon, i had an issue with my upload account and lost them...

I plan on taking better pictures at our next tech day

[kung fu jesus]

:bow:

[Phatmiata]

soon the folks will start to riot!! hurry!!

http://affordablehousinginstitute.org/blogs/us/wp-content/uploads/frankenstein_villagers.jpg

[Flyin 92]

Oregonmon did a great job with his. I've been tempted to cut mine, but can't convince myself to like it enough to do it.

http://farm3.staticflickr.com/2865/11517789845_1ef5757f83_c.jpg

[kung fu jesus]

I plan to cut the bumper on my 10ae like Jeremy did the first go-around on his '99, pre-parking lot incident.

[Flyin 92]

If I had a center exit or dual RB I'd do it in a heartbeat.

[Demon I Am]

If you want to practice, I would like mine cut as well

[artcentermiata]

If people need a short reference until i take new pics... there are a few that survived in the first page of my build thread.

[charchri4]

Any luck putting the photos back?