Super Touring 6 Miata Extreme Weight Reduction Part 2

Getting the Super Touring 6 Miata down another 130 pounds is no simple task. In part 1, I laid out a plan of attack that I started at the most recent Nashville Superspeedway event. I brought my scales to document the weights, and although I may have looked like a maniac with a Sawzall in the paddock, the result so far is 55 pounds and counting. Here is the progress so far.

The Easy Items

Even in its current state, there are still a few ‘easy’ pounds to remove from the racecar. Starting with a weight of 1977 without a driver, I removed the wiper and wiper motor, along with the hardtop window gaskets and mounts. This was a quick and easy 7 pounds.

Of course, I kept the wiper motor assembly to go back in on a rainy day.

Starting weight for the extreme weight reduction on the super touring 6 miata. — *The starting weight on this journey is 1977 lbs. Removing the wipers, wiper motor, hardtop trim and brackets, and the windshield cowl.*

The take off pile during the extreme weight reduction of the na super touring 6 miata. — *Here is the take-off pile after ‘the easy stuff.’ It doesn’t look too impressive … yet. (Current weight 1970 or -7lbs)*

Removing Side-View Mirrors and Cutting the Doors

The following two areas would net 12 more pounds. First, the side view mirrors are pointless in the Miata and worth a couple of pounds each. I have roll cage-mounted side view mirrors that do a much better job of letting me see my blind spots. So out they go.

The NA Miata without side-view mirrors running in Super Touring 6. — *I like the look of the car without the side-view mirrors. Would this improve aerodynamics as well?*

I have very high and beefy door bars on the cage, so I removed the top support from the driver’s side. From the passenger’s side, I removed the quarter window, support, and top support. All it took was a quick session with the Sawzall.

The driver's side door of the NA Super Touring 6 Miata after gutting the doors further. — *Here is the result. I can be more aggressive and save an additional 2 pounds per door. However, I wanted to save that procedure for home in case I push things too far.*

Seat Belt Mounts and Trunk Firewall

Cutting the seatbelt mounts and the trunk firewall removed an additional 14 pounds. Once again, the Sawzall came out, as did my full complement of safety gear: a respirator and face shield.

Highlight of the seatbelt mounts to be removed from the NA Super Touring 6 Miata. — *Every pound adds up, and these seatbelt mounts are unnecessary with the roll cage.*

The NA Miata Super Touring 6 racecar with the rear trunk "firewall" removed. — *It’s not the best angle, but you can see most of the rear trunk “firewall” removed. (The passenger side seatbelt mount is still present in this picture.)*

Suited up with safety gear cutting metal off the NA Miata Super Touring 6 Racecar. — *A candid shot from my pit mates. I know they appreciated not only the noise I made but also the mess.*

Image 2 of the discard pile for the extreme weight reduction on the Super Touring 6 Miata (ST6) — *The discard pile is slowly growing—around 33 pounds now.*

Modifying Rear Bumper

I cut the lower edge of the rear bumper skin to improve aerodynamics. It opens at the bottom and acts as an air scoop, but in the wrong direction. I didn’t realize before starting, though, that mostly gutting the bumper would save significant weight—almost 11 pounds.

The rear bumper skin on the Miata that holds air at speed. — *The theory is that this area collects air at speed, and a little cutting will allow that air to exit easily.*

Marked areas to cut the bumper during the weight reduction process on the Miata. — *With the bumper removed, I cut the two marked extensions from the bumper mount and the metal wheel well.*

The trimmed rear bumper interior on the Super Touring 6 Miata. This was retained for structural support and bump drafting. — On my first pass, I removed the inner plastic support from the bumper, pushing this mod’s weight loss to 15 lbs. However, this left nothing to support the bumper skin for bump drafting, so I paired the support down to the center section and reinstalled it.

The final result from the gutted rear bumper on the NA Super Touring 6 Miata for weight reduction. — *The final result was 11 more lbs down. Even if it doesn’t improve airflow, the weight savings is worth it.*

One other note about modifying the rear bumper: This is another area in which I can be more aggressive with material removal, especially around the wheel wells. However, as this car had to pass tech and race the following day, I wanted to ensure I didn’t go too far. I suspect another 5-10 lbs from the surrounding areas, though.

The final iteration of the discard pile to remove weight from the NA Super Touring 6 Miata. — *The final discard pile sans rear glass. This is what 44 lbs looks like. (Popcorn for scale?)*

Hardtop Rear Window

The rear glass in the hardtop weighs another 11 lbs, bringing the grand total to 55 lbs. This is a relatively easy removal. Someone in the paddock claimed the glass was worth $500, so after removing the nuts from the inside, I used a heat gun and gently pried the glass off. I also managed to get it home in one piece.

The NA Super Touring 6 Miata with the rear hatch glass removed. — *Easy 11 lbs, and I have a piece of Lexan ready to go in if I decide the window is necessary.*

There is a conflicting opinion on how the rear glass affects performance. I will discuss that next time. (Link incoming.) Occam’s Racer has a good article on the subject, but it is geared towards cars running wings and splitters. When dealing solely with mechanical grip, the story is a bit different.

More Weight Reduction Opportunites

That is it for this installment, but it is not the end of this process. I am trying to get as much weight (at least another 50 lbs) off of the Super Touring 6 Miata as inexpensive as possible. There are at least 20 more lbs through creative trimming, and I was shocked that the rear trunk is 30 lbs. I plan to shave another 50 off the car by focusing on these areas. And with around 20 lbs in driver adjustment, the ST6 Miata will be at the pointy end of its capability in the power-to-weight department.