Listing of Underchassis Bolts and Their Torque Requirements
For the Mazda Miata
By: Joey Bernardez

In the interest of maintaining our adored toys, I have taken the time to compile this list of assorted bolts and nuts along with their torque specifications from the Miata Workshop Manual. With it I, also share with you the experience that Jason Cuadra and I encountered as we executed the procedure, so that the others who will engage in it in the future will be able to completely and expeditiously perform the same.

It was suggested prior to the execution of this procedure to use the drive-up-lift rather than the chassis-lift. However, using the drive-up-lift prohibits access to some bolts underneath the car. Hence, we had to use the chassis-lift.

The procedure was executed at Midas on Buendia Ave. and costed Php 500.00.

Jason and I employed different procedures for our respective cars. On mine, we first loosened the bolts and then tightened them to the specified torque requirement. This was done to make sure that the bolts weren’t just stuck. Because my car was first and we were still new at the task, it took us 3 hours to finish the job on my car. Another down side was that we couldn’ttell which bolts had loosened up because we loosened them up before tightening them.

On Jason’s car, as he was pressed for time, he opted to just tighten them without loosening them. With this procedure we could determine which bolts had loosened, moreover, it was much faster. However, we couldn’t determine if some of the bolts were just stuck and as such they were already tight.

It is the reader’s option which procedure to follow.

According to Jason, there’re are some bolts here that are notorious for loosening, these are: the bolts on the Lower Suspension Arms. Such being the case he suggests to tighten them to the maximum specified torque. On all others we targeted the median point on the specified range.

We also noticed that on some bolts the Enthusiast’s Manual has higher maximum torque specs. Which to observe is a matter of choice.

The torque specifications mentioned herein are measured in ft-lbf.

Engine Mounts:
At the bottom of the engine, on either side thereof, are 2 circular depressions with a nut on the center, these are the Engine Mount Nuts. They are to be tightened to 42-57.

Power Plant Frame (PPF):
Connecting the transmission to the differential, beside the drive shaft, is an aluminum beam called the PPF. There’re 7 bolts on here, 2 on each end (4) which all need to be tightened to 77-91. There’re three on the middle of the beam, 1 big and 2 smaller ones. The big one’s to be tightened to 76.7-91.1, while the two smaller ones are to be tightened to 27-39.

Propeller Shaft:
At the end of the propeller shaft connecting it to the differential are 4 bolts. Tighten these to 37-43.

Differential:
The differential is mounted to the Rear Crossmember at 2 points Each point with 3 bolts, 1 big one at the center and two smaller ones at the side. Tighten the big one to 62-72, and the smaller ones 14-19.

Rear Crossmember:
The rear crossmember is attached to the chassis with 6 bolts (note that the ‘96 Workshop Manual only has 4 bolts securing the rear crossmember to the chassis). 3 on each side located over the upper suspension arm. These are to be tightened to 69-86.

Rear Stabilizer Bar:
The Rear Stabilizer Bar is attached to the rear crossmember with 4 bolts, 2 on each side. These bolts are to be tightened to 15-20. Attached to the ends of the rear stabilizer bar are control links to the knuckle. The control links each have 2 bolts at the ends thereof. These are to be tightened to 27-39.

Upper Arm:
The upper arm has 3 bolts, 2 on the crossmember side and 1 on the knuckle side. All 3 are to be tightened to 34-49.

Lower Arm:
The lower arm has three bolts, 2 on the crossmember side and 1 on the knuckle side. The 2 on the crossmember side are to be tightened to 54-70. The one on the knuckle side is to be torqued to 47-54.

Shock Absorber:
The shock absorber has 3 mounting bolts, 2 on top 1 at the bottom. The 2 on top are to be tightened to 22-26, while the one
on the bottom is to be tightened to 54-68.

Front Crossmember:
The front crossmember is attached to the chassis with 8 bolts, 4 on either side. On each side, 2 are above the upper arm and the other 2 are beside the transmission. The 2 beside the transmission are to be tightened to 51-61. While the 2 over the upper arm are to be tightened to 69-86.

Front Stabilizer Bar:
The front stabilizer bar is attached to the crossmember with 4 bolts, 2 on each side. All are to be tightened to 14-19. At either end of the bar is attached a control link. The control link has 1 bolt on each end (it therefore has 2), these are to be tightened to 27-39.

Upper Arm:
The upper arm has one big bolt on the crossmember side which is to be tightened to 87-101. On the knuckle side is the upper ball joint, the bolt of which has a cotter pin and thus does not need tightening.

Lower Arm:
The lower arm has 3 bolts, 2 on the crossmember side, the one at the front is to be tightened to 69-83, while the one at the rear is to be tightened to 62-75. On the knuckle side there’s 1 bolt which is to be tightened to 47-54.

Shock Absorber:
The shock absorber is mounted at 3 points, 2 on top which need to be tightened to 22-26, while the 1 at the bottom needs to
be tightened to 54-68.

Shocktower Brace:
We torqued this to 30 (Jason specified).

It must be noted that: there are other bolts that have not been mentioned inasmuch as they have cotter pins on them and thus should not require tightening as the cotter pins prevent movement of the nut; also there are bolts that are mentioned in the Workshop Manual but cannot be accessed without disassembly of other parts, such as the steering rack bolts and the bolts for the lower seat of the lower ball joints, thus we did not bother with them.

In my opinion, the effects of the procedure are not significant, i.e., the tight feeling of a new car which I expected was not restored. My car had around 13,000 km when I performed this procedure and most if not all the bolts were still rather tight notwithstanding the punishment that it receives as a daily driver and the thrashing it was subjected to at the Subic racetrack and skidpad.

Nonetheless it does give one peace of mind.

I hope this will be of help to all the other enthusiasts who’ve been complaining of looseness. Good luck!

*Thanks to Allan Lavarro for lending me his Workshop Manual!