SL-C Manual: Hinges & Handles

At present, until a front hinge has been certified, the factory recommends against hinging the nose; the suggested mounting method is to use pins to mount the bodywork to the chassis as shown in the picture above.

Bolt the front shell to the splitter, along the edge of the front shell. This has the advantage of being very rigid, but somewhat more effort when access under the front shell is required.

The SL-C has had several different hinge designs for the tail, and the designs are different between the race tail and the street tail. Your hinge details may be different, but the overall concept of mounting should be the same.

The current hinge for the race tail uses a long aluminum piece that bolts to the flange on the tail under the taillight housings. This piece is then attached to the diffuser with a with a factory-supplied adapter. Although some builders have used gas springs to hold open the tail this is not recommended by the factory for either the street or race tail as the force from these units can warp the body.

You can fabricate your own rods to prop the tail open, or use thin cables to act as limiters so the tail doesn’t open more than is desired.
If you do elect to use gas springs, select ones with a very small pre-load, so that they mostly function as travel-limiters, not as an assist to opening the tail.

Door hinging is critical to making the SL-C have the superior body fitment for which it is known. If you selected the Body Fit option you can skip this section.

While not necessary, to improve access to the gas struts that hold the doors open, you may cut out most of the cup-shaped area of the body just above the struts. Fabricate small aluminum or stainless covers and attach them to tabs you left in the body when you cut out the cup-shaped area, or on the lip remaining from the cutout area. See the photo below for an example of this area, with a polished stainless cover made by the builder.

To remove the gas strut for servicing, lift the door to its fully open position. This will take the weight of the door off the gas strut. Remove the covers in the cup-shaped area for access. You will then be able to use a screwdriver to pry the metal release clip and remove the gas strut from the ball end. Rotate the gas strut assembly to undo it from the door hinge. 

The top aluminum door hinge is quite visible and can be surface treated to improve its appearance and ease of cleaning. Some builders have polished the hinges, and others have polished, then anodized or painted them. Clear anodizing looks great if you want to retain that polished aluminum look. Otherwise you can get them anodized or powder coated in the color of your choice. 

The door handles are from a Mazda Miata, and locks with keys can be obtained from a local Mazda dealer or wrecking yard if you want to implement them. The part numbers for the lock cylinders and keys are:

1997 Miata lock cylinders and keys:

• (left) N001-76-220E
• (right) NA01-76-210E

Most builders will not use the exterior lock part of the handles, and it is easy to put a cover plate over the lock. This has been done to the exterior door handle in the exterior photo below. If you do not implement the exterior locks, central electric locking is possible, allowing a way to secure the car as needed.

If you choose to not use electronic locking, you can modify the standard Miata handles to use a factory key for locking. To do this, you need to obtain a Miata lockset and key for each handle (part numbers listed above), and fabricate a bracket that makes use of the existing lock mechanism, as shown in the picture below (picture courtesy of Bill Phillips, who designed this modification):

Bill has also created a video describing the modification process that can be seen here.

Several builders have also implemented doors with solenoid-operated locks (i.e., “power door locks”) that use standard hot rod-style door solenoids to pull on the bear claw latches to open the doors. These can be controlled with aftermarket systems. 

If you use these solenoids, it is typical to also implement spring-loaded door poppers that push the door open slightly when unlocked so the door can be more easily opened by a person outside the car (as the exterior handles are usually removed and fiberglassed over when these power locks are implemented).

When mounting the exterior door handles, you will need to cut a slot out at the bottom of that handle recess in the body for the door handle actuator/lever. You can either leave the studs in or remove the studs and use bolts instead. Use large flat washers against the body where the handle mounts and secure the bolts with light duty thread locker or nylon lock nuts. Make sure you keep some form of spring mechanism on the handle to automatically pull the handle back flat against the body.

Note how the handle recess in the door is carefully cut out- don't just hog this opening out.

Following are pictures of the interior door handles mounted on the optional inner door panels (first picture) and builder-fabricated panels (second picture).

The interior door handles operate the door latch using a cable setup. This car has had an extension piece that has been added to the door handle so that it pulls the cable in the desired direction as shown in the photo below. There is an arrow pointing to the extension piece in the photo below. Note the aluminum bracket that this builder made to help locate the handle in the door.

The following photo shows the other end of the cable where it connects to the latch. There is a retainer bracket for the outer sheath that has been pop riveted to the builder-fabricated anti-intrusion bars that have been mounted in this car.

You will need to fabricate a bracket to secure the rear of the interior handle assembly to the interior door panel. The assembly is also secured by the front surround and the center mounting screw, but relying on the front plate alone is not recommended. The bracket can be affixed to the door panel using silicone adhesive or bonded using fiberglass or epoxy resin, or a similar technique. The cable is then fitted to the interior door handle assembly just prior to fitting the interior door panel to the door.

Anti-intrusion bars are a builder option, and can be made to reduce the impact of a side hit to the car in the door area, especially if you are not using the optional bolt-in side bars that are the norm for track day cars.