Artwork by: Rebecca Zook
During this past summer, Moss Motors in California introduced a wood rimmed steering wheel for the Miata. This long awaited aftermarket option utilizes the factory airbag and is a direct replacement for the leather wrapped wheel that is standard equipment on many Miatas.
I first saw one of these wheels at the Miata '96 International Convention in Toronto. The Moss Motors wheel appears to be well made and is offered at a reasonable price, $250. However, I was not overwhelmed by its appearance. The standard black airbag in the center of the wheel seemed out of place next to the wood rim. This detracted from the look l hoped to achieve.
It was at this point that I began to investigate other options. Nardi and Momo both offer a selection of wood rimmed steering wheels in a variety of designs and diameters. I immediately found exactly what I wanted in Momo's "Grand Prix" offering. This 13.8" diameter wheel (slightly smaller than the Mazda factory wheel diameter of 14.2") is made of Italian Zebrano wood with thick brushed aluminum spokes at the three, six, and nine o'clock positions. The spokes have two rows of five holes each drilled for appearance. The horn button with the "Momo" logo is located in the center of the wheel (as it should be). Craftsmanship of the Momo wheel was flawless and the wood finish was not unlike a fine piece of furniture.
Be advised, the Nardi and Momo style of aftermarket steering wheels require removal of the standard driver-side airbag, should your car be so equipped. Although it may be legal for the auto owner to do this, we caution you to think long and hard before you remove the airbag. The authors of this article and the M Club do not advocate removal of your airbag. In anticipation of this modification, Drake has removed the factory slotted seat belt buckles and retrofitted new ones with a "gripper" bar inside. This type of buckle allows the lap portion of the belt to be cinched tightly at all times. Only the upper torso portion of the shoulder belt needs to be locked by the inertia reel. Thus there will be very little movement of the upper body towards the steering wheel if the car comes to a sudden stop.
Now that I knew the wheel I wanted, the next step was to determine the adapter hub that would fit the Momo wheel to the Miata. Since all U.S. Miatas come equipped with airbags (and it is currently still illegal for a dealer to disconnect the airbag), a Momo adapter kit for the Miata is not marketed in the States. Although most aftermarket vendors admitted there was an available adapter that would fit the Miata, all indicated they could not legally do the job. Also, none of the vendors would divulge which adapter kit was suitable for the Miata. A call to friend Andy Cork at Brain-Storm Products in Atlanta, however, revealed the answer: the adapter hub for the Mazda 323 would fit the Miata with minor modifications. A non-airbagged Miata will require the same adaptor.
Even after some heavy hinting to my long-suffering wife, Connie, it still was a surprise to find a Momo "Grand Prix" steering wheel and #5702 adapter hub under the tree on Christmas morning !
Now came the tricky part -- installation. I knew I was over my head so I contacted good friend/Miata guru Drake Daum who agreed to help with the conversion. Both Drake and I researched the project through service manuals and the Internet. On a cold, snowy Sunday afternoon in mid-January 1997 we tested the waters.
Before starting the installation, be sure to park the car with the front wheels straight and the steering wheel centered.
The first step is to disable the airbag. First, disconnect the negative battery lead (10mm nut). Next disconnect the clockspring connectors located below the steering column. These connectors are accessible by removing two Phillips head screws holding the access plate in place. The blue and orange clockspring connectors are interlocked. Disconnect the smaller orange connection before unplugging the blue connector. Drake and I found that it is almost impossible to disconnect the clockspring connectors unless you first pull back a black rubber boot that encases the rear portion of the plugs. This step is critical because the clockspring connectors isolate the airbag module from its back-up power source.
With the airbag disabled, it may now be disengaged from the steering wheel. Just remove the four 10mm attachment nuts, which are accessible at the back of the steering wheel. Disconnect two more connectors behind the airbag module (orange single-lead horn connector and a blue twin-lead airbag connector). Remove the airbag module and store it in a safe place.
Be extremely careful when handling the airbag module. Be sure to always carry the module with the face (trim) side pointing away from you. According to one of the ace mechanics at the Fairborn City Garage, the disconnected airbag module can be deployed by static electricity or the voltage from a standard AA battery ! Never use an ohmmeter to test the airbag leads for continuity. The voltage from the test leads may be enough to discharge the airbag.
Removal of the stock steering wheel is next. First, remove the steering wheel nut from the steering shaft using a 21mm socket and 6" extension. Have your helper hold the steering wheel in place while you break the nut free. Next, remove the steering wheel by utilizing a standard steering wheel puller. Trust us -- you WILL need a puller. (I borrowed one from a friend. You can buy one at Sears for about 20 dollars.) Attach the puller to the wheel with three metric bolts (8.0 x 1.25 x 25) by screwing them into existing holes in the steering wheel. Depending on the thickness of the puller used, it may be necessary to use some spacer washers on the metric bolts because the threaded holes are very shallow. The puller must be snugged down against the steering wheel structure before attempting to actually remove the wheel. Slowly begin turning the puller center shaft in a clockwise direction. The steering wheel will separate from the steering shaft with a bang, so don't be surprised ! The wheel will only move a fraction of an inch as the puller unseats it from the taper on the steering shaft. Carefully thread the blue and orange connectors out through the rectangular access hole in the steering wheel and remove the wheel.
With the steering wheel removed, you will now be looking at a yellow label on the clockspring cover and the electric pigtail encased in a plastic fixture located near the six o'clock position. This pigtail is the cable that terminates in the blue/orange connectors to the airbag and horn. Do not turn the clockspring assembly more than a few degrees from this position.
Now come the "minor modifications" needed to make the Momo #5702 hub fit your Miata. First, cut off the cable ty-wrap securing the pigtail to the clockspring strain relief. Then completely cut off the plastic strain relief from the riveted clockspring connector assembly. Using a Dremel cutting wheel or sharp X-acto knife, trim the outer edges of the riveted plastic connector to minimize its cross-sectional shape. Now cut off the stock blue/orange electrical connectors from the short pigtail as close to the connectors as possible. Be sure to note the green wire attached to the orange connector for the horn. Slide off the black cable sheath, shorten the sheath by about 1", and slide it back on the three wires. (Remember? One for the horn, two for the airbag.) Install a short length of shrink tubing over the sheath and slide it down over the reshaped plastic clockspring connector. Carefully heat the tubing to shrink it for a secure fit over the forward end of the sheath and the trimmed plastic connector. This sheath is necessary to avoid chafing the wires as they pass through the hub adapter.
Remove the brass contact ring assembly from the back of the adapter hub. It is seated in rubber and merely pops right off. This ring and its attached wire are not used in the Miata application. Locate the TOP of the adapter. Note the two small holes on the back side at the 6 and 12 o'clock positions. Centered below the 6 o'clock hole, and flush with the small lip immediately below the hole, draw a small rectangle. We machined out a relief area about 5/16" deep, about 5/16" high, and about 7/16" wide. This area is adjacent to a small hole already drilled through the hub by Momo. This existing hole is not used in the Miata application. The relief cut was started on a drill press and finished by hand with a Dremel tool. The hub material is relatively soft and easy to machine. Once the relief area is properly sized, we drilled a 3/8" pass-through hole in the top center of the relief area. Be very careful when drilling this hole. The hole exit is very close to one of the four hub support spokes on the front side. We also found it necessary to elongate this 3/8" hole with our Dremel tool. We further reshaped this hole into an ellipse coinciding with the long dimension of the relief cut (east-west). This relief cut and oval hole are necessary to accommodate the trimmed clockspring connector assembly which is riveted to the face of the clockspring connector cover plate surrounding the steering shaft.
Thread the electrical pigtail (without any end connectors) through the new pass-through hole in the adapter hub. Gently seat the hub adapter on the splines of the steering shaft, making sure the two points on the turn signal canceling sleeve (white nylon) engage the two holes in the back of the hub at the 12 and 6 o'clock positions. The trimmed clockspring connector should fit into the machined relief slot in the back of the hub. Check to be sure the hub turns freely on the steering shaft. Make sure the hub portion marked "Top" is in the 12 o'clock position. Finger-tighten the steering wheel nut on the shaft and attach the steering wheel and horn collar to the hub using the six Allen head screws supplied. Check that the steering column is not locked. If it is, when unlocked, the steering wheel may very well be off-center.
Before tightening the steering wheel nut to the specified torque, reconnect the battery and take a test drive around the block to make sure the steering wheel is straight. If not, return to the garage, remove the wheel, nut, and adjust as needed. Take another drive to confirm steering wheel placement before torquing the steering wheel nut to 29 - 36 lb.-ft.
Detach the steering wheel from the adapter hub. Thread the 3-wire pigtail through the access hole in one of the Momo hub support struts. Secure the electrical pigtail to the hub using a nylon ty-wrap. Next install the accordion-shaped, cosmetic rubber hub collar. Be sure to place the reference/index marks on the hub and collar at the 12 o'clock position. Now re-attach the horn collar and steering wheel and tighten screws.
Peel back a portion of the electrical pigtail threaded through the hub. The green wire is for the horn. The other two wires are for the now-absent airbag. Fasten these two wires together using a splice connector and stuff them back into the hub adapter cavity. Fasten a female spade connector to the green wire and attach to the male blade connector on the back of the horn assembly. Now center the horn button and gently press into place.
Reconnect the clockspring connectors below the steering column and replace the column access plate. Your Momo steering wheel installation is now complete !
Personally, of all the aftermarket modifications I've made to my Miata, I think I enjoy this one the most. It completely changes the interior of the car and makes the steering a little quicker, probably due to the smaller diameter wheel. The only drawback I've experienced thus far is a slight obscuring of the upper portions of some of the gauges (tach and speedo), again, due to the smaller diameter of the wheel.
The installation revolved around using an adapter for an '88 RX7. I pried off the brass ring and drilled and elongated one hole and connected it to the factory connectors. No cutting or splicing!!! Perfect location from the stalks!!!
Got the multimeter out and tested everything from wires to relays. It seems the problem with my horn was due to poor tolerances with the Momo Hub Adaptor #5702.
The brass ring that makes contact with the clockspring can have intermittent contact - you can check this by verifying that there is 12V at the clockspring and at the Momo wire to the positive terminal of the Momo horn button. It seems the inner plastic of the hub adaptor was not trimmed properly and the plastic would touch the clockspring instead of the brass portion of the ring. The Miata clockspring is VERY close to the center of the brass ring - you can tell by the wear marks.
This problem was intermittent because the plastic was fine on other portions of the ring thus only showing up depending on the position of the wheel! Once I trimmed the inner plastic all was fine!
That's one to keep in the back of your mind if you know of anyone having horn problems with a Non-Airbag (i.e. Canadian) Miata!
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07 April, 2001