By Aaron Tachibana
Remove the stock steering wheel per the fantastic instructions one can find on miata.net. Do a search on air bag removal..and follow the instructions..very simple and well detailed. Once you have removed the old steering wheel and air bag...stop...do not throw anything away. I have come across a few people that have followed some of the netter's instructions on installing the Momo wheel which tells them to discard the clock spring connector. Repeat...do not throw anything away...you will be modifying the existing parts...nothing dramatic..but usage of the stock parts are imperative..Mazda does not sell the individual components in the steering column...you have to buy them all in a complete kit. This is expensive, and not necessary if you follow my instructions.
Some install comments...tools required:
21mm socket and 1/2" drive ratchet
1/2" drill bit and drill
Philips screw driver
10mm socket & ¼ ratchet and extension
Dremel tool with grinder cone
3ohm ¼w resistor
MOMO hub adapter #5702
Once the wheel is removed you will see the clock spring connector. Remove the four screws (could be three, can't recall here). Lift out the clock spring. You will now expose the turn signal canceling device. This is a white plastic thing that has two opposing locator pins at 12 and 6 o'clock positions. Take a permanent felt tip marker and place a mark on the side (mark right or left so you'll know how which way to put it back in). This is so you will know what orientation when reinstalling install it.
Take out the clock spring connector. You'll notice that there is a three wire lead and a large multi-connector attached. On the end where the large multi-connector is, cut it off with a pair of wire snips. You will not need the multi-connector portion, but you will need to utilize the wires. Next on the end of the wires that attaches to the clock spring connector, there is a rectangular black connector surrounding the wires and is attached to the clock spring connector with two very small brass rivets. Here's where one needs to be careful. Using a small saw (I used a fine toothed coping saw), gently cut the outer casing off of the connector cutting as close to the clock spring connector body as possible. Cut very slowly and not too deep. An approximate 1/16" should do it. There is an inner connector inside the housing that you do not want to cut into. Be careful to not cut into or cut through this portion of the connector. You are merely trying to remove the outer connector casing so you can reduce the physical size of the connector because you are going to place this connector through a hole in the hub adapter. After you cut the outer connector housing off you will expose the inner black wire connector housing and three wires protruding from the clock spring connector. Wrap a small piece of electrical tape around the housing and wires. Keep it tight and wrapped small, remember the reason you cut off the outer connector housing was to make the connector as small as possible without jeopardizing structural rigidity.
Now take the clock spring connector and mount it back over the white plastic turn signal canceler. Press down hard on the clock spring connector so that it is compressed all the way against the turn signal canceled. Now take the felt tip marker and scribe a line on both of the turn signal canceler tabs that the clock spring connector fits over. Mark the line on the inside of the turn signal tabs, closest to the clock spring connector. Now remove the clock spring connector.
After removing the clock spring connector you'll see the exposed white plastic cone thingy turn signal canceller. This is pressed fit into the steering column. Grab it with your fingers and pull out gently. It should just pop out. now you know why you marked the orientation of the turn signal canceller.
Take a Dremel tool grinder and carefully grind an approximate 1/4" notch below the scribed felt tip marks you have made on the turn signal canceller. Be careful not too grind the tab off or go all the way through. you want to grind just enough on both of the clock spring connector mounting tabs on the turn signal canceller so when you reinstall the turn signal canceller the clock spring connector will now rotate completely 360 degrees around the turn signal canceller. This is very important. you may have to fit and refit the assembly to get the correct notch clearance between the turn signal mounting tabs and the clock spring. It sounds difficult, but when you have the items in hand you'll understand what clearance is required.
Once all has been done, reassemble the unit. put the turn signal canceller in (it just snaps into place...remember the mark you made indicating the original orientation). Follow the instructions on the clock spring connector as to how to orient the internal spring. It's self explanatory, and written in black lettering over a yellow background on the clock spring connector itself. Secure the clock spring connector to the steering assembly.
Now comes the modification of the hub adapter. Realizing that there are several adapters that people have been using for Miata's..I have chosen the one that Momo has in their catalog. It's part number #5702.I use this adapter because it is much easier to modify than the 323 adapter that some people use. Take the hub adapter and turn it over. you will notice that there is a brass and black plastic ring around the bottom opening. Simply pry this ring off and discard it. You will now notice a approximate 1/4" hole in the five o'clock position on the hub. take a 1/2" drill bit and drill out the hole. Once you have done this chamfer the hole so that it is slightly out of round..a little oval works well. using this methodology removes the necessary amount of metal so that the connector can go through, yet leaves as much of the hub adapter base as possible for structural rigidity. This is the hole that the wire connector from the clock spring connector is going to protrude from. Now you understand why you removed the outer connector on the clock spring connector wires.
Feed the wires from the clock spring connector through the hole in the hub adapter, and mount the adapter to the steering column. It may take a couple of tries as there are the two locator pins sticking up from the turn signal canceller that you need to insert into the bottom of the hub adapter. Careful...do not use brute force. the splines on the hub adapter and the steering column are fine thread, and it takes patience to line everything up right. Once you've got the adapter on take the green and orange (I think?) wire (this is the power lead for your horn) and attach an electrical slip couple to the end of the wire. Then attach it to the horn button. The other two wires attach together. this completes the air bag circuit...
Now assemble whatever Momo steering wheel you have following the manufacturers instructions. Oh yeah..the air bag light will keep blinking unless you place a 3ohm ¼w resistor in the wiring harness. (Follow the instructions from racerX's Momo posting on the miata.net)
There you have it. It was important that the install look factory along with functionality and operate safely. Using my methodology gets these things accomplished...
Also..I used the Momo Competition model steering wheel. It is 350mm, the stock Miata wheel is 365mm. The only problem with the 350mm is you will obstruct the top of the tach and speedo...but the important redline is very visible. Also the steering wheel sit rather close to the turn signal stalks..I have small slender hands and it doesn't bother me, but if the wheel is too close..use the Momo steering wheel spacer kit from them. It will bring the wheel out approximately one inch more.