Hi all, I've found myself in a situation where I'm doing a manual swap on an FD. As luck would have it, I had most of the parts left over from another build I've done, except one thing, the clutch pedal assembly. I didn't think much of it at first given how common manual cars are, but much to my surprise LHD clutch pedal assemblies are being sold for a premium. I'm not one to pay the FD tax unless I have to, so I started my search for alternatives and found that RHD assemblies can be used, but they need modification, and they ALSO are quite pricey. Here's a nice write up if you happen to be interested in that route, but for those of us who are handy I'd like to propose a different option that's less labor intensive, and a fraction of the price. Enter the 1990-2005 Miata clutch pedal assembly. At the time of writing this, you can get these assemblies off ebay, with the clutch switch and the starter interlock switch for about $80 shipped. so lets get started.

What you will need:
- hand drill with drill bits. I used one of those step drills for everything and it worked like a champ.
- die grinder/air grinder/Dremel tool. Just something you can grind away metal. if your very patient hand files would likely do.
- tape measure
- sharpie marker
- a few pieces of common hardware, so washers and whatnot that can be found at any hardware store.
- bench vise (preferred but not really needed)

that's it. You'll notice a welder is not on the list of tools you need! So lets take a look at the Miata assembly. I had already removed the starter interlock switch, but it mounts to the 2 studs in the next picture.




For those who have seem a rx7 pedal assembly, you'll notice to resemblance. One major difference is that the Miata assembly has studs on the back, where as the rx7 the studs are on the clutch master cylinder. For reference, the stud pattern is almost the exact same. The little plate I'm holding, is the firewall block off plate from the FD.


So lets get to it.

STEP 1:
remove the locating bosses. The two bosses on the backside of the assembly are spot welded in 4 places each. Take a grinder and grind out those stop welds and they should come right off leaving you with the exposed threaded stud. The spot weld locations are quite easy to spot and look like little indentations at the base. Here's a picture of one removed and the other with the welds ground out:


STEP 2:
Remove the threaded studs. These are a little more time consuming, but not hard. One of the studs had some fairly substantial welds holding it in, the other, twords the center of the assembly, has 3 spot welds holding it in place. Here's the removed studs, you can see the remnants of the welds on both.


STEP 3:
Drill those holes the studs were just in out to .50in. This takes care of that slight misalignment between the mounting patterns.




STEP 4:
Drill out this hole to .625-.75in ish...This is for clearance around a threaded stud that's on the firewall so it doesn't need to be perfect, and in later pictures you'll see I actually drill out hte hole next to it and ended up grinding all the way over to this hole make it fit. So you may need to play with this opening a little, but this should get you darn close.


STEP 5:
We need to make a little clearance for the firewall, so we need to cut back some of the top side of the bracket. cut out the little web at the tip of the bracket (shown at the right side of the next image). I'm not 100% you need to do this, but it will make installation easier. In addition to that, about 3.25inches from the backside of the bracket draw a line across the top of the bracket.


from that line draw a 45 degree line on the sides facing the rear of the assembly and a straight line from the little notch at the back of the bracket and cut that area out. When you're done it should look something like this. Also note the 3.25" is measured from the back of the bracket like this:

 

STEP 6:
If you still have the pedal assembled you'll notice that the area we just cut out was used to support the return spring. So we need to add something to support that. I mounted a bolt thru the bracket, and just used the spring to locate it. Doesn't need to be overly accurate as long as it captures the spring end. This picture again for reference.


We're almost done already!

STEP 7:
modify the clutch pedal arm. Here's the stock FD clutch arrangement from my R1:


Here's the Miata assembly with the modifications we've done so far mounted up:




As you can see the whole pedal need to move over about 2 inches. I solved this by squeezing the bends in the arm straight in my vice


Stock dimensions of the arm before modification for reference:


and after straightening, it's within 1/8inch of the stock location.


STEP 8:
This is the last one! The pushrod need to get chopped down to 2.53-ish inches


STEP 9:
installation. Nothing overly complex about mounting. You will need some washers behind the nuts as you will bottom out the nut before it gets tight. I have a lathe so I made a standoff which you can see in this next picture. The only other thing is you may need a larger fender washer for the top nut. You can see I did that here as well.


and here's the stud on the firewall we drilled clearnace for earlier:


That's it! It interacts with the stock FD master cylinder like the stock assembly. The only other thing that will need to be addressed, it really the brake pedal as it's quite a bit different than the manual pedal. If you have a welder, welding in the fender washer would be ideal, and chopping the pedal arm length and bringing the pedal up to be in alignment with the brake pedal again would be great, but it certainly works as-is. I'll likely do this and I'll update this thread accordingly once it's done.

 

Nice! Great alternative!

Are you able to get the stock clutch switch working with this setup?

Dale

 

Miata uses the same one(s). failure rate is higher, cause "The Blue Thing"

 

YES! and in fact the connectors for both the clutch switch and the starter interlock switch look to be plug and play to the FD manual harness. So if for whatever reason someone was replacing a broken clutch assembly in an original manual car, the harness should just plug right in to the Miata sensors. Here are the Miata sensor plugs.


I do not know if the FD and Miata sensors are physically swappable if that's what you were asking.

As far as wiring the sensors into an auto car, the clutch inhibitor switch should be wired into the L/Y and R/Y (on the emissions/engine harness side) wires on the X-05 connector. They are beefy and hard to miss!

The clutch switch get wired to a ground point for 1 wire, the other should go to the G/W (on the emissions/engine harness side) wire on the X-05 connector. It will also need to go to pin G (L/W on auto cars) on the Q-01 cruise control unit if using cruise control. I'll need to double check, but I think the cruse wire is spliced off before the X-05 connector anyways, so one shouldn't need to run a separate wire to it. I'll double check with the meter later.

 

they literally use the same ones.