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Old 12-22-2011, 06:38 PM   #1
lupinsea
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Join Date: Sep 2005
Carmudgeonly Ride: Modified Jeep Tj and '07 Miata
Location: Seattle
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First NC MX-5 Mod - Throttle Pedal Adjustment

I posted this over at Miata.net, figured I'd repost here.

The clutch and throttle pedals on the NC are a bit wonky. Lots of guys over at Miata.net have brought up the complaint. Turns out either the clutch is a bit too far away or the throttle is too close. It can make for some uncomfortable long-term driving.

This morning I did the adjustments on both pedals and I can say it's a marked improvement. Cost is free if you discount the chiropractic bills after contorting oneself to get under the Miata's dash. Ooof. Time is about 15 min if you're not taking picture to do a write-up.

For such a simple mod I normally wouldn't have bothered with my own write- up but . . . the write-ups on Miata.net suck ass. Generally good an helpful but it's like people haven't heard of a digital camera over there. So all text and little-to-no photos to show what's going on.


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THROTTLE PEDAL ADJUSTMENT

While this topic has been covered numerous times before I thought it helpful to do a start-to-finish write-up with some clear photos and instructions.


Issue
Throttle pedal location is too close to the driver vs. clutch pedal. Either the right foot is at an odd angle on the throttle to make the left foot comfortable on the clutch, or the left foot needs to over extend so the right foot can be comfortable on the throttle. In either case, it can be a less-than-comfortable pedal arrangement.


Solution
Adjust the throttle and clutch pedal positions to find a comfortable balance. In the case of the throttle pedal, stacking washers between the firewall and throttle assembly at the upper mounting bolt will pivot the pedal down and toward the firewall, away from the driver.

Note 1: this write-up only covers the Throttle Pedal Adjustment. See the Adjusting The Clutch thread for clutch pedal adjustments.

Note 2: Some minor adjustment of the throttle pedal won't adversely affect the heel-toe relationship between the throttle and brake. After stacking 3 washers under the top bolt I actually noticed an improvement in this relationship. Since this mod isn't permanent and can be reversed, feel free to experiment with the number of washers.


Procedure
The general procedure involves removing the throttle assembly, taping on some washers, and then reinstalling the throttle. The single biggest headache of the mod is getting into a comfortable working condition under the dash. The easiest for me: sitting upside down in the driver's seat, sometimes with my legs in the passenger seat. Fun times. But, this doesn't take long, maybe 15 minutes or less if you have everything ready to go.

Gather Tools and Parts:
First, gather the tools and parts needed for this mod. Some washers, a 10mm wrench, some kind of 10mm socket and extension, and some tape.

The stock bolts are 6mm 1.0 x 25mm long metric fasteners. These will accept about 5/16" (~8mm) worth of stacked washers and still have sufficient thread engagement. If you want more washers for further pedal adjustment you'll need a longer bolt, try a 30mm or 35mm length.


Supplies needed.


Remove Throttle Pedal Assembly:
The easiest way to tackle this project is to simply remove the entire throttle assembly. This way the washers can be taped on and installed without having to fight the top bolt in a very cramped and uncomfortable working condition.

First, pinch the wiring connector at the top of the throttle assemble to release it's locking tabs and wiggle it off. Tuck it out of the way up under the dash some place.

Next, there are two bolts attaching the throttle assembly to the fire wall. You'll need the 10mm wrench to loosen these. Because of the awkward location of the upper bolt way up under the dash, a 10mm socket and extension is helpful to turn the bolt since it'll be tough to get your fingers on it.


Remove connector and the two bolt to take out the pedal assembly.


Stacking Washers:
Once the pedal assembly is removed you can see that the ratio between the bolt holes and the middle of the pedal are more or less the same. This means that however many washers are stacked under the top bolt is about the same distance the pedal is moved further away from the driver's seat.

This is a game of less than inches. It doesn't take a whole lot of washers to get a vastly improved pedal location. With only 3 washers (~5/16" worth of a stack) I already noticed a big difference.

Ideally, 1/4" fender washers would be used as they will fit a 6mm bolt and are wide, to provide good bearing for the plastic throttle assembly. However, I used sufficiently wide cut washers I had laying around the house and they did the trick. Do note that you don't need washers or spacers to cover the entire base of the upper throttle assembly as there is a shoulder on the mounting surface. The washers only need extend to the shoulder. Anything beyond this offers no extra support.

Also, if you are reusing the stock bolt make sure you have about 5/16" (~8mm) worth of thread engagement left. If you want a thicker washer stack then get a longer bolt before you start.


Note: the ratio between the bolt holes and middle of pedal is about the same.



Left: The shoulder under the top mounting location. Right: 3 stacked
washers on the stock bolt leave just enough threads for good
engagement on the firewall nut.


Taping Washers:
Given the tight confines under the dash, it's easiest to just use some tape and secure the washers to the throttle assembly before installation. The tape won't throw off the pedal and make it wobble, and you won't be fighting to keep the washers on the top bolt as you try to reinstall the throttle assembly.


Taping the washers on makes re-installation so much easier.


Reinstall Throttle Pedal Assembly:
With the washers taped in place, reinstall the pedal assembly, starting with the top bolt. Once the two bolts are in and snugged tight then reconnect the wire connector at the top of the assembly.

That's it!

I left the tap on since nobody will see it and it doesn't affect anything. However, I suppose if one wanted they could try and rip it out of there after the top bolt catches a few threads.


Throttle assembly reinstalled with the washer stack at the top.


Bonus:
While your under there, don't forget a 12mm wrench so you can adjust the clutch, too. See the Clutch Adjustmenth thread for further details.


Resources
Thanks to the Miata.net NC nuts around here for the idea. Lots of handy and helpful reading on this board. And especially for Sloopercat's thread on the gas pedal mods.



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