GameboyRMH SuperDork
Nov. 19, 2010 9:30 a.m.

Hey I was just reading the GRM article on Targa Newfoundland and saw that Keith's Miata basically has the 2005 "doughboy" Miata suspension and steering swapped in. Do these have better geometry than the NA Miata and how straightforward is the swap? I see it has the strut braces swapped in as well.

Just curious.

mistanfo
mistanfo SuperDork
Nov. 19, 2010 10:12 a.m.

Front NB subframe has better geometry. You need more than the subframe, though someone else will have to come in with what parts those are. Steering rack and some of the a-arms, though I can't be more specific. IIRC, the rears have more travel, though that can be taken care of (largely) with FM rear mounts.

Keith SuperDork
Nov. 19, 2010 10:36 a.m.

"Doughboy"? What?

The front NB subframe does have some improved geometry. The lower A-arms are moved forward. The steering rack has better mounts. The front uprights have the steering arm moved up about 7mm, and the upper control arms have a slightly different taper on the ball joint and more reinforcements. If you're going to swap the front, you ideally need to do the subframe, rack, uprights, upper control arms and maybe the tie rods - not sure about the latter. If you have those parts, it's a straight bolt-in.

The rear subframe is identical other than exhaust hangers and brace mounting points. It did let me run the stronger rear subframe brace which was good, because I planned to use the brace as a skid plate. And I did, big time. The rear uprights give an extra 5mm of track on each side, so I used 1994-97 uprights to give myself a bit more fender clearance. Again, this all bolts together although the 1.6 cars don't have the mounts on the chassis for the subframe brace and you'll find the exhaust hangers are in the wrong place for an NA exhaust.

The extra travel comes completely from the spring/shock/mount assembly. Put in a full set of NB springs/shocks/upper mounts (FM's suspension packages come this way if you want) and you'll have the NB travel. I went further with my AFCO setup, but the subframe wasn't a contributor.

As an added bonus, I got some front uprights from a car with ABS, and my rally computer uses that for a trigger. Means wheelspin doesn't affect my mileage readouts.

The shock tower brace in the engine bay (usually called a strut brace) wasn't used, but I did use the front and rear subframe braces. Those 2001+ rear subframe braces are strong.

amg_rx7 HalfDork
Nov. 19, 2010 10:36 a.m.

Doughboy???

Slyp_Dawg Reader
Nov. 19, 2010 11:04 a.m.

is there an appreciable handling difference between a NB-suspended NA and a regular NA, and is that handling difference appreciable enough to justify pretty much tearing the car apart from the firewall forward and sourcing all the NB components to be swapped over, for a autoX/street car?

GameboyRMH SuperDork
Nov. 19, 2010 11:19 a.m.

Oh so it's from an NB, I thought it was from an NC (AKA "doughboy") Miata.

Marty! Dork
Nov. 19, 2010 3:33 p.m.

Like this?

Keith SuperDork
Nov. 19, 2010 5:32 p.m.

It's not "tearing the car apart from the firewall", there are about 6 bolts holding the front subframe on. Support the engine, unbolt the brake calipers and steering column, and drop it out the bottom. Pretty quick job really.

The handling difference isn't huge, but it's there. The springs/shocks/mounts probably make the biggest difference, making the car more compliant. The geometry changes are more subtle.

Keith SuperDork
Nov. 19, 2010 5:34 p.m.

Marty, thank you for that. It's stuck in my head now.

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