J.A. Ackley
J.A. Ackley Senior Editor
10/4/23 8:30 a.m.

Why an NA Miata? Well, for more than 30 years, it’s remained a viable answer to nearly every question. Autocross. Hillclimbs. Time trials. Rallycross. Road racing. Modern-day or vintage classes. It works for all of the above.

Sure, the newer Miatas feature many improvements over the original. However, there’s just something about the NA Miata.

Maybe it’s the pop-up headlights, …

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AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) GRM+ Memberand PowerDork
10/4/23 5:00 p.m.

You definitely interviewed the right person for this article.  I look forward to reading it all later.

Colin Wood
Colin Wood Associate Editor
10/5/23 10:04 a.m.

In reply to AnthonyGS (Forum Supporter) :

It's also really cool that Keith is a regular here on the forum. He always has some really good advice to offer.

AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) GRM+ Memberand PowerDork
10/5/23 2:10 p.m.

In reply to Colin Wood :

It was a good read.  Of all the cars I have ever owned, my 94 Miata R is one of the ones I wish I still had.  

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
10/5/23 5:53 p.m.

Being a suspension geometry nerd, I am curious about what the specific differences are between NA and NB.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/5/23 6:58 p.m.

In reply to Pete. (l33t FS) :

Every year, Mazda publishes the "service highlights" that goes over the changes for the new year. The 1999 one is a gold mine.

Upper mounts: single piece to replace the old multi-piece one. Urethane bumpstops for better cornering. 
Front subframe: lower control arms moved forward by 2.1mm and upper arm moved backwards 3mm for more caster trail. Lower arm also moved down by 5.7mm for lower roll center. Steering gear mount is more rigid. 
Rear subframe is the same geometry as before but has more bracing.
Front knuckle: Steering arm moved up by 7.1mm for bump steer control. Different taper on the upper ball joint but that's not mentioned.
Rear shocks have 10mm more stroke. Rear knuckle moves the mounting flange out by 5mm each side to widen the track.

The NB Yamaguchi book goes into the reasons for a lot of these decisions.

AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) GRM+ Memberand PowerDork
10/6/23 10:29 a.m.

The Yamaguchi book is really good.  Did he write the FD RX-7 one too?  It's also amazing.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/6/23 1:09 p.m.

For anyone who wants to retrofit NB geometry up front, you need to swap the rack/subframe/upper control arms/knuckles at a minimum.  Lower control arms are the same geometry. The widened track in the rear can mean tire interference on the narrower NA body - my Targa Miata is built this way, with the complete NB front end and the NA rear uprights attached to an NB rear subframe due to improved bracing options.

fidelity101
fidelity101 UberDork
10/6/23 1:44 p.m.

In reply to AnthonyGS (Forum Supporter) :

I have his FC book and the miata book - they are great

grubinski
grubinski New Reader
10/8/23 9:54 a.m.

Keith ... do you know if the V8R front subframes use NA or NB geometry?  Reading between the lines "my Targa car has "the complete NB front end" makes me think that V8R used NB geometry, since your Targa car has the V8 swap.

Given that the front knuckle changed on the NB, should I be running an NB knuckle with the V8R subframe for optimum bump steer?

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/8/23 10:44 a.m.

Yes, my V8R subframe has NB geometry. I don't recall if they all do or not, but it's certainly a question for them. I would recommend beefing up the steering rack mounting tabs with gussets as well. 

grubinski
grubinski New Reader
10/8/23 10:49 a.m.
Keith Tanner said:

Yes, my V8R subframe has NB geometry. I don't recall if they all do or not, but it's certainly a question for them. I would recommend beefing up the steering rack mounting tabs with gussets as well. 

Thanks!  I'll ask them.  Seems like I should run an NB knuckle if the rest of the geometry is NB.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
10/8/23 1:16 p.m.

You'll want the NB upper control arm as well. 

I do seem to recall that they all have the NB geometry, but you'll want to confirm that. 

LLL
LLL New Reader
2/14/24 3:04 p.m.

I have a question about changing an automatic car to a manual transmission. With automatic cars often selling for far less it seems this might be worth the effort.  I did read an article that said don't do it because you will never sort out warning lights or something electrically related. Is that true?

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
2/14/24 6:08 p.m.

In reply to LLL :

On a 1.6, it's relatively easy because the transmission is basically standalone. The 1.8 is more challenging as the transmission is controlled by the ECU. I probably wouldn't bother in the latter case unless there's a very compelling reason to use a specific car.

There's a good article on the 1.6 manual swap on the Miata.net garage. 

LLL
LLL New Reader
2/22/24 12:32 a.m.

Thank you

Rodan
Rodan UltraDork
2/22/24 8:19 a.m.

In reply to grubinski :

As a data point, the V8R subframe sold by KPower is also NB.  

Additionally, V8R has updated the rack brackets on the newer subframes, so it appears they are at least trying to address the cracking issues.  The new brackets are angled out rather than 90* where they attach to the crossmember and they are boxed in.  Still probably a good idea to keep an eye on them, especially if you're tracking the car on wide, sticky rubber.

 

Rodan
Rodan UltraDork
2/22/24 8:25 a.m.

In reply to LLL :

I know the thread is about NAs, but it is possible to convert an NB.  In the '99-00 at least, the transmission is controlled by a separate control module.  I removed the TCM and used a manual trans  ECU in mine.  I occasionally get a code for the neutral safety, which the ECU can't find because the wiring is not there.  No other codes related to the transmission swap.  

 

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