I have decided its only worth swapping any sub-frame (with Steering Rack included) to a NA only if its broken, its just too many hrs of intense labor, welding and 22 bushings.

 

More details.

Front: the lower control arm mounting points are moved for a bit more caster. The NB steering rack has a stronger mounting. I'm not 100% sure on brace modification points. I would recommend going to the NB spindles, which also means you want the NB upper control arm due to a change in the ball joint. NB arms also have more reinforcements as well as that modified sway bar end link mounting point.

Rear: The subframe geometry is identical. The mounting points for the braces changed, but are the same for all NBs - you can attach the stronger 01+ Sport braces to the 1999-00 subframe, although you'll find you're missing one of the twin bolt holes on the tub. Exhaust hangers were moved. The uprights have 5mm more track on each side. Again, the control arms are dimensionally the same but have some extra reinforcements.

No welding is involved to swap them around - my 1994 Targa car has a set of 2005 subframes on it. It also has an NB exhaust so the exhaust hanger changes aren't a problem.

 

I think the best bang for the buck is the front subframe due to the better pickup points.

 

He (OP) has both of them.

 

That is wrong the rear suspension geometries are Identical. the difference in 5mm track width differance is because the stock wheels went from 45mm offset on the NA to 40mm offset on the NB.

If you followed the armchair engeneers on Miata.net from the mid to late 90’s this should have caused the rear wheel bearing to explode by running anything other than the stock 45mm wheel offset.

Bob

 

Bob. the track increase came from the wheels and a change in geometry in the rear. Check the specs and you'll see the NB rear track increased more than the front. You can also check the factory 1999 Service Highlights book - that's where the 5mm number comes from.

However, the statement that it's from the subframe is incorrect. It's the hub carrier that changed.

 

So the extra 5mm in the rear came from the Hub carrier? What is the hub carrier? Spindle, lower or upper arms? I just put 01+ rear hubs/spindles with 95 axles and it appears the axle doesnt seat completed in hub, a few mm off?

NVM-it is what the hub is pressed into. Do you think it's safe to run the 95 axles with 01+ hubs being that the surface of the large part of the axles don't seat fully against the hub carrier?

 

Track widths f/r

NA 55.5/56.2
NB 55.7/56.7

So 5mm difference per side is in the wheels. That would mean the NB suspension geometry is ~2.5mm narrower per side in the front and ~1.35mm per side wider in the rear.

So the NB rear upright puts the wheel 1.35mm further out I guess. That is like negligible in my opinon. I almost wonder if it is round off error and a units conversion by the marketing folks.

The change in front geometry and rack mounting is a bit more significant however.

Bob

 

From the 1999 Service Highlights book.

 

So that make it a total of 10mm difference in width in the rear? I wonder how this is going to make my car drive...

 

Ok so in reality the rear track on an NB is 20mm wider than an NA, 10mm for wheels and another 10mm for the knuckles, and the marketing people in the brochure call it 1/2"

Bob

 

It will handle the same as it would if you were to add 5mm spacers to your old setup. The rear geometry of the NB with stock wheels is the same as a NA with 10mm wheel spacers on its stock wheels. and the 5mm you get from the uprights won't make much difference that it would be very noticable.

It wouldn’t surprise me it the real reason mazda widened it wasn’t to go after improved handling. I would about bet it was because the Clay model guys in styling got into adding more clay and then when they were real happy with the shape of the fender they found the wheel looked too far inboard compared to the fender so the styling guys petetioned to have the wheels pushed it out not the handleing guys.

I will also say running less offset on the wheels doesn’t screw up the handling of the car at all in the case of the Miata. I think my car handles and feels better than it ever did now with now 20mm spacers behind 15X9 949 wheels. I don’t think I’ve gotten to the point of diminishing returns yet, wider is better.

Bob

 

for a street / autox car this seems counter intuitive. Wouldn't you want less caster for quicker steering?

 

Well, the NB cars are quicker in autocross aren't they? So I guess it worked

 

Any idea as to whether the MSM uprights are the same as the other NBs?

 

I believe the hubs are different but the uprights are the same. Remember, the MSM has fatter axles so there need to be changes to accommodate that. No geometry changes of which I am aware.

 

I am digging the idea of picking up a nb front subrfame. Thanks for all the info guys!

 

So the NB axles are 5mm longer then the NA axles I am getting mixed reviews and I see lots of part stores list the same p/n. Im talking a late NA not the early 1.6.

 

Wow, are we still having this conversation?

The axles are the same size for all 1.8 cars except the MSM. The early 1.8 NAs (94-95ish) originally used two-piece axles, but they are all dimensionally compatible.

The part numbers varied during the original production run as the design of the CV joints was tweaked several times, but as service parts, Mazda lists the same unit (MD-25-500) for all non-turbo, ABS-equipped 1.8 cars in the Collision Guide:

 

Awesome thanks the info I was looking for.