Small Rear ends or Miata rear subframe

So for the Midget, is there anyway to get a Miata rear subframe into it or will that take a massive amount of fabrication? What are some small live axles (other then 1st gen RX-7 which I have had trouble finding)?

As one who has both a Mk II Sprite and an NA Miata, and who has had all that stuff laid out on the ground a time or three -

Not such an easy one:

• Miata rear track width 56.2"

• Sprite-Midget rear track width 44.75"

There really isn't enough meat to section a foot out of the whole package, and the Midget/Sprite rear suspension bay isn't terribly roomy.

There are any number of multi-link coil-over setups I've seen on Midget/Sprite race cars. Huffaker racing or engineering I believe sells a weld-in kit.

The RX7 seems the way to go - look around in some of the Locost forums; people building the "original book" chassis are always looking for short live axles.

What about a Pinto rear end?

That sounds like a GREAT excuse for some epic fender flares. (Miata F/R subframes) Modify for an inboard suspension a la Zamboni From Hell and you'd have a sick GRM-style GT500-looking car.

Well I was going to build some massive fender flares. The original plan was a 1st gen RX-7 rear end and wide flares. The reason I am looking for a new rear end is that I want to throw more horsepower then the stock rear end can handle.

Ignoring the track width, there's going to be a fair bit of fabrication. You'll have to build a cradle for the rear subframe, whereas the car is already built for a live axle. I considered the same for my MGB and ended up sticking with the live rear. Of course, I had an interior to take into consideration, which you don't.

This is what happens when you try to put a normal car width rear axle under a midget. The wheels stick out.. A bunch.

I recommend narrowed RX-7 live axle with a fairly straightforward 4-link with converging upper links. You can fab some brackets that use the stock shock mounts for the upper links, and the lower links can use the front spring eyes. there will be some fab work involved and som $$$ but not to much of either.

http://the-mite.com/

Also, the RX2 / RX3 rear axle is much shorter than the RX7, and parts swap around. The GLC uses the same width rear as an RX2 also, 52" flange to flange.

My friend has a machine shop but I didn't want to charge machine shop time into the budget. The guys that I am going to be working with on this project have plenty experience with composites which is why I was going to go with a normal size axles. What is the bolt pattern of the wheels on the RX-3 and is the pattern different for the GLC?

You might ant to look at early Toyota rears. Should be easy to source and relatively cheap. I also agree that it makes sense to stay with a live axle.

Are the Toyota rear ends or the Pinto rear end wider or heavier or is there some other reason that the RX rear ends seem to be the only ones suggested?

All those cars used the 4x110 bolt circle. I narrowed an RX7 axle, it's not as hard as it looks. I used the basic information from the-mite but I discovered something: the Mazda bearing carriers have a locating 'snout' machined on them which is a tap fit in the axle housing, if you don't cut the housing off too short, meaning you need to cut it outside of the housing 'taper'. The RX2 taper doesn't go as far out on the housing as the RX7, meaning it would be easier to shorten. You have to make up the two outer aluminum locator blocks like he used, but that's simple for anyone with a lathe. In fact, I think I still have mine laying around somewhere. I bored the center a bit oversize and then wrapped brass shim stock around a piece of steel tubing to get them tight, then aligned everything and tapped the housings in and welded them in place. You'd just need a long enough piece of steel tubing and remember to weld four places 90 degrees apart first, check the alignment by turning the tube, if it's good then burn 'em together. I didn't use the center blocks since the bearing retainers were a tight fit in the housing, but I did use a micrometer to check the distance from the tubing to the differential bearing mounting area both before and after the housing was cut, it was within .002".

Once that's done the axles need to be shortened and resplined, Moser does that. Dutchman Motorsports will do it too but their shop foreman has something of an attitude problem. And you can quote me on that.

Most any machine shop can redrill the flanges for any bolt circle you want.

I think the reason the RX axles get used more is there's a readily available limited slip, Miata gears bolt right in, etc.

EDIT" I've also narrowed a Miata rear subframe to get a 50" rear track (it was going under a Opel GT), that's pretty much the limit and even then some suspension geometry changes happen. You have to have the Miata CV axles shortened and resplined. Take my advice: don't try to cut them and reweld them, it doesn't turn out too good.

i dont know just how narrow it is, but a guy i knew on another forum was using a hyundai pony rear axle for a locost i believe.

actually he's on here as ArthurDent if you wanted to contact him

How much would getting the axles shortened and resplined cost me?

The Miata axles cost $150 a pair to shorten and respline.

In reply to Jensenman:

How much time did it take on the lathe to shorten the rear end?

Didn't use a lathe to cut the housing. I used a really big tubing cutter to make a ring around the housing as a guide, then cut it with a recip saw. I cut it slightly outboard of the ring, then used a side grinder to get it to the ring. There's no point in trying to get that cut 100% perfect, it's the bearing carrier alignment that's important and that's the purpose of the locator blocks and the tubing.