Five lug on a Miata rear?

It was a pub idea. The kind of idea that usually doesn't progress past the 2 ibuprofen the morning after.

Someone said "Man, It would be cool to do IRS on that car". All agreed and much tapping on phone screens later it was decided the Miata rear end was the correct width. We discussed how RX7 and Ford IRS pumpkins have been wedged into the subframe in the past so LSD's and gearing options were unlimited. "I hear they are easy to swap to five lug too!" said another. Glasses were raised and we all congratulated each other on just how clever we all were.

Fast forward a few weeks and I now own a NA miata rear end.

Preliminary measurements look promising but before I go too far I spent 20 minutes googling 5 lug swaps and have come away thinking the internet is a terrible, mean spirited place. Every discussion has pages and pages of heated debate on the necessity of the swap, questioning the parentage and sexual inclinations of those who dare suggest its possibility and zero actual info on how. I can see the RX7 pieces will not work just by looking at the bearing specs.

So anyway. I would like to fit 5X114.3/5X4.5" wheels on miata uprights. How should I go about it? Custom machining is an option.

If it is already close to 4x4.5 BP, I would just re drill the hubs and rotors.

Depending on offset limitations, a bolt-on wheel spacer/adapter might be your best option. That'll keep you from having to mess with the brakes, too. Give these guys a call or check out these ones on eBay.

I know V8Roadsters was looking at having custom rear hubs made that would use stock Miata halfshafts. Those could easily be drilled for a different pattern. This is probably the smartest option.

If you have machining chops, then I'd start by overlaying the two patterns to see how they look. It might be possible to just modify the stock hubs, but IIRC they're not flat on the back.

In reply to Keith Tanner:

And here I was hoping you would have the definitive "here's how to do it" answer.

http://www.geocities.ws/crash41301/diff.html

Looks like some folks are turning the RX7 hubs down to match miata dimensions. I will have to find one to check out.

It's never been a priority for me, so I've never bothered to look into it too closely.

In reply to Jumper K. Balls:

"So anyway. I would like to fit 5X114.3/5X4.5" wheels on miata uprights. How should I go about it? Custom machining is an option."

Actually pretty straightforward. The Tbird/Cougar/Lincoln hubs are very similar to the Miata hubs, about .080" larger diameter. And the splines are different. Unfortunately, they're also 5X4.25. 5X4.5 can be had in the form of "Cobra" hubs, but they're a little pricey. So this was my solution:

http://miatav8.blogspot.com/2014/02/five-lug-conversion.html

In reply to cvx_20:

Thank you good sir.

The 5 lug 3rd gen protege (Mazdaspeed Protege, Protege 5, ES) has a 5x114.3 bolt pattern and shares the same wheel bearing (Same mazda part number) and spline count (protege front, Miata rear) as the NA miata. Joefis racing is using them on his miata. He said they clearanced the caliper and installed a cut down Protégé rotor to fit under the caliper bracket.

So getting the 5x114.3 bolt pattern installed is not a problem as long as you can figure out brakes.

http://forum.miata.net/vb/showpost.php?p=6742001&postcount=15

moxnix wrote: The 5 lug 3rd gen protege (Mazdaspeed Protege, Protege 5, ES) has a 5x114.3 bolt pattern and shares the same wheel bearing (Same mazda part number) and spline count (protege front, Miata rear) as the NA miata. Joefis racing is using them on his miata. He said they clearanced the caliper and installed a cut down Protégé rotor to fit under the caliper bracket. So getting the 5x114.3 bolt pattern installed is not a problem as long as you can figure out brakes. http://forum.miata.net/vb/showpost.php?p=6742001&postcount=15

Your link only gets me the single post. I could log in but I gave up on M.net back around Miata #5 (on #14 currently). I'm interested to see what "clearencing" was done and what the rotor size difference was. Judging by the signature he has an early NA, while there should be (Keith can correct this) four different rear brake caliper mounts and rotor size: NA 1.6, NA 1.8, NB, NB sport.

Anyway, this has me intrigued as I'm about to buy wheels for my 2001 LS.

In reply to cvx_20:

Does the ford hub have the same splines as the Miata axle?

cvx_20 wrote: In reply to Jumper K. Balls: "So anyway. I would like to fit 5X114.3/5X4.5" wheels on miata uprights. How should I go about it? Custom machining is an option." Actually pretty straightforward. The Tbird/Cougar/Lincoln hubs are very similar to the Miata hubs, about .080" larger diameter. And the splines are different. Unfortunately, they're also 5X4.25. 5X4.5 can be had in the form of "Cobra" hubs, but they're a little pricey. So this was my solution: http://miatav8.blogspot.com/2014/02/five-lug-conversion.html

Result!

Junkyard_Dog wrote:

moxnix wrote: The 5 lug 3rd gen protege (Mazdaspeed Protege, Protege 5, ES) has a 5x114.3 bolt pattern and shares the same wheel bearing (Same mazda part number) and spline count (protege front, Miata rear) as the NA miata. Joefis racing is using them on his miata. He said they clearanced the caliper and installed a cut down Protégé rotor to fit under the caliper bracket. So getting the 5x114.3 bolt pattern installed is not a problem as long as you can figure out brakes. http://forum.miata.net/vb/showpost.php?p=6742001&postcount=15

Your link only gets me the single post. I could log in but I gave up on M.net back around Miata #5 (on #14 currently). I'm interested to see what "clearencing" was done and what the rotor size difference was. Judging by the signature he has an early NA, while there should be (Keith can correct this) four different rear brake caliper mounts and rotor size: NA 1.6, NA 1.8, NB, NB sport. Anyway, this has me intrigued as I'm about to buy wheels for my 2001 LS.

There are no in process pictures that I have seen just a few pics of the whole car with the 5x114.3 wheels on it. I have seen the car with the 5x114.3 wheels on the rear in person (this is a rear only solution I don't know about the front).

A bit more detail in this post. http://forum.miata.net/vb/showpost.php?p=6743639&postcount=27

Junkyard_Dog wrote: Judging by the signature he has an early NA, while there should be (Keith can correct this) four different rear brake caliper mounts and rotor size: NA 1.6, NA 1.8, NB, NB sport.

Three. NA 1.8 = NB.

bgkast wrote: In reply to cvx_20: Does the ford hub have the same splines as the Miata axle?

No. But that wasn't the question :) I read it several times just to be sure.

The scheme I used works best with heavier axles and rear end as found in a typical V8 swap.

In reply to cvx_20:

What did you use to cut down the front spindles? Lathe? If so, what size lathe?

My usual machining sources don't have lathes large enough, so they say.