Shortening half-shafts (IRS conversion)

[Nathan Acree]

Hello,

I have a question for all of you racers out there who might be more familiar with some of the better fabrication shops around the country.

I am looking for options for installing an IRS in my GT, and for now the Miata setup looks like the best bet, but it would certainly have to be narrowed to fit a stock GT.

What I am looking for is a place that has the expertise to either properly shorten the Miata half-shafts or fabricate custom length ones.

Anyone have any ideas as to who I might be able to send these things to to get this done?


Nathan Acree
Albuquerque New Mexico

[David McCollam]

Nathan,

No good driveshaft shops in your area? That's what I'd try first. They should be able to take the Miata shafts and shorten them or use the CV joints from the ends and make new shafts.

Good luck.

[Travis]

Nathan,

I don't know how the axle width of the miata compares to the GT, but maybe you could use a wheel with a larger backspace instead? As soon as you start shortening the control arms, the suspension geometry will be changed. Different camber curves, instant center locations and so on....

Just a thought

If not, you might try driveshaftshop.com though some racers have found their shafts to be somewhat over rated. Right Bob?

-Travis

[baz]

remember you have to narrow the whole thing so its not just a drive shop job

as travis says there are loads of changes going on
the only IRS i knoew thats a straght cut and weld is the jag
i have an artical some where and will scan it soon to show you
it even has a cut lenth in it to get the desired width

[Nathan Acree]

Guys,

Thanks for the info. The idea was to use the diff and its mounts and fabricate a suspension cradle and new upper and lower control arms coil spring mounts etc.

I would love to be able to use the miata supension subframe and have all of the mazda designed geometry intact, but there is just no way it would fit even a GT with fender flares and different offset wheels, the subframe itself is just too wide.

I'm just trying to get some ideas for IRS, and the Miata stuff is cheap and plentiful.

I'm open to any other suggestions.

Nathan Acree
Albuquerque New Mexico

[jtb]

Hi,

I, too, longed for a Miata IRS in my GT, but I just couldn't find one. Hearing you say it won't fit makes me feel better (Sorry, I don't mean to benefit from your misery :o )

I am in the midst of altering an IRS unit from a BMW 325 to fit the Opel. I'll let you know how it goes if you're interested. I'm still going to have to run a high offset wheel, (something from a FWD) but that doesn't bother me, as I won't have to narrow the axles.

Attached is a picture - step one is drilling these large ugly holes in the moustache bar to move the attachment points inward to line up with the GT's box section (~ 36" Ctr to Ctr). Later the stock mounts will be chopped off.

James