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interesting IRS

 
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bcal
700RPM



Joined: 04 Feb 2021
Posts: 711
Location: The Shire, Sydney

Posted: Sun May 30, 2021 12:19 pm    Post subject: interesting IRS

Has anyone considered using one of these.

It's from a MX-5
Looks to me like it would bolt up nicely under a chassis with a large kickup.
Not sure of the width.
May not be suitable for high powered applications but would be ok for a small V8, 6 or 4.
Also you would have to consider changing it to 5 stud.
Anyhow, may be worth a looksee.
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Jimmy B
Cruisin



Joined: 01 Feb 2021
Posts: 339
Location: Tweed Valley, NSW, Australia

Posted: Sun May 30, 2021 2:33 pm    Post subject:

Ah, a subject I have some experience with!

The RX-7 (series 4or 5? ) Hubs and brakes fits the MX-5 uprights and the RX-7 diff also bolts straight into the MX-5 cradle, the RX-7 half shafts have to be shortened (from memory). Bullet Supercars ended up using the Crapadore Hydra-trac diffs (they had to build a special mount to bolt it to the standard MX-5 mountings) because they have a larger numbers of diff ratios and are more common! This is what they were doing in '98/'99 when I did work experience with them. So I'm unsure how or what Bullet are using these days!

Hope this helps if anyone thinking of the MX-5 setup!!

p.s. I'll try and post a couple of pics if I can find them
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bcal
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Joined: 04 Feb 2021
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Location: The Shire, Sydney

Posted: Sun May 30, 2021 3:28 pm    Post subject:

Thanks Jimmy.
With the Crummydore diff and RX7 brakes it may be a viable alternative to the good 'ol Jag.
I've been toying with the idea of using the uprights and control arms in the rexarod.
Another alternative was using WRX uprights with fabricated lower Z arms and top A arms. Only problem with the WRX is that they are macstrut but it wouldn't be too hard to fab a pivot mount where the strut bolts to the upright.
The MX-5 has the benifit of having upper and lower control arms ready to go plus coilovers. This should make things easier come rego time too.
Problem for me tho was the 4 stud hubs so thanx for the RX7 tip.
They are 5 stud I presume
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Jimmy B
Cruisin



Joined: 01 Feb 2021
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Location: Tweed Valley, NSW, Australia

Posted: Sun May 30, 2021 7:27 pm    Post subject:

The RX-7 diff will handle a Lexus DOHC V8. But has a 4.11 ratio, other ratios are harder to come by.

I'd suggest to anyone thinking about using this setup to use the RX-7 diff as the mount is cast as one piece with the diff housing & bolt straight to the MX-5 mounting points.
It would be best to buy a complete MX-5 & RX-7 rear from a jap importer as you would have all the parts needed and you could sell the leftovers.

Using the Crappadore diff you need to fabricate a custom mount and adapters to adapt the CV joints to the Crappadore diff.

I remember the basics as I want to use this kind of setup under a project in the future.
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Jimmy B
Cruisin



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Posted: Sun May 30, 2021 7:33 pm    Post subject:

almost forgot RX-7 are Ford bolt pattern.
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boxhead
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Joined: 12 Apr 2021
Posts: 11
Location: Alice Springs

Posted: Sun May 30, 2021 10:35 pm    Post subject:

Here is a link to a site showing the irs that I have in my Cobra replica, it is AU falcon XR6. http://www.clubcobra.com/photopost/showphoto.php?photo=13298&password;=&sort;=1&cat;=500&page;=1

The falcon irs comes in a cradle that would be fairly easy to fit into a chassis, my kit doesnt use the cradle it has all the mounting points welded onto the chassis. The only thing could be that the falcon irs is very wide.

Here is a link to a fellow Cobra builder useing the same kit as me and you can see how wide the setup is (this car has spacers and proper knock off hubs) My wheels will have different dish shape to the rims due to me not useing real knock offs. http://www.clubcobra.com/photopost/showphoto.php?photo=14209&password;=&sort;=1&cat;=all&page;=1

The bmw rear end is used in a Cobra kit called superformance, Another Cobra friend has one and it is powered by a supercharged gen III with 6 speed, he hasnt mentioned any diff issues and he isnt afraid to use the loud pedal.
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bcal
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Joined: 04 Feb 2021
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Location: The Shire, Sydney

Posted: Mon May 31, 2021 3:57 pm    Post subject:

Thanx BH.

I remember thing Hmmm when I first saw a cut away of the AU setup several years ago at the Sydney motor show.
Maybe a set of those hubs and control arms would be an option for my car.
Any idea of what they go for?
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boxhead
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Joined: 12 Apr 2021
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Posted: Tue Jun 01, 2021 11:47 pm    Post subject:

I bought my rear end complete from a wrecked XR6 from the Melbourne tradeing post for $1000.00 about 12 months ago.
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Jimmy B
Cruisin



Joined: 01 Feb 2021
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Location: Tweed Valley, NSW, Australia

Posted: Wed Jun 02, 2021 11:32 am    Post subject:

Here is the pic of the RX-7 rear in the MX-5 cradle as used by Bullet Supercars.

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bcal
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Joined: 04 Feb 2021
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Location: The Shire, Sydney

Posted: Wed Jun 02, 2021 4:08 pm    Post subject:

Quote:
I bought my rear end complete from a wrecked XR6 from the Melbourne tradeing post for $1000.00 about 12 months ago

Wow that's too dear for a fish arse like me. But I spose if you can use the springs etc it's probably cheaper than a decent pair of coil overs on their own.

Jimmy that Mazda rear end looks like a neat fit. what's it in?

I'll probably end up using WRX rear uprights and fabing my own control arms. At least the rex is 5 stud and they have pretty good brakes Plus no probs matching the half shafts etc. Only problem is repacing the macstrut with a bolt on upper control arm pivot, but that's not too hard.
Here's a pic of one.

And this is the type of control arm set up I want to build

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bcal
700RPM



Joined: 04 Feb 2021
Posts: 711
Location: The Shire, Sydney

Posted: Wed Jun 02, 2021 4:15 pm    Post subject:

Here's another interesting irs that I've dug up
Porsche 928 Wiess type suspension.


Would look nice with all the alloy bits polished up, but pricey
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Jimmy B
Cruisin



Joined: 01 Feb 2021
Posts: 339
Location: Tweed Valley, NSW, Australia

Posted: Wed Jun 02, 2021 4:44 pm    Post subject:

In this

RX-7 front suspension RHS chassis etc etc.

This is the first Bullet with Lexus V8, I fabricated those alloy brackets on the side and polished most of the alloy bits and fabricated a few other bits.

Those two MX-5s in the rear with no fronts are how they come from Japan.
Blue car behind green car is the 1st & 2nd car built & is powered by 13B rotary.
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