9 Inch diff conversion - info needed

nfs13b · Postby **nfs13b** » Thu Sep 13, 2007 3:14 pm

ok people, now I know all the crap from previous posts that mx5s are corner cars and not straight line cars yada yada yada, but 9.8 seconds means the car is coming along pretty good.

I am looking to step things up next year, looking to put some slicks on the car and head for the 8 second zone. I cant do this with my IRS setup in an mx5.

So, I am looking for information from people that have put a live rear end in an mx5. I dont think there would be many people on here that have actually done it but surely there are pople that have read about others doing it. I have searched the miata.net site but cannot find too much info....

Also This will mean that I will be selling off my extremely tuff IRS setup. It will be probably be a complete bolt in setup with the borg warner diff, 28 spline billet axles, CVs, commodore hubs etc. This would be perfect for anyone building a big hp mx5. PM if your interested in this.

Thank you all

zoomzoom · Postby **zoomzoom** » Thu Sep 13, 2007 3:51 pm

Just a thought, maybe a de dion tube setup would be worth a look. It basically works all the same as the live axle but without so much unsprung weight, and the torque reaction to the tailshaft trying to spin the diff isn't trying to roll the car over sideways.

Benny · Postby **Benny** » Thu Sep 13, 2007 6:20 pm

I can't say where I saw it, but there is someone out there who makes Ford 9\" diffs for IRS set-ups.
Basically it is a 9\" diff in a custom housing for use in cars with IRS.

sprx3 · Postby **sprx3** » Thu Sep 13, 2007 7:03 pm

hey benny, he already has a borg warner irs set up in it (commodore conversion) ((if im not mistaken) he wants a normal diff....

Are you going to tub it as well?

i know there is one in the states thats tubed & has a 9\" but i cant remember if its been cut up or not, what size tyre do you want to run?

tbro · Postby **tbro** » Thu Sep 13, 2007 10:26 pm

nfs13b
My old boss had a series 1 rx7 with a 9' diff watts link rear end, it was the Qld sports sedan that he won the championship with, plenty of grunt, so I would talk to someone who prepared RX7's back in the 80s or 90s. Mike Dyer at Brookvale, he does a lot of race car engine machining, might be able to help with names etc. Hope this helps as the only people I dealt with were all in QLD.
Terry

ben wilson · Postby **ben wilson** » Thu Sep 13, 2007 10:44 pm

DJR used to do an independent 9\" setup for the Sierra touring cars, you might be able to get hold of one of them.

Failing that, have a look on the miata forum, I'm sure there is someone in the US who has done it. Perhaps a generic 1/2 chassis kit could be adapted?

nfs13b · Postby **nfs13b** » Fri Sep 14, 2007 9:11 am

Ok, some more information. The current IRS setup I have now is excellent, almost unbreakable and would be teriffic in a circuit car, but for straight line racing I think a good 4 link solid rear end is what I will need.

As for tubbing and cutting it up, im sure I will later but for now I want to compete in a class called street 289 and you cant modify the chassis rails. so I would be looking at making the arches bigger but thats about it.

I have already gone to methanol so the fuel tank in the back is pretty pointless and it seems once you remove that there is heaps of room.

The only info I have been able to find are some pictures here
http://home.cogeco.ca/~praxus5/

I run a 235/60 R15 tyre now (which is about 26in x 8.5in) and would be happy with keeping this size or perhaps stepping up to a 28in x 9in tyre. That would look pretty good on the mx5.