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A long time ago I saw a build thread where someone extended the rear control arms to make the car accept Thunderbird axles.
I am entertaining this idea. I would like to find that old build thread.
sometimes Google does a better job of indexing pages than the forum itself. So don't hesitate to try something like: site:v8miata.net v8 swap thunderbird axle
I see some threads on miata.net on this. I recall what you're talking about, but never explored the idea.
There is an alternative. Ford produced a Mustang with an independent suspension between 1999 and 2004 called the Cobra R. The 1999 version used 28 spline inner shafts and 28 spline outer shafts while all of the rest use 28 spline outer shafts and 31 spline inner shafts. The center section of the Ford 8.8 comes in two variants, one accepts 28 spline halfshafts and the other accepts 31 spline halfshafts which are larger. Both axle types are larger than the Thunderbird axles. The 28 spline outer ends fit the Cobra R 5 lug hubs which are much stronger than the Miata Hubs. A set of axles are available from summit racing or e-bay for $180.00 and hubs will cost another $250.00 or so. You will still have to make new control arms as these new shafts are 31 inches long compressed and the miata ones are about 29 inches compressed. I am building new Chromoly control arms for mine along with a new rear crossmember for the 8.8.
There is an alternative. Ford produced a Mustang with an independent suspension between 1999 and 2004 called the Cobra R. The 1999 version used 28 spline inner shafts and 28 spline outer shafts while all of the rest use 28 spline outer shafts and 31 spline inner shafts. The center section of the Ford 8.8 comes in two variants, one accepts 28 spline halfshafts and the other accepts 31 spline halfshafts which are larger. Both axle types are larger than the Thunderbird axles. The 28 spline outer ends fit the Cobra R 5 lug hubs which are much stronger than the Miata Hubs. A set of axles are available from summit racing or e-bay for $180.00 and hubs will cost another $250.00 or so. You will still have to make new control arms as these new shafts are 31 inches long compressed and the miata ones are about 29 inches compressed. I am building new Chromoly control arms for mine along with a new rear crossmember for the 8.8.
about how much do you think the whole IRS,,,hub to hub will weight ?
If you are really interested in doing the rear suspension for a V8 powered Miata you should take a close look at the build thread Vorshlag Motorsports in Texas started for their Miata project. Their approach is similar to mine, no kit, just a whole lot of fabrication for crossmembers and chromoly a-arms. They didn't get into the mathematics behind their design and if you can't calculate roll centers, camber change, and scrub I don't recommend you try copying what they did. BUT what they did is a whole hell of a lot safer than trying to extend some folded up sheet metal A-Arms by welding in pieces of metal. That approach is a great way to die in a crash when something breaks.
05-20-2020, 07:18 PM
Extended rear control arms and Thunderbird axles
