Questions about rear suspensions.

[diverrick]

I am newish to the forum and may not know what has already been covered, but a search did not show what I was looking for.

With all the Cobra kits out there, I here a lot about ford differentials or Jag IRS set ups.

I have not heard about how the ride is with any of the set ups, nor if they are using sway bars.

I know that my old mustang was converted to a Shelby front end, and with it a pretty big sway bar was added. It made a HUGE difference.

Do most of these Kits have sway bars built into the suspension?
And does a IRS set up give a better ride, when compared to a solid ford differential?

[bobcowan]

I have built and driven both solid axle and IRS. The IRS is so superior, I would never consider building another car like this with a solid axle.

Some people say the Jag rear performs better than the Ford. I don't know if that's really true or not. But the Ford is considerably cheaper, and much easier to buy parts for.

A sway bar will tie the two sides of the suspension together, in an attempt to balance one side against the other. The down side of that is if you tie them together, they're no long Independent.

For an IRS, the handeling should be managed primarily by by the springs and shocks. The sway bar (if there is one) is used for fine tuning of the car only. Like for a specific load or track.

I have a small sway bar on mine, but I only use it on the track. On the street I disconnect it. Same thing in the front.

[Jaydee]

I have a Ford IRS with a sway bar on the rear. I don't have one on the front as yet. Are you saying it may not be necessary?
JD

[xb-60]

Originally Posted by Jaydee

I have a Ford IRS with a sway bar on the rear. I don't have one on the front as yet. Are you saying it may not be necessary?
JD

Adding a sway bar to the rear of a car would tend to make the car more "tail happy". You would add a rear bar if the car was understeering too much. A Cobra could probably be described, in standard state with front and rear suspensions set up correctly (no sway bars), as tail happy to start with, so adding a bar on the back would probably accentuate this...
Cheers,
Glen

[vatdevil]

IRS...better ride and handling. Solid...better traction for straight ahead starts, higher power rating, and lower cost. Sway bar may or may not be necessary for IRS, depends on cars balance. It is best to have adjustable sway bars to allow fine tuning of balance.

[diverrick]

Cool, Thanks guys. I guess I will be adding IRS to my list.

[LMH]

Another thing to keep in mind is that IRS adds to its value. Someday, you're most likely going to sell it.
Larry

[CHANMADD]

Front and rear Jag suspensions..........shortened Granada front sway bar
and a rear sway bar from a Mazda 323 rear. I have no complaints about
the handling,

[mdross1]

When getting ready to my build wanted IRS but was hearing too many negatives about the Jag rear with lots of hp and big stickies out back so we went with narrowed 9". What is the source of the Ford IRS and it's hp capacity?

[bobcowan]

cars that have a Ford IRS generally use parts out of a Thunderbird or Mustang. Ford and other vendors often have the parts on hand.

But, unless you're a really good fabricater, you're pretty much stuck with whatever your car was designed to use.

As for power capacity, that's variable depending on use. For street use you'll have a tough time braking the pasrts. Drag racing, though, puts a lot of strain on parts. Things will break pretty regularly.

[joyridin']

You really need the IRS set-up from a 2003-2004 Mustang Cobra. They are a lot heavier duty due to the the terminator engines. They will hold up to 500 or more hp without too much of a problem. Earlier IRS versions did not have 31 spline etc.

[LMH]

Originally Posted by joyridin'

You really need the IRS set-up from a 2003-2004 Mustang Cobra. They are a lot heavier duty due to the the terminator engines. They will hold up to 500 or more hp without too much of a problem. Earlier IRS versions did not have 31 spline etc.

That's what I used along with a super strong rear cover with preload on the bearings. I also had The Driveshaft Shop make 300M axles for the center shafts. Turned out really nice.
Larry

[Jerry Clayton]

The IRS rears also benefit from the short,short drive shaft that is an big,big detriment on the solid rears------------

[lippy]

Originally Posted by Jerry Clayton

The IRS rears also benefit from the short,short drive shaft that is an big,big detriment on the solid rears------------

This is an important point. Since a Cobra has a very short wheelbase and a long engine, the length of the driveshaft is very short. So the travel you get for a solid rear with this geometry is so small that it really limits ride and performance. Based on geometry alone, the IRS should be far better in this application.

[john chesnut]

I know that it's sacrilege to use GM parts in a Cobra. But, I put C5 Corvette independent suspension in mine. The parts are aluminum. The geometry is great. And the rear is a double wishbone design. I would describe the handling of my tribute Cobra as extremely good.

The one thing about the C5 diff is that it bolts directly to the transmission. The Vette runs a transaxle. This will not fit in a Cobra. On my car I designed and had made a new input shaft with front plate that bolts to the Vette diff. This let me run a driveshaft. If I were to use C5 suspension now I would use the center diff from a new generation V8 Camaro.

The comments about running a rear sway bar only are correct. Generally if only 1 sway bar is run it is in the front. A rear only sway bar will tend to cause the car to be loose/oversteer.