Irs

willevans · #1 (**permalink**) 10-02-2001, 07:07 PM

I am building a cobra replica to be as light as possible. Carbon fiber body, aluminum small block, all space frame, etc. In order to keep everything razor sharp I was considering getting an Independant Rear Suspension to upgrade my car. Before I pay out the extra greenbacks I did some research and found that some people say that if your car is really light, you don't need IRS. What do you guys think? Can you notice the difference? I know the IRS cars are faster (though only be a tenth) on the track, but how much wieght does IRS add? Will it be noticable on a mountain road over an advanced solid axle setup?

loudpedal · #2 (**permalink**) 10-09-2001, 03:57 PM

In a road car you wont notice much of an improvement in handling ....assuming both the IRS and live axle are both set up correctly.

The IRS advantage shows up in less unsprung weight, and in the latitude of adjustability.

If I wer u, I would use the T-Bird super coupe irs unit as a base...not expensive and availiable. That is if your chassis conversant and can do fab work. Assembly/fab can be a problem, and can be expensive to send out. The live axle is pretty much of a "hang the springs and bolt it up deal. Hope I helped a little....

427sharpe · #3 (**permalink**) 10-15-2001, 10:09 PM

Another factor--a live axle tends to have MUCH less suspension travel in a Cobra--read harsher ride and limited grip on any rough surface. I think the TBird/MKVIII rear set up is very good, and the 8.8 can handle a decent amount of power. They are basically the same except the MkVIII (and SuperCoupe) have an aluminum center section, which sounds like your cup of tea. Very good adjustability, and easy to find/build/replace as req. A big advantage over the common Jag set up is outboard disc brakes as well.

aeroace · #4 (**permalink**) 10-15-2001, 10:33 PM

They handle as differently as night and day. Also, live axle cobras usually sit too high in the rear. I think IRS cars are easier to drive, the rear doesn't come around so easily, it's harder to induce oversteer. They offer more tuning adjustments, and have less unsprung weight.

Hank Dondero · #5 (**permalink**) 10-16-2001, 05:28 AM

Suggest you look at Cobra Forum and search IRS. There have been several posts on IRSs in FFRs. I have such a setup. As stock from FFR the suspension is adequate for the street. If you are going to go racing, be prepared to pay for suspension upgrades.

Hank
FFR 1776