Why a Rear Steer Kit for ’99 – ’04 Mustang Cobras?  Simple.  To help correct rear steering geometry issues in lowered Cobras. 
This all started in October of ’99 when I was fortunate enough to be invited to Road Atlanta by Ford Racing for the media preview and test drive of the Ford Racing FR500 Mustang prior to its unveiling at SEMA.

Ford Racing brought two ’99 Cobra based FR500 prototypes featuring a longer wheel base, SLA double wishbone front suspension, IRS rear suspension and the new FR500 5.0L 4-V engine.  All the Mustang media was there along with Rusty Wallace, Max Pappas and me.  The day was filled with test drives of the FR500 vs. a Corvette and a Viper.  The short answer is the FR500 was the much better driving and handling car of the three.  Except for one thing.

FR500 testing at Road Atlanta

With the double wishbone up front the FR500 had really good handling but I noticed something.  The added front grip brought out a small issue with the stock (geometry) rear Cobra IRS.  When I was really pushing it coming out of the slow right hander before the long straight, about half way through the corner the back wanted to get loose.  Again in the gentle right hander coming under the bridge at a pretty good clip, the back of the car felt unsettled – If anyone knows Road Atlanta, it’s not a place to loose confidence in the car’s grip.  Rusty never noticed it as he had the car sideways most of the time and Max did a phenomenal job of compensating his driving style for it.  Me on the other hand had less experienced drivers in mind, thinking that in a Cobra with my upgraded suspension and improved grip, the rear “looseness’” could be a problem for a lot of folks.

When I got back to the shop in Indy, I pulled up the Cobra IRS in my geometry program on my computer to try and understand just what was going on.  I discovered that in a lowered Cobra with IRS, once the body gets to a certain point of roll, both rear wheels instantly steer in the wrong direction.  That was one of those “Ah ha” moments.  That was the reason for the looseness I felt half way through the turns.

The answer was to change the steering geometry by lowering the inner rear toe link.  I couldn’t get all the correction I wanted without major surgery but I was able to help it out quite a bit with a simple “bolt-in” kit, and that’s what you get with my “Rear-Steer” kit.  When we do a complete geometry upgraded AGS-IRS assembly we move all the rear suspension pick-up points and modify the inner toe-link point to achieve the optimum rear-steer geometry that I’m looking for to get superior handling.

I have seen and heard others (including some of my people in the past) refer to “Rear Bump Steer” kits for the IRS.  Just as a point of clarification, in my view Bump-Steer is a function of front suspension when you hit a bump as you are steering.  At the rear with IRS, its “Roll-Steer” that is the issue because the rear wheels drive, and are not suppose to steer the car.

Either way if you have a ’99-’04 Cobra that has been lowered, not having your rear wheels steer the back of your car the wrong way in the middle of a turn is a good thing.

Kenny

Kenny Brown Rear Steer Kit for ’99-’04 IRS Cobras     KB-49550    $ 179.00