Autocrossing and the 03-04 Cobra IRS...

[drew_shipley]

I've been Auto Crossing my Bullitt (which has an IRS from an 03 Cobra in it). Due to having the IRS in my car I'm currently running in the ESP class. I was looking at suspension upgrades and was looking at doing some IRS bushing upgrades. It seems I have a few options on materials...

1. Poly
2. Delrin
3. Aluminum (only on the differential mounts)

I had originally planned on buying ac427cobra's Bushing Kit, however, I'm having second thoughts due to the fact that the solid differential bushings will bump me up another class into SM (and honestly my car as is isn't in a competitive state for ESP either).

So my main question is how much gain will I see between the Poly, Delrin, and Solid bushings on the Auto Cross? Is it worth the class bump to go with the Aluminum Differential Mount? Are the Delrin bushings really worth the money over the Ploys on the Auto Cross?

 

[red03dave]

I had the delrin MM in my '03 cobra eaton converted '01 cobra and the turn in was way crisper and I felt more feedback in corners but the snapping point for the backend coming around was a very fine line although all the new found instant torque didn't help either. My buddy put poly's in his '04 cobra and (although I haven't driven it) feels pretty close, slight hesitation upon turn in but a little more forgiving in corners. Hope this helps.

 

[TroyV]

What tires are you running?

I'm willing to bet you can spend more cash there and get WAY more bang for your buck.

A set of Hoosier A's driven properly (as in not slid around much) will pay back in spades.

 

[Goindeafonmtx]

I can share my personal experiences here. I autocross my car with a 03 IRS. It has the full bushing kit from Bruce with coilovers front and rear. I run a 375lb spring in the front and a 650lb spring in the rear and RE-01R for tires. I run in the SM class. Unfortunely, I'm usually the only car in the class, so I really don't know what competition is. I also never ran the IRS in stock form, but here is what I can add: the car just feels stable in the corner but then again, I'm comparing it to when it has a SRA. The bushings do increase NVH, but not horrible. I wish I could be of more help. Next time you are in Evansville, just hit me up and you can take the car for a spin. I can sit here all day and try to describe the way it drives, but nothing is better than actually experiencing the car.

Brad.

 

[svt2712]

Just buy the bushings you want to buy. Its not cheatin till you get caught! no seriously though unless you race where the people take it real serious than just put what you want. Plus is this car just going to be ESP or are you going to want to do more things cuz if you do,you will get put in SM. My wife's GT runs in ESP and I run in SM. the big thing that I have found is that no matter what you have done to the car does not matter unless you have full race tires. We can not afford two sets of race tires so we are going to try the new Nitto NTo5's they are a happy medium. Lots of people that we race with have stock car's but race tires and they are fast. Yes you may think that we are slow but i put a hurtin on some so it is not lack of my driver skill. point is i wish i had full race tires to work some people. I disagree with some of SCCA's rules they need to break it up more.

 

[TroyV]

Fully agree.... It is pretty much all about tires.