Suspension Upgrade for Auto Cross

Hey guys! I'm looking to get into autocross with my 04 Cobra, and am looking for some of the better ideas for suspension upgrades. I come from a 2011 STI which was easily, coilovers and sway bars and it would hug the road like no other. But I'm still trying to learn this whole IRS beast and figure out what would be the most helpful.

Currently, I'm looking into a set of lowering springs, but past that I'm not sure what would be helpful an what wouldnt. The car has 37k miles and everything suspension wise is currently stock.

Subframe connectors should be first if the car doesn't already have them. Then replace the bushings in the IRS. Those will get rid of the disconnected feeling the IRS can have. From there I would say it depends on your budget and if you have to follow any rules. You could go all out with coilovers and tubular K members. But they may not be allowed in the class you want to run in.

Check out fulltiltboogieracing.com. They have some good info and products.

I'll have to give them a look thank you! I'm about to get some HR Race springs, MM IRS bushings, and MM Subframe connectors and then going to go from there and see where things take me

I'd look into the Stifflers stuff for sub frame connectors. I have their connectors with the jacking rails and love them. The rails are really handy with a lowered car.

Your best course for mods if you want to do really well at autocross is remove any existing mods you have, sell those mods, sell the Cobra, buy the STI back.

Just kidding... but seriously.

I'm not much help to be honest. I actually want to autocross my terribly inefficient Cobra quite a bit... for fun and all. I could regurgitate some info, but your best bet is to look back at the 15 years of history for these cars stored right on this site. I have done some searches in the past, there should be a wealth of knowledge for your car, especially in the autocross portion of this forum.
I like Google for searching, try using this search string on google: autocross "03 cobra" site:svtperformance.com

Full suspension here, I run away from sti’s in canyon runs. I’ve run away from average drivers in z06’s and Porsche’s as well. Embarrassed a guy in a lotus evora, on and on. Driver mod as in good footwork skills to get rotation from using al 3 pedals well on corner entry, and a Parnelli Jones esc competently settable car will do excellent. There are YouTube videos of a worked up 2000 cobra R lapping with and passing a Porsche Carerra GT. Not a 911, the 2005 mid engine $400k supercar porsche.

Anyways, here’s some feedback

1, 2 and 3 are all honestly one big step/commitment.

1. Driver mod. Seat time, practice practice practice on what you have now.

2. Take driving lessons from an instructor while doing this.

3. Have competent tires, pads, brake fluid, and rotors. (not insane stuff, just nothing with worn edges or cupping, nothing overly used etc. Nice healthy fresh wear items). When you get a good feel for driving it stock, get a moderately agrressive alignment. Something around -1.75° up front and -.75 to -1° rear as well as zero’d toe and up to 5.25° of caster, but usually 4.5 to 4.75°. Excessive Caster will make it feel like it has a little rear steer.

Now for mods:

Get light weight rims very first. Unsprung weight reduction is the best thing you can do. Tsw makes a bunch of rotary forged wheels. My 18x9/10’s are 22 and 24lbs. My factory 17x9’s were 30lbs each. Each lbs of unsprung weight is similar to dropping 10lbs of sprung weight. Sprung weight could be the actual floor plan of the car for example, the wheel and brake are out board of the suspension so they unsprung.

A. Start with stifflers subframe connectors.

B. Save and do the entire full tilt boogie racing 5001a kit with tie rods and full bushings. The MM stuff is good, but the ftbr kit has been shown to be better

C. From there save for an MM kmember, steering shaft, camber plates and full coil overs. I run the stock geometry mm kmember and 425/550# springs (if I recall correct) with Koni single adjustables. I have an aluminum engine block and the kmember so I went with softer front springs than others have chosen.

D. Get an auburn differential if you won’t be going north of 500whp. If you will, you’ll have to make do with a Detroit trutrac. Also can upgrade axles at this stage to DSS units, etc. 3.73 is a great autocross gear as well.

E. Better brakes. Brakeman kit is best for autocross because it’s very light, and much more brake than you’ll ever need for 60mph maximum speeds. Ditching unsprung weight is crucial.

F. Could try an agent 47 sla front suspension or a Griggs sla. Very expensive, and not as streetable. There is a definite reason why these units are the top performing systems in aix. Mcphaerson can’t compete with the flexibility and optimization of an sla

Racebronco is a member on this site who can give you much better info as he has raced his cobra a lot for a decade or so.

tt335ci03cobra said:

Full suspension here, I run away from sti’s in canyon runs. I’ve run away from average drivers in z06’s and Porsche’s as well. Embarrassed a guy in a lotus evora, on and on. Driver mod and a parnelli Johns esc competent car will do excellent. There are YouTube videos of a worked up 2000 cobra R lapping with and passing a Porsche Carerra GT. Not a 911, the 2005 mid engine $400k supercar porsche.

Anyways, here’s some feedback

1, 2 and 3 are all honestly one big step/commitment.

1. Driver mod. Seat time, practice practice practice on what you have now.

2. Take driving lessons from an instructor while doing this.

3. Have competent tires, pads, brake fluid, and rotors. (not insane stuff, just nothing with worn edges or cupping, nothing overly used etc. Nice healthy fresh wear items). When you get a good feel for driving it stock, get a moderately agrressive alignment. Something around -1.75° up front and -.75 to -1° rear as well as zero’d toe and up to 5.25° of caster, but usually 4.5 to 4.75°. Excessive Caster will make it feel like it has a little rear steer.

Now for mods:

Get light weight rims very first. Unsprung weight reduction is the best thing you can do. Tsw makes a bunch of rotary forged wheels. My 18x9/10’s are 22 and 24lbs. My factory 17x9’s were 30lbs each. Each lbs of unsprung weight is similar to dropping 10lbs of sprung weight. Sprung weight could be the actual floor plan of the car for example, the wheel and brake are out board of the suspension so they unsprung.

A. Start with stifflers subframe connectors.

B. Save and do the entire full tilt boogie racing 5001a kit with tie rods and full bushings. The MM stuff is good, but the ftbr kit has been shown to be better

C. From there save for an MM kmember, steering shaft, camber plates and full coil overs. I run the stock geometry mm kmember and 425/550# springs (if I recall correct) with Koni single adjustables. I have an aluminum engine block and the kmember so I went with softer front springs than others have chosen.

D. Get an auburn differential if you won’t be going north of 500whp. If you will, you’ll have to make do with a Detroit trutrac. Also can upgrade axles at this stage to DSS units, etc. 3.73 is a great autocross gear as well.

E. Better brakes. Brakeman kit is best for autocross because it’s very light, and much more brake than you’ll ever need for 60mph maximum speeds. Ditching unsprung weight is crucial.

F. Could try an agent 47 sla front suspension or a Griggs sla. Very expensive, and not as streetable.

Racebronco is a member on this site who can give you much better info as he has raced his cobra a lot for a decade or so.

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Thank you very much for all this info! I'm in the process of looking up driving instructors/classes in my area now actually to start getting more wheel time.

And I will begin looking into that mod path! I appreciate your post a lot!

tt335ci03cobra said:

F. Could try an agent 47 sla front suspension or a Griggs sla. Very expensive, and not as streetable.

Click to expand...

Curious why you feel the Griggs SLA is not as streetable? I’ve had no issues.


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94 Cobra R said:

Curious why you feel the Griggs SLA is not as streetable? I’ve had no issues.


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I’d have no issue with it, nor would any gearhead. People like my aunt or second cousin would be terribly annoyed by road noise and direct feel.

I eat rare steaks and want to learn how to hunt with a bow and arrow so a suspension free of rubber isolators or noise dampeners does zero to phase my commute. For some people though, if it’s louder than stock they flip out

tt335ci03cobra said:

I’d have no issue with it, nor would any gearhead. People like my aunt or second cousin would be terribly annoyed by road noise and direct feel.

I eat rare steaks and want to learn how to hunt with a bow and arrow so a suspension free of rubber isolators or noise dampeners does zero to phase my commute. For some people though, if it’s louder than stock they flip out

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Ahh, ok, I see where you're coming from. Yes, NVH is a little higher, LOL. Archery hunting is great, definitely recommend it, as would I recommend a good Griggs SLA Ride on!

94 Cobra R said:

Ahh, ok, I see where you're coming from. Yes, NVH is a little higher, LOL. Archery hunting is great, definitely recommend it, as would I recommend a good Griggs SLA Ride on!

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I really want to switch to an sla on my car. Even having to replumb my hot side wouldn’t be a big deterrent.

If I can get an sla upfront, and some fabricated fender flares to fit a healthy 315 up front to match the rear, I’d be very happy. The car is never going to be as balanced as a gt350r or even a boss 302ls (maybe it could) but it would be a very good driving new edge

94, do you have any threads comparing before and after or timeline of your sla build?

tt335ci03cobra said:

94, do you have any threads comparing before and after or timeline of your sla build?

Click to expand...

Sorry buddy. When I bought this Terminator, it already had the full Griggs World Challenge on it, front and back. (costs of suspension work actually equalled what I paid for the car!)

I will say this: I've never ever owned or even been in a Mustang that grips like this one. Whether around a track, on the street or in a straight line. And that's with 606rwhp. But, you def increase the NVH.

94 Cobra R said:

Sorry buddy. When I bought this Terminator, it already had the full Griggs World Challenge on it, front and back. (costs of suspension work actually equalled what I paid for the car!)

I will say this: I've never ever owned or even been in a Mustang that grips like this one. Whether around a track, on the street or in a straight line. And that's with 606rwhp. But, you def increase the NVH.

Click to expand...

Very nicely done, can you pm me some info on the car? If you have some images and lap times I’d love to get your feedback on the experiences with the car. Thanks

Tires, Shocks, Swaybars, rack bushings, Springs, Subframe Connectors, Fulltilt Boogie or MM IRS Bushings. In that order.

If you don’t drive the car a lot you can put a aggressive alignment on the car and play with the rear toe. (I just run SVT preferred alignment)

If you do SCCA events pay attention to what modifications place you in a different class. I think springs and SFC will do that.

These cars are sloppy upfront and have LOTS of understeer that can quickly turn into oversteer if your not smooth with throttle. Lots of body roll too. Here is a picture of my body roll on stock shocks, bars and H&R springs.

Stopping by to say I like where this thread is going . I too am trying to set up my cobra to be a corner carver and I also own a STI lol. Learned some things reading through this thread!

tt335ci03cobra said:

Very nicely done, can you pm me some info on the car? If you have some images and lap times I’d love to get your feedback on the experiences with the car. Thanks

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Sorry! For some reason, never got a notification about a reply!

I’ll get a PM over to you...


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