Autocross build out for my 2003 Cobra

bubblehead93

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More to follow... to include pictures....

Putting this marker on the forum for my build... there has been many builds over the years with this car since I'm the original owner...

When I was stationed in Guam, was introduced to and started doing a lot of auto-x... came back to the states about five years ago and life happened, so I'm starting to get back into auto-x, well actually, going full throttle on what will be a max effort car... i'm sure the driver will be what ultimately holds this car back from its potential... plus I like fabrication/fiddling, so there you go...

Right now I'm trying to see how far I can take the front MacPherson strut setup before eventually considering a SLA setup.

In Guam they did not care about UTQG or what class anyone's car fit in, it was just a bunch of enthusiasts showing up, doing a bunch of runs (until it got dark), and working the course between those runs... I was running a staggered NT01 setup on 17x9 and 17x10.5 FR-500 replica wheels with a 1/2" spacer in the rear with MM MM2 coil-overs in all four corners. It was a bunch of fun but not a legal setup for auto-x events stateside.

The goal now is to run a square setup, identical front/rear track width built around Falken Azenis RT660 315/30R18s (200 UCQG) at all four corners... utilizing 18x10.5 wheels...

Unless I want 1.5" of tire sticking out on each side in the front then some front fender flaring is in order. In addition I wanted to do a couple things that would allow air to flow better out of the front fender area...

By now most of you are asking, great, show me some pictures... I will not disappoint, more to follow... for right now I'm going to stop here and I'll have a bigger post(s) this weekend with lots of new car part porn and information for consideration if you ever want to do something similar...

Thanks for tagging along on the journey...
 

bubblehead93

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So the goal of this build for autocross is to fit 315 spec rubber at all four corners...

For starters I installed my rear tires on the front...

FB_IMG_1644763457055.jpg


These 17x10.5 FR500 replicas I sourced from AM years ago have 6.8" of backspacing... 27 mm positive offset...

The 17x9 rims I had been running had 6.2" of backspace, 30 mm positive offset...

So 5/8" of wheel spacer later, the rear tire/rims were now fronts...

More to follow...
 

bubblehead93

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200 UCQG rubber requires a shift to 18" rims, there are simply no offerings... However I am going to maintain a square set of NT01s (100 UCQG) on 17x10.5 for track event purposes...

I'm always keen to minimize required wheel spacers to achieve proper wheel offset... So the hunt for an appropriate wheel began...

I managed to find a Chinese wheel branded under Aodhan... 18x10.5 5x114.3 with +15 offset, with a 73.1 mm hub bore... This works out to 6.34" backspace... The 73.1 mm bore size also necessitates the use of 70.5 mm / 73.1 mm hub adapter rings, readily available, got a set from AM...

FB_IMG_1644763468134.jpg


Picture also shows that some significant surgery is in progress...
 

bubblehead93

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Long term I'll purchase a set of custom flow formed wheels once I sort the setup out... the price was right on these, about $800... the custom wheels will be 2-3 times that at least...
 

bubblehead93

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I have a set of 3/16" hub centric spacers coming for the front (versus the 1/4" ones currently installed, might seem OCD but you want the tire as deep in the wheel well as possible while still clearing the coil-over spring/collar and sway bar... the further the tire sticks out the less room you have with fender clearance... so i'll take every 1/16" i can get... I might still go with a 1/8" spacer once I have final ride height set, if there is clearance...
 

CobraBob

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I cringed a bit when I saw the cutting and welding you did on the front fenders. LOL. But I totally get what you're doing and why. Just hate to see a nice Terminator getting cut. I'll definitely follow your build and hopefully hear some good autocross news from you later this year. (y)
 

bubblehead93

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lost a lot of sleep before finally deciding this was the right way to go... but there is nothing special about 99-04 mustang front fenders... luckily, no need to do anything to the rear quarters, can hit desired track width with the entire tucked under the rear fenders... no need to flare the rears... besides that would be a whole other level of PITA bodywork...

Truth in advertising, the car is autocross ready... it has the whole MM catalog on it, both front and rear, this step of the build is about fitting the 315/30-18s at all four corners and setting up the wheel alignment for full autocross send... I'll talk more about that as well as current spring selection, sway bar, etc....

If there is interest can cover all of the existing modifications...

Have a great Monday...
 
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98 svt

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Glad you decided to start a thread.i also was a bit shocked with the work on the OEM fender. Why not just use a couple extra fenders? They will need paint anyway.
 

bubblehead93

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I have so much in the way of take-off parts laying around between my various cars and trucks, not looking to adding a pair of fenders to the parts pile....
 

DCguy

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Long term I'll purchase a set of custom flow formed wheels once I sort the setup out... the price was right on these, about $800... the custom wheels will be 2-3 times that at least...
You could just do the typical RPF1 setup in 10.5 square. They are a +15 offset so should do the job of clearing the springs well...they are also deep bore so fitting bigger calipers is not an issue. This year they are also releasing the RPF1 "RS" anniv edition in an 18x10 and 18x11 in some fairly aggressive offsets....highly considering them for mine.

I'd be very weary running cast "reps" on a 315 slick.....you've seen the stories/pictures.

Curious what is your spring rate and coil spring length in the front end from MM? I went with a 400lb 10in spring/RA2 strut for street/occasional HPDE.
 

bubblehead93

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i run a 400 lb 10 inch on a MM MM2 front strut with the stock sway bar...

Definitely would go forged before time trial/road course events to enable really attacking the corners to include the curbs...

Really any wheel has a "shelf life" just comes earlier for cast than it does for flow formed then it does for forged... at some point any wheel needs to be retired from a fatigue/work hardening perspective...

Have done a lot of autocross on my old cast replica staggered wheel setup with NT01s... not too worried using these wheels for autocross... again HPDE, time attack, and other track events... whole different animal...

These wheels are just a stepping stone before going with a forged wheel...

The Enkei's are just flow formed right (MAT Technology)?
 

13COBRA

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ouch... i love my zinc yellow, of course I like lime gold on my 67 as well, so my judgement may be in question.... lol

Haha I don't mind it, but not a favorite.

When are you hoping to have this monster done?
 

bubblehead93

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hopefully metal work done next weekend...

Re-alignment hopefully as well, smart string/longacre caster/camber gage garage style...

a bunch of road testing... then final body work and paint for the fenders... so end of March at the latest...
 

13COBRA

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hopefully metal work done next weekend...

Re-alignment hopefully as well, smart string/longacre caster/camber gage garage style...

a bunch of road testing... then final body work and paint for the fenders... so end of March at the latest...

That's awesome. Please make sure to keep us updated.

In the mean time, do you have any recorded footage of your auto-x history?
 

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