Need help setting up my 1994 GT for autocross

[GeeTeeFiveOh]

You guys are going about it all wrong. You can definitely read up on the basics of what to mod. But, there is no magic recipe on what is 'the best'. It is really the driver's choice.

Most performance mods come from some sort of racing. You see a part on a race car and you want it. Whether you see it in a magazine or on TV, etc. someone sells it to you. And with the Internet, you can search or research anything instantly. You don't have to experience anything, you read what appeals and then you apply it to your car, or even recommend stuff to others.

Well, my analogy is a little different. I did the same thing for years, read magazines or the Internet for my next mod. When I started driving (with NASA), the one thing you pick up right away, is what your car lacks. And you learn that from seat time. Is the problem out back? In the front? While braking? Oversteer and/or under steer? High speed control? Bla bla bla?

So no disrespect to anyone, but reading posts about CC plates and bump steer kits and the best handling mods is just stuff repeated all over the Internet. Actual personal experiences are very few, but most guys/gals do not drive. I really encourage you guys to get out there and do it. Find out what your car needs by explaining a specific problem, not "I want it to handle like a Porsche". There's also the 'nut behind the wheel' element, where the driver mod is probably the best to improve auto-x and lap times.

I guarantee that you put a seasoned driver in a all stock Miata and a inexperienced driver in a Cobra R, that Miata driver will win every time.

I agree with what your saying but reading up and doing "standard" performance upgrade is a good place to start. Especially when it is time for a suspension overhaul after a hard 184,000km, I needed to replace most if not all the suspension components to make it suitable for me as a daily driver and weekend warrior. I had suspension clunks really rough ride bottoming out etc, found one broken front coil spring (close to its seat inside the rubber) control arms would't hold a ball joint and so on.

I plan on getting some serious seat time this summer at the local tracks and I'll go from there. I'm done buying new parts for the car it will be good to go again with the new control arms. Anything parts were talking about now is just to keep in mind for the future and to know what's out there. I will be happy to share with everyone what my car lacks at the track once I go

 

[RichV]

No, that's perfect. Start with the basics, get some good shocks and struts, and go play.

Over on FEP guys would argue that you need 13" Cobra brakes to stop a 13sec car at a drag strip. Then they would put skinnis on, lol. I would argue with them about stock brakes being fine, but no one even knew how to push the brakes to their limit. You just cannot do that on the street, but they didn't get it.

 

[GeeTeeFiveOh]

Unfortunately I'll be using the stock brakes for this season, they are in good condition and stop the car fine. However I
don't think they will take much abuse on the track.

Are there any big brakes that I can take off another ford or Lincoln that would be good performers? My buddy got 6
piston calipers off some Lexus that fits his supra. Anything similar for us?

 

[RichV]

I woild think you don't need it. I road raced with 99-04 GT brakes for years. Never had issues, pads are the key. I just recently went to Wilwood 4 pistons with 13" rotors. And the primary reason was cost of brake pads. Believe it or not, using the pads for Wilwoods will save me a possible $600 in one season. However road racing has much higher speeds than auto-x which help with brake coolers, I bet a regular auto-x person would know better.

Look into Carbotech pads, and flush your brake system with new synthetic fluid.

 

[Gallows]

Look into Carbotech pads, and flush your brake system with new synthetic fluid.

How many races do you run or is it once per season before changing the fluid?

 

[RichV]

Well road racing sees a lot of heat for 20+ minutes up to 5 times per day. I like to do it every 2 race weekends. Complete flush.

 

[twovalveterror]

Just gonna throw this out there to think about: A lot of the road race guys will tell you skip the IRS and stay SRA. The idea of IRS is great, but Ford's attempt at it for the Mustang wasn't the best b/c it's designed to bolt up to the premade mounting points. You can invest in the right parts for the solid rear and end up with a better handling car for the money.
When I did mine, I looked long and hard at the IRS vs SRA issue. I ended up staying away from the IRS for a track car.

I won't argue with IRS vs. SRA handling, as that has been done to death, and it's clear that a fully modified version of either for our cars is very close to the other.

but I would barely be able to buy LCA's for my SRA for what I got my IRS for. and I can confidently say that per dollar, switching to an IRS was the most significant improvement I've made to my car. every dollar is I've spent is in my build thread, you'll see that for the price of LCA's and MAYBE a PHB, I have a fully built IRS lacking only a diff cooler.

I don't think anyone will claim that a factory style 4 link with the possible addition of a PHB would compete with my set up. I hope to back up my words at the track this summer.

 

[RichV]

What did the IRS improve? Street ride? I believe it. On track I think it's a toss up. You won't be able to compare to your old setup, but you'll have a lot of fun for sure.

 

[twovalveterror]

as I said I haven't hit the track with it yet, but along with an improvement in ride, it is much more stable. my favorite on ramp resembles a long (about a half mile) sweeper. at one point in the turn, there is an overpass. at that overpass with the solid axle I had to let off when I hit the expansion joints for fear of losing control, with the IRS I fly right over it without a worry in the world. and there is also the much more subtle addition of mid corner confidence. I can get on the gas earlier and harder and have confidence that the car will do exactly what I want it to.

 

[ReplicaR]

People will argue back and forward, about what's better on mustang (IRS or SRA). Pernally, if you are after complience and feel of the car, I think IRS would probably serve you better in those two ways. Part of that reason is that the two wheels are fully independent from each other (other than sway bar). The other part is the unsprung weight. It is true that IRS as an assumbly weights more than SRA with torque arm and panhard. However, most of that assembly is actually sprung weight that moves with the car. Everything but control arms, axle shafts, and spindles stays with the chassis. On the SRA car however, the entire rear axle torque arm, control arms, and panhard rod are unsprung weight. What that means is that essentially increases the weight of all the moving parts, and they move slower, therefore making the car feel floating in the back

Having said that, as far as absolute grip goes, I don't think I've once said "Man, I wish I had more rear grip". MM rear package is a strong piece that offers a LOT of traction. I've got MM front end as well, and rear still grips harder than front, but I think at this point it has more to do with my weight distribution.

 

[GeeTeeFiveOh]

I'm really liking the MM parts. Installed their front control arms and they are very well made, handling was improved not to mention they look awesome!

Now I think I am done with the suspension for this summer I'll post a picture up soon

 

[GeeTeeFiveOh]

I'm getting a squeak sound when I hit larger bumps such as pulling into a driveway. Its only coming from the driver side which is where the ball joint originally fell out. I re-greased the MM control arm nipples and did not affect the noise. The shocks fell really solid and the handling is great apart from this noise I would be happy. Any ideas what would cause this squeak?

 

[ReplicaR]

It's kinda hard or should I say impossible for someone to just tell you what it could be. If I were you, I'd start troubleshooting by eliminating variables. Try to move components independent from each other. This is the only way you'd be able to see what squeaks. From my experience sway bar bushings usually make the most noise. You can check those as well.

 

[GeeTeeFiveOh]

Good call. you were right on the squeak. While I was there I re-assembled my QA1 coilovers hoping I could get them to make less noise. There was some play in the spring perches so I wrapped the top and bottom spring seat in electrical tape. That got rid of other noises.

I have tubular control arms with poly bushing, thick steeda swaybar and the 250lb front coilovers. This on nitto nt05 tires 35 profile tire. How much NVH should I expect?

It seems pretty rough but it gave me the handling I wanted and I can deal with the harshness if its normal for this setup. Thanks

 

[GeeTeeFiveOh]

I went on a camping trip with the Mustang and loaded about 300lbs of goods in the trunk and back seat. This had the unexpected effect of greatly increasing driving comfort and handling. I find if I am taking a corner that is not perfectly smooth the back end likes to jump around a bit, with the weight the problem is much less. The feel from the front end was also improved.

It's the exact same improvement in ride quality and handling that you would experience from driving my f150 with about 500lbs in the bed vs completely unloaded.

I want to increase the stability without adding the weight. What would you do? Has anyone experienced improvements from added weight? I'm thinking the large difference between front and rear wheel rates is compounding the problem. 250lb spring coilovers in front with ford racing rear springs. Any thoughts?

 

[ReplicaR]

Added weight will never improve anything. The benefits of downforce generated by extra pressure from the weight will always be offset by the drawback of having to deal with more weight under lateral grip. Ride quality improvement you've notices is probably from the reduction of suspension travel. You can achieve same exact thing with better shocks, as firmer valving will slow the suspension movement down to where it should probably be. What suspension do you have so far?

 

[GeeTeeFiveOh]

What suspension do you have so far?

FRONT:

MM caster camber plates
MM control arms with poly bushings
Steeda sway bar with poly bushings
Steeda bumpsteer kit
QA1 double adjustable 250lb coil overs (1/18 clicks bump 2/18 clicks rebound is my set up for street use)

ALIGNMENT:

-1.8 deg camber
5 deg caster
0 deg toe

REAR:

Koni yellow shocks on firmest setting
Ford racing lowering springs (200-300lb linear rate)
Stock GT everything else

 

[RichV]

Rear grip can be affected by a lot of things. I agree with Dmitry on the weight. It's not the weight that makes it feel better, it just feels flatter. But do the same turn twice as fast and I guarantee it will get interesting to say the least. Do you have SFCs?

It looks like you have a decent setup on paper, what tires do you run? Size and type? You can relocate the battery in the back, corner weigh the car where you adjust the coil overs to put more weight on the back tires, increase the size of the front sway bar, and the all out mod is to camber the rear axle, just like you do the fronts.

Are you sensing oversteer or understeer when you run at the limit?

 

[GeeTeeFiveOh]

Rear grip can be affected by a lot of things. I agree with Dmitry on the weight. It's not the weight that makes it feel better, it just feels flatter. But do the same turn twice as fast and I guarantee it will get interesting to say the least. Do you have SFCs?

It looks like you have a decent setup on paper, what tires do you run? Size and type? You can relocate the battery in the back, corner weigh the car where you adjust the coil overs to put more weight on the back tires, increase the size of the front sway bar, and the all out mod is to camber the rear axle, just like you do the fronts.

Are you sensing oversteer or understeer when you run at the limit?

Totally agree on the weight thing also, feels better on the street when I added weight and that's about as far as it goes. I don't have SFC or other chassis stiffening but it is on the list for sure.

WHEEL / TIRE COMBO

18x9 front wheel with 265/35/18 Nitto NT05
18x10 rear with 295/35/18 Nitto NT05

It currently over steers at the limits and I think I need to shorten my front sway bar end links. I've heard of people needing shorter end links with my set but it was mentioned nowhere in any of my instructions. Running stock length end links and they are tight as hell

I've seen those cambered SRA somewhere and thought that was pretty trick however my goal is to put IRS in this thing (already made up my mind) So far put about $200 total into the rear suspension so I cant complain too much. Any other money for the rear end will be saved for the IRS. Rear battery relocation kit is here and will set it up in the near future.

Corner weighting would be great but don't know how to do it on my set up. I helped my buddy corner weigh his race car once but it was way easy because the components where designed for that.

 

[ReplicaR]

I've been thinking about this on the way back home from work, and here is something I came up with. When you loaded up the car, you increased weight of the vehicle. To achieve the same kind of stiffness and suspension travel characteristics as you did in a lighter car, you would have to bump the spring rate to compensate for the added weight, which you didn't. If you look at the spring rate to chassis weight, you will see that the spring became relatively softer. A softer spring is a more compliant spring, therefore better traction over bumps.

Having said that, this does not mean that you get better handling car. All it means is that you just have a more compliant car over a bump. So unless you are running your mustang in Baja 1000, I'd stick to the regular programming of less weight, and stiffer springs.