A good place to start would be about double the front spring rate and probably about the same for the rear rate as well. Then I'd focus on squaring up the tire combo.

 

Not an expert on the SN95, but a 255 front and a 315 rear is a pretty extreme stagger that would cause the rear end to have a lot more grip than the front. All the fast autox guys I know, and in particular one well set up new edge Cobra on slicks, runs a square tire setup. Even the national level S550 guys in Street class, which requires us to run stock width wheels, run square tires despite having wider rear wheels. Now I'm no SN95 expert, but I'm assuming the MM shocks up front have a lot more damping than the meh GR2s in the rear, and if the front compression is much higher, when the weight transfers to the side of the car on turn in, the front end will tend to wash out since the rear will load up first and dig in.

Finally, the roll you're feeling is cause the 200# front springs are relatively soft compared to the 500#+ springs others like Whiskey seem to be running. I'll wait for him to chime in on spring rates, but it is possible to run more than 200# up front and still maintain a decent street ride while having a well balanced and fun to drive autox car. Hope this helps, but going to a square tire would make the biggest difference.

Guess he did chime in right as I was making my post - go Whiskey!

 

I emailed jack at mm to see what he has to say.
I wonder what a 250-12 or 300-12 would ride like on the street?
I also think a larger rear seat bar may help aide the car from pushing in the corners with the staggered tire set up.
Or I should just buy another set of wheels for autox, lol

 

If the dampers can handle the springs, it'll firm but not harsh. IE: All the chassis movements go straight into the body of the occupants, but that movement is far less harsh than even an OEM setup with lowering springs. I daily drove my S197 with 550lbs/in front springs and 275lbs/in rear springs. It was firm, but not harsh. Eschantra can confirm it did handle well too!

Thing is, the SN95 front suspension geometry is awful. The rear suspension geometry, is also quite awful. Try and find iRoush's Youtube videos of the front suspension. He was running like 400lbs/in front springs on his MM coilovers and it looked like he was running stock springs there was so much movement of the LCA. All that movement on a strut suspension is bad, to an extent. 400lbs/in would be a starting point for me.

Hell, on my S550 (when it arrives) when I go to coilovers I'll probably go back to 550lbs/in front springs and whatever it takes to balance those front springs out back. Smallest rear bar possible.

 

Agreed. Definitely stiffen up the spring rates. and get the tires square. most people I see on street tires are running 275's on all fours. stupid newbie me only bought 265's
I put on the H&R Super Race springs and was worried about a harsh ride but it was actually a lot better then worn out soft stock springs. firm not harsh. I drive mine on the rode a lot too.

 

I might consider trying out like a 300x12" spring

 

I'm running 12" 200 lb. springs in the front of my car as well. Just keep in mind, if you increase the wheel rate in the front, then you would also need to increase the wheel rate in the rear to maintain level ride. Jack @ MM reccomended I install MM Torque Arm springs in the rear if I wanted to go with stiffer rates in the front.

 

Have you autocrossed the car with those springs ?

 

Yeah, the 200x12 is okay for the street, but I might try going to a 250 or 300.
I would imagine 300 feels not so good on the street though.

 

300 is soft,


i was on 400/300 and i thought that was soft, now im on 500/400 still think its soft. I need to swap these MM sport dampers for MM3 race.

 

anyone have any advice?
I don't plan on going to a panhard setup or anything, too much money for my taste, for a car that is going to be autocrossed a few times a year.

I've been upgrading my '04 GT DD for autocrossing and I've learned a bunch from the MM guys. Springs and tires is covered well in comments above but there a couple things that jump out for me.

1.) Poly bushings in a tubular UCAs is a problem. Unless you go Torque Arm and remove the UCAs the bushings and arms need to be complaint enough to compensate for the binding in the crap four link rear end. Could even damage the chassis mounting points with significant body roll.

2.) Last upgrade on my car was the MM Panhard Bar. Really improved the behavior of the back end for both street and track. UCAs don't take lateral loads any more. Fairly big project but if you've done the front cross member install it should be no big deal.

Lastly I'm currently working on something nobody I could find makes for our cars. Sold bearing style front sway bar links. The urethane donuts in the stock links have to compress by design before fully loading the sway bar. I designed spherical bearing rod end (Heim Joint) links for my 1970 Mustang when I first got into autocrossing so I'm doing it again for my '04. Less body roll and better transient response. All the later Mustangs appear to have some kind of solid bearing style links as part of Ford design upgrades. But the rod ends look way more cool anyway. I'll take pics when its done.

 

Bumping this back up.
Picked up a set of bilstein hds and a rear coilover kit.
I already emailed jack, but what rear spring rate would you guys recommend?
I still think I need to go way stiffer in the front though.
My car dives during braking really bad.

 

With coilovers in the rear? 550lbs/in up front and probably 225/250 out back would be at the upper end of what I'd consider for a street driven car with a serious emphasis on autocross duty. If you were in the stock location out back, I'd say stiffer, but with coilovers you gain a lot of motion ratio and don't need as much spring rate. Up front, you have to remember you are fighting some really "awesome" geometry from Ford with regards to camber curve and if I'm at 550 on an S197, I can only imagine 550 is going to probably still not be enough to get the front tires happy enough!

 

I do believe mm doesn't recommend anything over 300lb on regular bilsteins. Just curious as to what spring rate would match the front? I have no idea where to start with rear spring rates.
I think I may try a 275 or 300 12" spring in the front

 

You know what will be an awesome set up - SLA type in front (e.g. from Griggs racing) and IRS from S550 in rear. Now that will be a real sports car. Will not need stupid spring rates or ridiculous size tires. Technically you can do that if you have money.

 

Don't have that kind of money. I've been doing some math on wheel rates trying to figure out a setup. I'll post it up later.

 

I like to do auto-x myself. Run pretty well in my group with NASA (usually top 3) and I could probably pull off 1st every week if I had a manual trans.

Currently I am running the Eibach Pro-street Coil-overs and Eibach 35mm swaybar in the front and 24mm rear. I get compliments about how neutral the car is. I also run a "square" tire setup. Nitto NT05 275/40/17s all the way around. Cobra swapped brakes and Hawk HP+ pads. The car will push in a corner if I brake too late but otherwise it ain't bad. Keep in mind though my engine is mostly stock compared to yours.

 

Any idea what the spring rates are that come with the eibach coilovers are ?

Edit: actually nvm. AM lists them as 200 front 250 rear. Which is odd, usually the front has a higher rate.
But then again it looks like the eibach kit isn't a true coilover as it looks like it uses an adjustable perch in the stock location. Am I correct ?

And here is my wheel rate math

Currently my setup is 180# and about 157# rear (that is at ful load though as those are progressive springs)

 

Any idea what the spring rates are that come with the eibach coilovers are ?

Edit: actually nvm. AM lists them as 200 front 250 rear. Which is odd, usually the front has a higher rate.
But then again it looks like the eibach kit isn't a true coilover as it looks like it uses an adjustable perch in the stock location. Am I correct ?

I honestly couldn't tell you. It isn't compressed so to speak like in a car that came with a coilover setup. You can safely disassemble the entire setup without any special tools. There rear is still a spring and strut setup though with that kit. Idk if you can really get a true coil-over setup for our cars but KW offers a pretty good setup but you will spend a lot of money for it.

I don't know if the spring rate is correct but I imagine the big sway bar helps too.

 

Maximum motorsports rear coilover kit is a true rear coilover.
I almost bought a set of rear kw's but the guy wanted like $550 for them

 

I would have tried to talk him down I think. Guess it depends on how used they were. All these numbers are making me want to know what my springs are really rated at. 200 doesn't seem like enough to me with everyone saying 500 and 600 but yet I get around the track just fine.

 

I'd think they are higher than that but who knows.

I'm still waiting for MM to email me back, but I think I'm gonna go to a 275 or 300 front spring and a 200ish rear spring