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Discussion Starter #1
I am looking to upgrade from my current 325/225 spring and Bilstein HD strut/shock setup to the race valved Bilsteins and stiffer springs.

My car weighs about 3400 with me in it, and is about 59/41 for weight split because of the 351W with iron heads. I mentioned that I was thinking about running 425 springs in the front cause a guy at the track with a 95 Cobra R had them, and he mentioned that 475's would be an aggressive track setup.

I only drive the car a few hundred miles a year in the summer, plus 3 or 4 track events. Street manners aren't a big concern since i don't drive it on the road very much. Is anyone running 475's up front? How does it ride?
 

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I have 475s in the front.

It is really stiff and I find myself trying to avoid incredibly rough terran like manhole covers.
 

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Discussion Starter #3
Maybe I will just go up to the 425's then and see how I like that. It will still be a large change over what I am currently running.
 

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I'd be more concerned with going to a 375# rear spring...in effect, you're raising the rear wheel rate a bunch more, as the motion ratios are significantly different f/r...I'm also not sure why you think running that much spring is needed?
 

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I agree with tigerdrvr...375 sounds a little stiff.

I am running 450/300. I rarely drive the street, but I wouldnt say 450 is too stiff. Maybe I've just gotten used to it.
 

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so what would some consider a good spring rate for the fronts for the street? im currently @ 325...was considering stiffening it up slightly with a 350 or 375 spring...
 

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I'll toss my crap out there...

375 fronts with 300 rears on Bilstein MM Sport valved dampers.

I find the ride a little harsh, but I honestly attribute that to the Azenis tires in 35 series and 30 series sidewall tires.

However, it passes the "Girlfriend test" and she even asks if we can take it on trips when it's nice outside. Go figure.
 

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I ran 475lb. fronts and 375lb. rears on my fox with koni DA's up front and MM bilsteins rear. The rear springs were WAY too stiff, I would've gone with 275's or 300's instead. The car was barely heavy enough to compress the rear springs more than an inch or so at rest, had a lot of problems with the rear springs unloading during heavy braking and on corner exit.
 

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But let me add to my 475# front springs. . . .


It is REALLY fun to drive and you can really take advantage of some entrance and exit ramps.
 

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Discussion Starter #11
The only reason I was considering 375 rears is because one of the guys at MM said they recommend a 100lb/in lighter rear spring compared to the front spring. My current combo is 325/225. The rear probably isn't too bad, but the fronts are too soft for open track use, the car rolls over onto the outside front wheel.

I asked about bigger front bars and they recomended running heavier springs instead.
 

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The only reason I was considering 375 rears is because one of the guys at MM said they recommend a 100lb/in lighter rear spring compared to the front spring. My current combo is 325/225. The rear probably isn't too bad, but the fronts are too soft for open track use, the car rolls over onto the outside front wheel.

I asked about bigger front bars and they recomended running heavier springs instead.
That's kind of interesting, the "100lb/in lighter in the rear" rule of thumb... As I understand it, a Fox/SN converted to coil overs has approx. .9f/1.1r motion ratios, so that would indicate, for every additional 1lb/in in spring rate, the rear picks up nearly 20% more wheel rate...unless I'm doing my math wrong, again...
 

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I was also told/made aware of the "100lb spring rate rule of thumb front to back" statement.

I prefer to have a car setup more for autocross over open track, which is why I have the marginally higher rear rate spring. Couple that with the fact that the car really has no horsepower so this helps me rotate the car with the gas pedal when needed.

The MM adjustable rear swaybar i'm finding out is just pure awesomeness. Glad I have that piece.
 

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I have 500's up front with rod ends for swaybar links. It rides stiff, but the swaybar links made a bigger ride impact than going from 400->500 lb springs. My car was 2950 lbs and 54% front weight when I last drove it on the street. I run 500 lb conventional springs on the rear (roughly equivalent to a 250 lb coil over) with a 9.5" panhard bar height and the car is pretty well balanced.

Justin
 

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I was also told/made aware of the "100lb spring rate rule of thumb front to back" statement.

I just don't get making a linear assumption from a non-linear relationship.

E.G. at 375f/275r, front wheel rate is 337.5 and rear is 302.5 (using MM's given motion ratios for their coilover locations). The rear wheel rate is approx 89.5% of the front. Going to a 475f spring rate and using the "100lb/in difference f/r" indicates a 375r spring. Using the same leverage factor, I come up with 427.5 front and 412.5 rear wheel rates...or, rear equals 96.5% of front. I'm no mathematician or engineer, but I'd have to guess that would have a significant impact of f/r balance and promote oversteer.
 

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I'm probably the dumbest person in this section, so I'm just going by what MM has told me/suggested. (why I run NON-adjustable dampers. ;) )
 

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I'm probably the dumbest person in this section, so I'm just going by what MM has told me/suggested. (why I run NON-adjustable dampers. ;) )
I might give you a run for the "dumbest" prize, but I'm not afraid of adjustable dampers...:king:

I'm not saying that MM is "wrong", if that is what they suggest (the 100lb difference as a rule of thumb), hell, I don't know...I'm just saying it doesn't make any sense to me.
 

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I might give you a run for the "dumbest" prize, but I'm not afraid of adjustable dampers...:king:

I'm not saying that MM is "wrong", if that is what they suggest (the 100lb difference as a rule of thumb), hell, I don't know...I'm just saying it doesn't make any sense to me.
It doesn't make any sense to me to run a softer front swaybar....but I did it because they said to(and smarter people on here said to as well). :(

I really hope MM doesn't start selling muffler bearings.... :crying:
 

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It doesn't make any sense to me to run a softer front swaybar....but I did it because they said to(and smarter people on here said to as well). :(

I really hope MM doesn't start selling muffler bearings.... :crying:

Well...if you said your car was pushing or something, then someone might say something like, "hey, maybe you might try a softer front bar"...makes sense, to me.

But, the f/r spring deal (constant at 100lb difference), I don't understand.
 

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I'm getting 400lb springs with my granatelli front end with Koni Yellow double adjustable fronts...

What should I be looking into for rear end mods? Car is 100% stock at the moment in the rear..

Anyone know where I can find the information I need to know to determine what setup I need?

Its looking like I'm going to be holding off on my tranny swap and finishing up the suspension before moving on to something else.. :joy:
 
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