gt37vgt

remember the rears are divided by something like 1.65 to get the wheel rate so I wouldn't go much higher than 250 front and 450 rear for a dual purpose car without fancy coil overs.

Scootin159

yeah.... thanks for pointing that out, for some reason I just wrote it out wrong.

Scootin159

You are correct (I forget the number, but there is a ratio), but also remember there is a ratio for the front's as well. It's much closer to 1:1 in the front than the rear, but not exact.

95ONE

Interesting. Didn't kow this. (upgrading next week)

ehall

Ideal = no such thing.
Telling you what is ideal is like trying to give you a golf lesson over the internet without any video.

Funn944

I have the Ground Control Koni's, 250lb fronts springs, and camber plates. Front strut bar and Weltmiester Stage Two sways front and rear. Stock indexed torsion bars in the rear, but lowered as far as it will go with the eccentrics. I just talked to the guys at Ground Control. They felt that for a street car with occaisional track use the rear coil overs wouldn't buy me much. I run 255/50/16 G-Force Sports in the rear, 245/50/16 in the front. Rides pretty firm for the street, but not harsh, handles pretty damn well on the track too.

Just throwing some info out there.

ehall

I run 500/650 f/r on the street on my 951. It's my daily driver. No t-bars

IanM

I put together a bit of a database, based on front to rear effective spring rate ratios from my car and from my friends cars, and using my experience and feedback from them. As I said, there are other factors, including tire sizes, alignment settings, swaybars, etc.

BTW, the 0.56 conversion factor for rear coilover effective spring rates is from Paragon Products. Other people use a slightly different number, I'm not sure what the "correct" number is.

My personal experience is that a front/rear effective ratio of about 1.1 gives slight understeer to neutral. My old setup was about 1.06 and my new setup is 1.17. Some racers running super stiff spring rates and coilovers swear by a ratio of 1.25 (looking at ehall's spring rates, his ratio is 1.24). But many of these cars are typically lightened (lots of times most weight comes out of the back) and may run equal size front and rear tires and very aggressive camber. For my "street" settings and normal staggered tires, I think 1.25 would result in severe understeer. I have driven cars that run ratios of 0.9 and less, and they tend to oversteer a bit, but can be setup to be very controllable and fast. Personally I like something around 1.1 - I find it to be very safe and fast on the track, I can easily counteract any turn-in understeer with the throttle. In autocross I do get a bit too much understeer on really tight corners, but my intention has not been to create an autocross car. Again, I could counteract that with wider front tires and 3 degrees of negative front camber.

MM951

thats why I put ideal in quotation marks

ehall

Yeah I understand why, but it's impossible to answer. I don't drive your roads and only you know what feels just right to you. You live on roads with snow affected pot holes, I presume. I don't.
I run 16" wheels. That adds a bit of cushion compared to say, 18" wheels. There are just a TON of variables, but most important is your own personal taste for the feel of the car.
Also, this stuff is dependent upon the condition and compositon of your bushings.
I'm just saying that this is a REALLY difficult decision to make.
Get the dampers right. Springs are cheap. They aren't that tough to change, if you don't like your set up, but damper changes are a project.

jakery

my $0.02

I'm running 500f/600r (torsion deleted)
Car weighs 2850lbs dry

It is GREAT for smooth twisties & passing on blind turns, but i dread hitting bridge seams.

Next springs will be 400f/500r

Oh, with 600# in the rear & 375hp-ish i still have a good bit of rear squat off the line & into second.

95ONE

I was alarmed at how much weigth I had taken out of the rear and under went a large project to start taking out as much as I could out of the front to counter act. That wasn't easy. So, yeah. The rear of the car is pretty light.

But to get Say a 1:1 ratio (evenly balanced car) I would have to look at it like this....

500 front x .96 (effective) = 480
850 rear x .56 (effective) = 476

I gotta tell you. That seems way off.

MM951

Thanks for all the imput guys..

I bought these guys w/ 450# rear springs

http://www.ground-control-store.com/.../II=749/CA=159

The guys at ground control told me since I have recently rebuilt front koni adjustables + gc coilover kit I should just get the matching front springs (300#) and see how the car feels. Pretty nice they weren't trying to sell me on something I didn't need

FWIW, I do a decent amount of driving on the tacconic state parkway (which has gotten alot better in recent years) and there are some crappy sections of road around here, but I already avoid them.. I'll report on how I like em once I get them. Next up is weltmeister or 968 m030 sway bars

IanM

I understand the front total to effective spring rate conversion to be 0.9 not 0.96. So a 500# front spring would be 450# effective. A rear 800# spring would give you 448# effective.

It does seem that a lot of people run a ratio >1.0 and up to 1.25, especially when running higher than 400# front springs. As I said, I think part of the reason is that the people running the super stiff springs have also lightened the back of their cars (which would allow for using softer rates in rear) and wider tires/more camber in front (less understeer, allowing stiffer front springs before understeer). My current setup (400#/550#) gives a ratio of 1.17. If using 500# front springs, that would give about 675# in back. The way my car is setup, I'd probably run a 700# rear spring if I was going with 500# front.

Mike - 300# front and 450# rear sounds great.

RPHARRIS

I like 300lb up-front matched with 28mm torsion bars with koni single adjustables all around. You won't be dominating any track days or autocross's with this setup but it works great for daily driving and mountain roads.