Do you think that a 1007lbs. spring rate coilover would oversteer the car.

 

Front, rear, or all 4 corners?

 

Type of car?

Safe to say that if it's any sort of RX-7 and it's not making a ton of downforce then that rate seems very high.

 

1007 lb. spring rate?! I don't know about oversteer, but you'll lose your wig every time you hit a pot hole!

 

1007lbs in the front and 1007lbs. in the rear of the FD

 

Way, way too stiff for an FD, even for track use only. Even on most tracks, you'll be skittering everywhere -- forget street use, the car would be uncontrollable on a typical bumpy road...not to mention that even spring rates = oversteer. I don't think an FD with rates like that would be very pleasant to drive, or even fast on a road course.

 

I've heard of at least one person running 1000 lb/in springs on the front in a dedicated track car, but I agree, that sounds way too stiff to me. You'd have to only run on dry tracks as smooth as glass, otherwise, you wouldn't have any body roll, but you'd be skittering all over the place with every little irregularity in the pavement. And as rynberg said, your rear rates need to be lower than the front or you will be seeing your *** end pass you on every corner.

 

What if you have 895lbs of spring rate coilovers for the front and rear of the FD?

 

Track use only, no rear sway bar - maybe.

 

Why don't you quit looking at track-only coilovers as it's obvious that's not your intended use? For street use, you don't need coilovers, but if you are set on having them, then you need to be looking at more streetable models -- the Tein Flex, the JIC FLT-A2, the Zeal B6. You also need to do more research -- coilovers with equal front/rear spring rates are going to balance the car towards oversteer. Avoid HKS, most Teins, and Apexi, as these designs use equal spring rates that are too high for street driving.

 

holy crap thats ridiculously high. I run 350F and 300R on my 2600 pound FC and its plenty stiff for autox and daily driving... after I put in a race-bucket seat its almost too stiff. I can only imagine breaking parts, flattenning wheels, blowing out shocks and bending chassis pickup points if I were to drive it on the street with springs more than TWICE as stiff! I'm sure it would be great for Speed Touring Car competiton on glass-like roadcourses but not for a streetcar.

The RX7 is not like a Honda Civic where you need 800+ lb springs to be race-stiff... the suspension designs are incredibly different and a 450 pound spring will stiffen the RX7 up a lot more then you might think... it has to do with how close the shocks lower mounting points are to the wheel, this gives them more leverage agianst suspension loads compared to other cars where the shock mounts more inward on the lower arm.