Ohlins will be more expensive, but I would pay it happily. Are you still using the factory diff? That will have a big role in balance if you upgrade to a clutch unit.

Good point. I have plans on going with a Torsen-type rear diff. I reckon that would govern a slightly softer rear than factory split.

I'm not a quaife fan at all...I prefer clutch type diffs.

So to bring this thread back from the dead.

According to the math I'm coming up with 1100 lb springs up front and 900 lb in the rear for suspension frequencies of 2.35hz (fr) and 2.31hz (rear). As it sits the corner weights are ~900lbs at each front corner and ~700 lbs at each rear corner. Car is used for autox. Will be using the stock spring locations as the rules prohibit going to a true coil over.

Are these too stiff or just right?

370 oem rear is somewhere around .55, if you switch to true type it is closer to .65, our front oem are around .65/.68. I think this measurement is also affected by your tire width as well because the tire is "extending the lever" a bit. Not 100% sure the correct way to calculate where to measure to, but common sense sort of tells you that if you put a wider tire on it is going to make this number a tad lower, hence needing a stiffer spring.

I still daily my car but have finally settled on 12k/10k full stiff stillen front and I ended up pulling the rear bar completely. I think 12k/ 8 or 9K with a rear OEM bar would probably be nearly equivalent. For autoX nice smooth surface you could definitely go higher, but I think I am at or near the limit of what you would want to DD.

That's a little soft by some standards, but our tracks in socal are not very smooth for the most part, have a lot of elevation changes, and I still need to get over those damn bumps in my office's parking lot.

I started at 1100/650 (Hotchkis front and rear bars) and it's in the ballpark. Without a rear bar I'd probably start at 1100/800. That that's with skinny little 255 street tires on 18x9's all around. Would go higher on big ST tires or R comps.

I am building a 370z for str, what spring length should i go with? i am planning to maintain stock spring locations and use adjustable perches.