Proper ride height for Track

Kingbaby

Depends on track first then spring/coil setting for the tire

So if you will bottom out adjust the coils/springs fittingly then not too stiff depending on what the tire can handle...

Stiffer and lower setups are more for road courses

Stock height/no sway bars/high spring settings/slicks are for auto x setups...helps with turn in

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03threefiftyz

No, most classes are camber limited for Z. The camber is more important than the ruined roll centers in autocross (especially on concrete). We lower the car as much as possible that doesn't run out of shock travel and/or cut the tire down. You also won't find a Z racing on this planet that does not have a front roll bar. I tested 4 different ones myself.

There are a million variables on how to set the car up for a given purpose (road race, autox, etc). Rules for the class generally trump your initial set-up goals, so you make some sacrifices along the way.

For heavily aero'd cars, by that I mean flat bottom, front air damn splitter/winglets, multi tiered rear wings, etc), the ride height is CRITICAL! The aero grip from maintaining proper ride height (something like 4-6cm) trumps mechanical grip from a softer set-up. That said, you still want the springs as soft as you can go to maintain this.

Suspension set-up is also heavily dependent on tires. If you are going to run 300mm super soft avon hillclimb tires, you are going to have to run a much different set-up than 400tw michelins.

My car is probably a full 2" lower than stock (this is with very short motons at the time). Even though the one side is loaded, you can see that the other side is off the ground, but all that much higher than what a factory ride height would be. 1000lb spring on the front/ 850lb in the rear. A little on the soft side for concrete at 2900lbs and 315 A compound hoosiers. If you tried to run this set-up on a road course as is, it would be a hell of handful.

BGTV8

These springs are close to those that the Z34 NISMO RC ships with and are what I would expect as a start for road-racing on slicks - or sticky R-spec's - with large front bar (1.25" or maybe 1.5" hollow) and a small rear bar, but only when the suspension bushes are stiffened right up.

I'm not sure why you'd consider this to be a handful on a road-race circuit unless you reckon it would be too twitchy given the stiffness in the suspension - but our circuits here in Australia are (relatively) smooth - there are a few (like Wakefield Park in NSW and Sandown in VIC) that are bumpy, but the really quick ones like Phillip Island are quite smooth and reward driver committment and a stiff chassis.

Anyway, back to the OP - beware running the car too low, suspension arms need to remain relatively flat and you need enough "bump" to avoid bottoming under braking and bumps which will make the car lock wheel(s) and dart/break-away with little warning

RB

03threefiftyz

I was referring to the set-up on my car would be a handful on a road course, it is just not set-up for high speed turns.

As far as the other poster who wrote lower CG=Good...well, yes in of itself, lower CG is good, but the Z33/Z34 roll centers start to go from meh to really meh once you get below about 1.5" from factory.

Easiest way to figure out how to spring a car is via frequency, which is easy enough to calculate using your corner weights, motion ratio and spring rate. There is a more involved means of calculating frequency, which involves chassis strength, bars, etc, but the above will suffice.

IMO, every off the shelf spring kit is going to be much to soft. They are made with a strong compromise to ride quality. That said, really good shocks will make even a 700-800lb spring entirely tolerable on the street.