Despite the rallycross being cancelled, the weekend was still educational.
These are my spring choices, they are both roughly 5" diameter by 13" free length, the shortest I can go. The spring on the left is either a MOOG spring for an Escort wagon, or a cut down Nissan Pathfinder spring. It's been so long, I don't remember. They sit kinda high. The spring on the right is what I have had in the car since I started running an open diff to save the axles: cut-down Volvo 960 Nivomat springs. With the 1/2" wider axle and the slightly lower spring perch mounting, I am getting hard tire rub on swells and dips, even when not towing the trailer. Also, the car runs hot on the highway, and turning the fans on will cool it back down even at 80mph, so I am thinking that the nose is too high and the tail is too low and it is preventing good airflow through the radiator.
If you know the wire thickness, spring OD, and number of active coils, you can calculate the spring rate. I had previously educated-guesstimated the springs on the left at 175lb-in based on how much the suspension compressed, playing with the scales at the drgastrip to get total vehicle weight and axle weight, and an educated guess on how much the rear axle/tires weighed so I could subtract the unsprung weight.
According to the calculator at edwinwhite.com, the spring on the left is 3.121kg/mm. Converting to furlongs per hogshead, that comes out to 174.76. Damn, I was off by a lot...
According to that same calculator, the cut down Nivomat spring is 2.2965 and a bunch more numbers that really shouldn't round up to 2.3 but they do. Converting to lb-in, I get 128lb-in.
So, I am going to keep a lookout for 5" diameter, 13" long 150lb-in springs. This should not be a heroic effort.
I went to change out by 175 lb-in fronts for the 225lb-in springs I have on hand, but my spring perches are seized, so I'll have to cut them off. I will probably just wait until I replace the struts with new ones.
No pictures because strut replacement is on hold for a while, since the other thing that I learned is that dropping a tablet face down on asphalt will break the screen.