You are right that not everything is on that spring, but 1/4" looks a bit on the lower side. Regardless of that, more of the issue is in the front where we have much more weight and ration is close to 1:1. Even if you take out 200 lb of weight there, you still have 700 to 800 lb left. Suspension will move at least 1.5" (if not even more on street tires) during driving, so potential of binding is there. Basically, we just need to be aware of it and make sure it doesn't affect things.

 

Those numbers are pretty low already for 7" springs. 6" would probably be just over 2" of allowed travel and that is awfully close for comfort. It sucks that you can't fit 285s with them, though...

 

I measured (MS in the pics)

 

My 6" hyperco 800lb front spring has 3.5" of stroke. With the 0.91 MR, that's 3.85" of total wheel travel. Static sprung weight is about 800lbs which gives a static compression of 1.2". That leave 2.65" of travel and I set my ride height with 2" of clearance to the cut fender edge which it just occasionally rubs the edge protector. 6" in spring is just fine for length.

Rear with a 0.73 MR gives a lot more travel. Its way more than 250lbs of sprung weight though, on my 2950lb car its around 500lbs sprung weight. For a more normal 900lb/in spring (not my 1450s), that would be just over 1" of static wheel travel. Even a swift 5" spring with 2.5" of usable stroke would have way more than enough due to the motion ratio. Thats 2.5/0.73 = 3.4" of wheel travel and only 1" of static compression. Again, I use 2" of clearance to my fenders so plenty of range.

EDIT: Just quick checked my spreadsheet, should have used 0.96 front and 0.71 rear. My memory aint what it use to be

 

1"compression is 900 lbs * 2 ... are you sure?

225 lbs is per corner so ~450lbs sprung weight

 

Sorry for lack of clarity - I was only doing the (rough) math for the fronts - hadn't looked up the MR or anything and was assuming "basically 1:1" for struts.

For some perspective - the last time the car felt truly dialed in was 2013 After our daughter was born, I wasn't autoxing frequently and the only real change I made before this year was going from 600/800 to 700/900 back in.. 2015 (?) to account for the wider tires (255s at the time). So this year is almost starting from scratch for me from a combination of rust and all the rule changes.

TL;DR, I think:
* thoroughly document how the car is /right now/
* get back to a sort of known baseline alignment-wise and ride-height wise
* try higher A052 pressures
* iterate from there, trying to make one change at a time.
* worry about 285 fitment later

 

No, Im talking single corner. There is about 500lbs sprung weight per rear corner. Not sure where you're getting only 225lbs but it aint that.

 

my spring compressed ~6mm or 1/4". 1/4 of 900lbs/in is 225lbs. I think a lot factors can make a difference. I maybe 1 mm off, or my rake was not exact when jacked up from the control arms. the angle of the control arms also (my car is high).
1" is still 900lbs in your case

 

You need to double check your numbers or approach then. The back of an Evo just weighs more than that, but a lot. Factory corner weights are in the 600-700lb range and roughly 100-125lbs for unsprung weight (wheels, tires, brakes, uprights, bearings, stroked part of shock, and half of axle and control arms). The lightest stripped down drag evos would kill to get to only 225lbs of sprung rear corner weight.

 

OK. What parts make up the 1000 lbs sprung weight?

 

The back half of a 3000lb car…

 

I think I should have put the jack to lift right on the hub face somehow. that should be accurate. I doubt I'll get ~1" compression tho.

 

Do you mean unsprung weight?

 

no. 500 per corner (1k) sprung weight

 

FWIW, my car from like 2013. Wheel/tire package is heavier and I have a regular-old Autozone battery now and an FMIC so it's certainly a bit higher and frontheavier.