ok ive ben told i need 175lb -200lb coil springs on a sas kick, i dont under stand, if it takes 175 lbs to compress 1'' , its gona take 1750lbs to compress 10'',rite? thats what  over 2/3ds the total weight .
so for arguements sake weight is 50/50,1000lbs in front 1000lbs in back. wouldnt a 85 lb springs be rite? lets say i have a springs 18'' long and will compress to 12'' 12/1000=83.333
so wouldnt that be rite ?
1000 in front 1000 in back

What about the weight when you are jumping
or cornering, I'll tell you 175 Lb springs are really
soft, I bet 200 or 225s are too, but better than
the 175s

Good Luck
Wild

F=MA ... or Force = Mass times Acceleration

So under normal gravity (aka 1"G"), you're correct (this is the "acceleration component"). An 85lb spring will"support" the mass under 1G. But, as you corner or hit bumps, the "G" factor can double or triple (or more), that means the force will double or triple (or more).

One more thing to consider ...  many springs are progressive, so they aren't necessarily a constant rate (might be 175lbs for the first inch, but 180 for the next, etc).