Eric my question is in regards to knowing when to try lower rate springs. We have a 3150lb bracket car that makes about 550HP. It has a ladder bar rears suspension with single adjustable coil over shocks and we are currently using a 150rate spring as that is what the chart suggested based on rear end weight. The car leaves pretty good and has averaged low 1.40 60fts. I believe it should be about 5 hundredths or so faster on average but its something that we are trying to get better with while not moving too fast. I've wondered though if our car would benefit from a softer spring in the rear. I've personally called two well known chassis builders and have received two very different thoughts on what spring to use. One said to stay with the 150 and they other said to use a 95 rate spring. I've seen both of there cars run and they both leave good and are fast(one def leaves better though). So with all that said, What are your thoughts on the matter?