Helper Spring Size and Stiffness
 

I'm looking to buy some helper springs for my coilovers to help restore the stock amount of droop while maintaining the ride height. I did some quick calculations (that could very well be incorrect) but I came up with the result of if I use Swift 1.5kg Helpers with my 8k/9k setup that I would get an initial spring rate of approximately 71lbs front and 72lbs rear until the helpers fully compress at which point I would have the standard 8k/9k rates. I want the helper to be compressed completely while on the ground but have enough rate to allow the suspension to droop sufficiently when driving over dips in the road. Does this sound right?

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Why don't you just get new springs?

I could get longer springs for the front but the rear coils are almost maxed out so a longer spring may raise it up too high. The main thing I'm looking to do is add some more downward travel to the suspension. Helpers would help me to that and maintain the ride height. I want to have a helper that is stiff enough to rebound the suspension adequately over road imperfections but soft enough that it's fully compressed all other times as I don't want a dual spring rate. Just trying to weigh my options at the moment.

You can figure it out with math. You can find the corner weights, then find the compression distance of the springs. Spring rate*distance=force. That is your max rate to fully compress at rest.

Swift helpers are 60-70mm in length so a 1.5 spring should be fully compressed but I'd like to go 3 as ultimately I want to go 6k/7k springs with the helpers installed. Maybe I'll swap the main springs first as it's not much more expensive to get those and see if that gets the results I'm looking for. Just looking to see if anyone else has done anything similar. I would absolutely go YYZs and Konis if the ride height was lower in the back. My previous setup was Road Magnet springs and 08+ FE5s but I didn't like the rake.