What spring rates are you using on a strictly drag built car with a SBC? I have 150's on now and don't feel the weight transfer like I had before with Moroso trick springs and stock frt. Springs now are at the bottom of the adjuster to get ride height back where it was with stock frt. end.

 

Here's a pic of installed spring and strut. These are 90/10 Lakewood style struts.

 

I only use coil overs on the rear. Still use trick springs on the front.

I would guess front springs are no different than rear springs. All the springs need to do is hold the vehicle at ride height however the shocks are what does all the work. Adjusting the shocks to allow them to extend or retract will depend on how heavy the spring rate is. Too heavy a spring rate and the shock barely moves. Think of road course cars that are constantly diving in and out of turns. A stiffer spring means a lot less body roll to sacrifice ride comfort. Too light a spring rate and the shock or suspension can bottom out.

I still use the SPA1 front struts. If I have them cranked to full soft, I can grab the fender of the car and bounce it up and down. To help keep the front end on the ground, I have the shocks cracked to full firm. If I grab the fender, I can't even move the body of the car because it's so stiff. On launch, this effectively slows the shocks extension rate meaning that when the front end comes up on launch, it's pulling the weight of the front suspension, tires etc quicker to add weight to keep the front end down. Once the front end is in the air, the suspension hangs down so to help out even more, I've installed travel limiters. These keep the shocks from fully extending. Now after my car has done it's wheelie off the start line, it starts picking up front weight even quicker than if the shocks were to go to full extension. Even coming down hard it's going to really rely on that spring rate. Again, too stiff of a spring rate and it's going to hit hard. A softer spring rate will be a softer landing but will also mean a lot more suspension travel.

There are a lot of different shock settings for drag racing depending on chassis setup. At the rear, you want the shocks to extend quickly at launch to allow the tires to be driven into the ground providing the squat is set right. At the front, you want the shocks to extend quickly then slowly compress as you are going down the track.

I can't remember the exact numbers at the moment but I'm pretty sure I have 110# springs on the rear (might be 90s). If I had coil overs on the front, it would be something like 140s or 160s. I did the math a long time ago. Basically, you want enough spring rate to hold the car up at ride height and not have spring bind at full shock compression.

 

Trick Springs are around 250 lb/in with about 2:1 motion ratio.

​​​150 lb/in on a strut is quite a lot stiffer with a different motion ratio and different compressed length.

If you plot the compressed spring force versus A-arm travel then you'll be able to compare how the springs are behaving..... and you might be very surprised what you see. And you can substitute for different spring specs to figure out how to tune the coilovers to behave more like the Trick Springs

 

I just found a pair of 120's local that I will be trying. I have DA coilovers on the back with ladder bars and 110 springs.