ok i just purchased some strange 12 way adjustable shocks with 315lb springs for the front of my car (in sig). i have a pretty good understanding on single adjust shocks but haven't found out much about the double's. i looked through some stickies but didn't find mush on adjusting shocks. can someone explain to me how double adjust shocks work and what adjustments do what? also whats a good starting point with the adjustments. and when i was looking through some post's from madman and got confused about the springs. what differance in the launch is there between a 300lb and a 315lb spring? my car weighs about 3280lb with out me in it and i weigh 175lbs. thanks

 

anything?

 

We can split the shocks and springs into two different answers, and generalize a little bit. Springs first. Springs, obviously, hold up the car as a function of their rate and compressed height. The quick answer about the difference in rates and how it affects the launch is this: Consider your launch tries to lift the front end, as it will, we hope. With a 300lb/in spring, this "launch energy" has to remove 300lbs off of the front end to get 1" of front end rise, while with the 315lb spring, it takes more (15lbs at the coil centerline) "launch energy" to get that same 1" front end rise. That's why we put a lower spring rate spring in the front. It makes the front end "sprung weight"easier for our applied energy/force to lift.
Now, the speed of any front suspension movement in either dive or lift (bump or rebound in shock terms) is controlled by the shock, too, besides its basic duty as a damper for suspension harmonics. Your shocks have a great deal of resolution for controlling these speeds. want a faster rise in the front? Crank the shocks full loose on the rebound/extension. This somewhat isolates the weight of the moving suspension components (unsprung weight) from the rest of the front end "load" that your applied energy is trying to lift. Want the car to settle down more slowly at the 60' beam? Crank the shocks tighter on the bump/compression. It's all about control. As much control as you can afford is a good idea. Always. Good luck at the track!
Bob Ette

 

thanks!

 

aeicoo - this is the 1st written explanation of the spring/shocks that I have read that actually makes sense and that I actually understand. Thanks.

David

 

Always a pleasure to share go-fast tools, we can't get enough of them.
BTW.... nice car!

 

Great answer but I have a question for your answer. Why not go to a 275/250 spring rate to use even less energy getting the car to rise? What would/could the negatives be to too low a spring rate?

 

The spring couldn't support the weight of the front end causing your front shock/strut to work harder, wearing it out and possibly damaging it and the car when they bottom out from lack of support from a weak spring.

 

Then what would the senario be to say "I need a lighter spring" Just trying to find out what the car would or would not do to warrant a spring change. Thanks.

 

keep it going guys, the more info the better!

 

Too stiff of a spring (which I think yours is in this case unless you have an iron block) will not let you take advantage of the stored energy in a lighter spring. Post 3 explains it well.

Put simply you want to run as light of a spring as possible to reap the benefits of maximum weight transfer off of the starting line, but heavy enough to support the front end to keep it from crashing back down off of the initial take off.

 

It's a good question... like many technologies, there's a point of diminishing returns. Remember that once the front suspension reaches full extension, it doesn't matter what spring is in there. The stored energy in the springs is all expended by this point. It's also true that approaching the point of diminishing returns, even your shock's lightest rebound setting will likely be the controlling/limiting factor in the speed of the front-end rise.
Down-track stability is another concern. You want your car to settle down and cut through the air well downtrack. You also want it to stay flat, and not "float" with crosswinds and track bumps. With too little spring and the resulting lower wheel rate, you're giving up stability in many aspects you want to control, and invite some dynamics you don't want. Remember those old big cars like Coupe de Villes, Electra 225s? They handled like crap due to ultra low spring rates and soft bump/rebound damping in the shocks, designed to give a pillowy ride.
Remember, too.. the more power you make, the less need for pitch rotation of the chassis. The power will load the tires, and reduce the need for "load transfer" by pitch rotation... now, if it's a ridiculously high wheelie you're wanting....
Balance.

 

Not a huge wheelstand but I would like to carry a little higher and farther out. Car comes up quick about gatorade bottle height and then immediately right back down and unloads the rear tires. I am in the middle of a lightweight front end setup and battery relocate (winter project) and plan on 120-150 lbs off the nose of the car and not sure if that is enough to try going from a 300# to a 275# spring. I plan on scaling the car ect and would hate to do it all again for a spring change if I would be at a recommended front weight to try a 275# spring.

 

Very good Info for everybody.

Your problem is a instant center/torque arm problem most likely

 

Too high or too low? Should I raise or lower the front of the tq arm mount??

 

It's typical to hit the tires too hard with your power level and a m6... lower the instant center (raise the rear of the LCA), tighten up the shocks, increase the tire pressure, put less gear in it, or REDUCE the amount of front end rise... can you launch with less RPM? One at a time is best. These are just tools, and any combination is possible.

 

Shaun,

From Madman in one of the stickies:

Hope that helps-

Zach

 

When the tq arm is in the lower position it comes up fast and then back down faster and unloads the tire. When it is in the highest position it does not get the front up at all and I lose .10 in 60'

 

Move your lcas up a hole and try the torque arm in a lower position

 

^^^Put LCA's in stock position then?? MY housing has 4 holes I am in the 2nd from the lowest with stock ride height.