Here's a pic of someone I know's car:

 

Say you have alot of power/your tires spin from a stop, would a stiffer spring aid to help you hook faster then a soft spring?

 

Hey that looks familiar!

 

Slowhoe you arent making me mad. I like these discussions. I'm always trying to learn more. I'm not an engineer everything I know is from trial and error.

Dammn that looks like Jays Black car!!!!!!!!!!!!!!!!!!!

 

We got some pics from the top at all? From inside the car? Is that set and go or do you have the ability to adjust it? How do you do that?

Chris

 

This is a great thread guys! Keep it up. I am learning stuff.

 

Forgive me as I have not read completely through this entire post. However have read through al least where this was posted.

This statement is inaccurate however, as I find your original thieory to be. Let's look at the numbers...

At the same stationary ride height we have;

315# spring compressed to 5” holds 3150 lbs (for ease we’ll call it 3150 lbs of energy)
275# spring compressed to 5.73” holds 3151 lbs.

Now lets start to extend the front suspension. I don’t have exact numbers so I’m going to say that the spring changes compression height at a rate equal to 60% of the wheel travel. Meaning that if the wheel moves 1” in suspension travel that the spring changes in compressed height by .6”.

So, by moving lifting the front of the car up 1” we get spring forces of;

315# spring compressed to 4.4” = 2772 # of force pushing up on the front end
275# spring compressed to 5.13” = 2821 # of force pushing up on the front end

Moving the front up another 1” for a total of 2” of front end lift we get 1.2” of spring compression change and;

315# spring compressed to 3.8” = 2394 # of force pushing up on the front end
275 # spring compressed to 4.53” = 2491 # of force pushing up on the front end

If we theoretically say that the total amount of travel available is 3.01” and look at the force supplied by the springs at 3.00” then we have;

315# spring compressed to 3.2” = 2016 # of force pushing up on the front end
275 # spring compressed to 3.93” = 2161 # of force pushing up on the front end

So, what we actually have is more force applied to lifting the front of the car as the front end lifts during launch with the softer springs and an equal starting ride height for the two springs. Lowering the ride height of the car with one or both springs will change other factors that can influence how the car launches so I’m assuming that for this discussion initial ride height remain the same for each spring. The higher rate spring actually loses it’s ability to push the front end up once the suspension is extended over the resting ride height than the lighter spring does. The extra force that is being applied by the softer spring throughout the suspensions travel during the launch is what causes the car to wheelie or carry the front end easier with softer springs.

Fact is that the softer springs loose stored energy slower than the harder springs do.

 

The inverse of that means is the harder springs impose kinetic energy faster to the chassis then...right??? if stored energy is lost slower...then kinetic energy is applied slower.

Wouldn't dumping all the available KE quickly would result in a prompt wheelstand

 

Nope. Because more lifting energy of the springs is lost before the wheels get off the ground wiht the stiffer springs. So, with less energy from the springs with the suspension near max extension the engine and rear end/tires need to have more power and grip to lift the front end. The softer springs will continue to apply more force to lift the car at larger suspension extensions.

KE is greater with the suspension exteded (not fully) and a lighter rate spring than a higher rate spring because the spring is still holding more force while the suspension moves through it's travel. Therefore the lighter rate spring will force the suspension to move more quickly while extended. The initial force applied is that of the springs while the car is at rest which is equal with both springs and holds no KE value as KE relates only to energy of masses in motion.

 

ok that all makes sense

 

hmmmm...our fun discussion came to a halt

 

Somebody sticky this SOB already! VERY useful. I now know my decision/reasoning for choosing my front springs was a bit off-key

 

So.. any of you guys think you can keep my front end down? I pull crazy wheelies and it never leaves straight when it dead hooks, I called Briggs and Stratton but they havent researched the suspension setup much????

 

Ideally for the rear shocks Brian, would something with a stiff extend rate to pull the body down on the rear on the initial hit, and then a loose extension rate, so it doesnt pop back up and unload the rear be ideal? loosen the extend rate if the track goes away.

Unless on initial hit the shock is doing the opposite of what im thinkink by comressing first then extending

 

What angle is the front shock at with the suspension preloaded a) none and b) like you were footbraking the car

 

I got a question to throw in the mix since rear spring rates and ride height was mentioned...

What's the best stance/ride height for best weight transfer? The car level, rake with rear sitting higher, or the front slightly higher than the rear? and Is there a certain front/rear ratio?

Thanks

 

Sometimes its better to think of the springs as holding up the weight rather than lifting because none the lifting of the front end comes from the front springs. The lifting force comes from the rear suspension. What doest come into play is initial compressed height of the front spring. The lower the spring rate the larger the spring compression therefore more travel required to reach full extension. The opposite hold true for a stiffer rate spring. The more the front end has to lift to reach full extension of the shock the more momentum that is built up at the time full extension is reached. This momentum or KE if you want to think of it that way along with the lifting force from the rear suspension creates the wheel stand. This is why some guys use suspension limiters on the front. It reduces the front end momentum part of the equation.

This is not to discount any of MADMAN's track testing. You can talk theory all you want, but in the end it's how it works in practice that matters.

My .02

 

bump my first question isnt all that important though, I solved the wheelstands with travels limiters. I ride on the front of the lawnmower now

 

Under what circumstances would a variable rate spring be helpful? Which would want a linear and which a variable?

Since wheelstands arent much a problem in stick cars, may linear be good for them under all circumstances and variable rate springs for auto? Just shooting thoughts out

 

I am with Granny. I would like to know if the stiffer spring up front would be better for a stickshift car as the motor does not stay in the operating range after initial launch like an automatic with a small/high stall converter.

Jay, What rate are the Strange Front springs that go with their shocks. I am running Hal's up front with an oem stle lowering spring and would like to put a different spring up front. My car will pull the tires about a foot off the ground. It only carrys them for about 4to 5 feet because its an M6. I launch at 6000 RPM and as long as track prep is there I cut High 1.5s consistantly on the current setup.

Brad