Hey i was looking around at different springs. I need to revamp my whole suspension set up. I was wondering what the spring rates mean and what type of numbers would work best for my application. I drag race recreationaly, but still use as a daily driver. i hear bilsten hd shocks work well for that but has any one heard of B&G shock or are their any others i should check out other than eiboch, and do i want constant or progressive spring rates???

i also have some real serious saggage problems in the back i believe because my drag radials are getting all cut up by trhe outer fender lip when i hit big bumps.

Thanks for the help guys,

Eli
Raptere

any more questions just post

 

You'll want more of a liner(constant) spring rate for drag racing. You want a solid control of weight transfer and axle deflection during launch.
Spring rates mean for example is if you take a 200lb coil spring, it takes 200lb# of weight or force to compress that coil 1".

So now some people are saying, "The back of our cars weight more than 200 lbs"- yes and no. The average spring rate of a factory 3rd gen spring is about 150 lbs. But that is each side. The average rear coil length is about I think 14" when stock length. When you put the springs in there and set the car weight onto them (first off, you are only setting sprung weight onto them, not the unsprung weight of the rear of car like the axle,tires, etc) the 14" long springs will sit at a stagnant ride height of more like 12.5". Thats 1.5" coil compression on each side. Both at 1" compression have a combined weight of 300lbs, at 1.5" compression *could be* more like a combined 500 lbs (or 250 lbs each side @ 1.5", and so on as the coil is compressed.

Let me explain why I said *Could be* above.

You can take two springs at 150 lbs rate, but one is 14" free height and the other is 12" free height.
The 14" free height spring will have less increasing rate force after 1" compression than the 12" spring.
What this means exactly- is when you put the 14" 150lb spring in the car may sit at 12.5" when loaded (1.5" compressed). The 12" 150lb spring will sit more like 10.75" when loaded (1.25" compressed because shorter spring will increase it rate quicker after 1" compression due to the free coils section ratio getting shorter quicker than the taller spring.

so, in conclusion-
The taller and shorter springs can both be the same rate at 1" compression (150lbs)..
But at 2" compression the taller one can be more like 325 lbs rate and the shorter one can be higher at about 400lbs rate. So taller springs will generally ride better but if they experience coil bind then they ground out and hit hard like a bumpstop if the rate is not high enough and the coils are too close together.

 

Dumb question I haven't looked into yet, how much does the coil diameter (not the size of the steel bar that makes up the spring) but the overall dim of it.

I remember reading somewhere that has something to do with the overall spring rate.

 

Hey Kat,

The smaller diameter the coil winds are the stiffer the spring will be so a smaller diameter wire needs to be used or tighter windings.

There are four things that determine the stiffness of the spring.
1) wire diameter
2) spring diameter
3) spring height
4) # of coils
example-

1/2" wire, both springs 12" tall, both with 8 coil loops or winds, just one has 2 1/2" diameter, the other has 5" diameter.
The 5" diameter spring will have alot longer length of the 1/2" wire to make up the same height and winds as the narrower diameter spring so that longer wire used will make the spring rate much lower do to leverage.

Larger diameter springs will generally give a softer better ride quality, as the same for spring height with taller giving the softer ride.

 

To better understand spring rates and how a car sits and rides, its best to realise that the sping does not normally sit at the 1" compressed state that the spring rate is taken at. Most production cars have a spring installed into them that sits much lower than the 1" compression rate they are rated at.

What this means in english?

Take our 3rdgens for example. More specifically, my V6. Now V6's factory come with about 450lb rate springs. However, those springs at installed height in a stock V6 sit at a compressed height of about 2 - 2 1/2"" range (I do not know that exact height but this is close enough for reference.) That 450#@1" spring is now sitting at about 700 lbs@ 2" compressed.
Now take my coils I have at about 825lb rate aprox. @ 1".

My car at ride height sits the coil compressed only about 7/8" at ride height. Its very stiff and the car does not hardly lower and compress the coil. My coils are much shorter than the stock ones, yet they do not compress as much because the rate is higher.

That is ride height, now lets look at suspension travel.
The stock spring is softer so it can travel about 4 inches down more than compresed ride height so about a total of 6" compressed at maximum force of a very larger dip and thenn the arm hits the bumpstop. my spring starts the car off 2" lower than stock but my total travel is only 1 1/2" max because the rate increases rapidly. So the 7/8" + 1 1/2" sits me close to 2 1/2" max compression in worse case senerio. The stock 14" tall spring at 6" compression will about equal my 12" spring at 2 1/2" compression. My rate climbs faster so on bumps my frequency recoils quicker due to the higher rate and I need higher rebound forces to counteract and damper the recoil force for a decent non bouncy ride. A stiff ride for performance, but non recoil bouncy like you see these kids going sdown the street with the nose of their cars or trucks bobbling up and down rapidly over small bumps in the road.