? about spring rates

[firebob]

I'm working with my 69 firebird and I'm looking at getting new leaf springs. The original HD 4 leafs springs are reported to have been 126lb spring rate. I was looking at another pair that were 140lb linear rate.
My question is would the higher rate be better or should I stay with the original rate? My bird is dropped about 2 inches from stock front and back.

Robert

[MonzaRacer]

OK a higher rate means it takes MORE force to deflect, ie bend them straighter hence a flatter cornering car. if you want a cushy ride, no dont change, if you want to turn a corner and keep it off door handle than you go for stiffer springs, bigger sway pars and multiadjustable shocks.
Now if you want better handling and better ride then go look at ridetech.com and the rear 4 link with doble or triple adjustable shocks or possibly shockwaves instead of coil overs.
See specific springs have rate spec of say compressing one inch or what ever the spec is for every 140 some odd lbs applied.
Now a progressive rate spring is more liberal and will over tax you,, oh wait thats a liberal politician, I mean a progressive rate spring is one that the spring rate changes as the load stacks up, ever see a new coil spring with two or three coils real close together? Moog used these so as soon as those close coils touch the spring rate changes.
Just like cutting a 15 in long 180lb spring by 1/2 coil may make it 185lb or 200 lb spring rate. Rates are based on diameter of spring material, the twist or bend(arch in leafs), heat treat closeness of coils or leafs to each other or number of coils or leafs also.
Ever see a truck with bottom leaf being flat and real thick, when the main leaf touches it the effective RATE gos up as the part that touches that bottom leaf that normally doesnt touch but when it does the main spring pack cant bend past, hence it makes the complete spring ACT heavier and lend a truck or car ability to ride softer till load compresses springs.
Honestly leaf springs were on Conestoga wagons, old tech. The new bolt in 4 link set ups from Ridetech with either spring set up coil or air are so much better handling , and properly installed you can get lower looks with similar spring rates. air ride allows from seat tuning, at least of the spring rate. And a pound or two of pressure can make car faster or slower. One click on adjustment of shocks can make difference of car pushing or sliding the front wheels through a turn or having a car with a loose rear end, ie rear end slides.
Basically if you LIKE what you have and are not gonna autocross or road race or anything,,,leave it. Otherwise educate your self on springs. one book is How t o Make Your Car Handle by Fred Puhn, amazon can sell you one most likely. it also explains how suspensions work and even gives you means to figure the math out, unless you just wanna drive it around like a grandma.
Good Luck

[firebob]

Thanks for the post Lee. Well I don't drive like nobodies Grandma(maybe Grandpa :))!!LOL
This is a double post because one got moved so I'll close this one and use the other thread.