69_YENKO

iTrader: (16)

Hopefully this will make sense.

I bought a set of AFCO coil overs off a friend and sent them in directly to AFCO for a rebuild before using them. my buddy told me that he thought they had 250# springs on them but wasn't 100% certain. I asked AFCO to check the springs out and let me know what I had and also asked if they would help spec me out the right spring for my car.

the Tech asks me what the front end weight is, so without having scales and the car being on jackstands I went off the numbers posted by MADMAN in the sticky. It lists about an 1890# front end weight for your normal 3,500# car. I've got the front swaybar, bumper support removed and some Bogarts on. so i figure maybe a tad bit lighter. if its not yet, I plan on shedding some more fat later so it should be.

I tell the guy the front end should be about 1850# and he tells me for my car, for a drag setup, at 1850# I need a 450# (may have said 415, but still?) spring. I asked him if he was sure, that most people run them in the 275-325 range depending on the application to which he replies, not at 1850#s they dont.

Whats the deal? all i could think of was maybe he was specifying a shorter spring then is normally used, which would need more rate to hold ride height?
anyone care to comment on what I should go with?

MADMAN

iTrader: (4)

Call me at the shop. I can get you situated

ty_ty13

iTrader: (42)

curious as to what brian says...

MADMAN

iTrader: (4)

You need to explain which front suspension you have. Spring rate is dependent on where the shock is mount to the lower control arm and the upper mount.

ty_ty13

iTrader: (42)

on the 25.3 car you're putting together (white v6 car) with the 2" drop spindle on it.

when you have the car at ride height does the suspension feel (sapose to feel) kinda bound up? mine moves but it definately feels really tight even with the shocks loose.
i have the 325lbs 14" springs you reccomended on it and the spanner is really, really close to the top of the shock body to get the right tire and fender clearance it needs. i do have the front wheels tucked inside the fender also..

i'll call if you'd rather me do that... which ever way...

Tyler

SPEEDYws6

iTrader: (9)

Sorry to hijack, I'm kind of confused also.

What has more stored energy? A 300lbs spring with the spanner at the bottom if the shock, or a 250lbs spring with the spanner high up on the shock. Both at the same ride height.

DMH Fabrication

iTrader: (126)

The energy stored in the spring is equal to 0.5*k*x^2 where k is the spring rate and x is the distance the spring is compressed from the static position.

Lonnies Performance

iTrader: (16)

Typically both will have the same stored energy, but the lighter spring will offer more weight transfer, unless the shock length limits the amount of extension.

A spring with twice the stiffness only compresses half as much under the same weight.

69_YENKO

iTrader: (16)

Talked to Brian earlier and big thanks to him for getting me taken care of, he even called AFCO to check on the info they gave me.

Apparently there was a mix up when I called AFCO and the guy thought I was talking about a first gen F-body which has different suspension geometry with the spring mounted more inboard thus needing a stiffer spring rate.

Thanks Again MADMAN!

DMH Fabrication

iTrader: (126)

Your example does not have the same stored energy.

1. First spring with rate k and compressed x distance:
KE=0.5*k*x^2

2.Second spring with rate 2k and compressed 0.5*x distance:
KE=0.5*2k*(0.5x)^2 = 0.25*k*x^2

They do not have the same stored energy.

MADMAN

iTrader: (4)

The suspension is free moving on all the cars we set up with the drop spindles. We try to put them all the cars we set up.

SPEEDYws6

iTrader: (9)

Well I guess I would just have to compare the two on the car to find the compressed lengths. That sucks.

sr71bbjr

iTrader: (52)

Hey brian,

Is the 325 spring good for my car with a lsx block and a turbo hanging off the front? I to have the racecraft 1in shorter control arms so i think i might need a little more spring?Everything you put on the 25.3 car i have on mine. This is for my 25.2 car that you put all the fiber glass and carbon on.

as always , thanks in advanced.

Bryan Pomeroy

mad_steve

iTrader: (2)

a 325lb spring should be the right rate for your car.

01FbTaWs6

iTrader: (12)

dont mean to bring this back up, but willa 300lb spring work fine on the front of a full weight trans am? Im picking up a set of 12 way adjustable QA1's for dirt, and they have 300lb springs on them. I do drive the car on the street.

69_YENKO

iTrader: (16)

300# spring should work fine for you, back when I had my QA1s thats what i used and now again with the AFCOs, the way I understand it a 325# spring would be more for a car with an iron block, and a 275 should be for extensive weight reduction A/C, PS, bumper supports, k-member, etc...

01FbTaWs6

iTrader: (12)

awesome! thanks much