Front coil over guys. Need some advise

Ok, so I have made changes to my car. And it doesnt work anymore.

Im wondering what weight spring you guys run in the front of your car. I would like to hear from race car guys at or under 3100lbs

Are you talking about coil overs on stock or an aftermarket rack and pinion set up? The rack and pinion set ups seem to get away with lighter springs due to shock angles and the mounting points of the arms. Coil over conversions on stock stuff would be around a 450lb spring.

Still no hook? How much travel do you have now with the coil overs? Calvert likes to see 5" of travel and that seems like it could be difficult with a coil over in the stock shock location.

Shouldn't be, I was building coil over kits for awhile and my kits had dead on 5" of travel at the spindle.

Depending on the front weight... 350 would be close
or 400... put it on a scale
The length also matters

Most of the coil over and strut front end drag cars with four links or ladder bars cars I've heard of have three inches front travel

Im at 4.75" of drop now. I only had like 3.5 before when the car was working.

I have a 300lb spring in it now and really dont have it compressed at all

Then put a 250 or 275 on it...the front must be light
but you will have to control the lift with good shocks
EDIT
more than likely your looking at a 6" spring in the
250-275 range... that will give you stored energy
and wont let it fall out... but again you will have to
slow it up on extension so you dont get full travel...
if it dont need the travel... but I would rather have to
much than to little

Seldom is it how MUCH travel, it's usually RATE of travel. This is a moderate HP car, so while it won't need much travel, it will need some stored energy to get things started. So the issue is likely a combination of shock settings and the fact that the car is just sitting on the springs

Monte, thats exactly what Im thinking . I really dont know how to compare a /6 torsion bar to a coil spring

If you push up and down on the front of the car does the front of the car move up and down or is it stiff?

A torsion bar is a spring, so it has a spring rate............where to find that rate, I don't know. It also depends on how you mounted the shock. The more straight up, the less spring it needs

I guess the way the top mount piece comes out on the angle makes the shock more verticle. The front is very stiff, not like it was with the torsion bars. However, stiffer rebound setting on front shock was helping so I wasnt sure it needed to be loser

You said the shock compresses very little.. you
need lighter springs to get the shock down in farther
but stiffer shock setting... you had 3" before when you
lifted it up.. but now with the 300# your not working
thats because you dont have the 3" anymore.. you have a
lot of non stored energy... get the shock(rod) in farther
but be prepared to stiffen the shock rate to slow it down

Shock is compressed. Coil is not. I just ordered #250s.

This is a coil over shock correct... how do you
get the shock compressed and not the coil.. unless
the spring is way too short.. if thats the case like
I said a 6" at 250

my spring rate is 300 0r 350 and i have 3.75 inch of upword travel

When you compress the coil on a coilover shock then the shock extends and vice versa

When I let my car down on the suspension the coil overs and spring compress, not extend They extend when I jack the car up and let the suspension hang down on of the coil overs, front or rear

Seems to me that you can find the torsion bar rates in an old circle track chassis book. I have an old drag chassis book and I will look and see if it's in there.

I know I have seen the rates published.

not what I'm saying. With the car on its weight, the front shock is nearly fully compressed now that I lowered it a little but the spring isnt compressed now because I turned those spring nuts down. get it?

I would be interested to know if you can find that

a page from AndyF

http://arengineering.com/tech/torsion-bar-tango/

Here is what I found. You do need to read the AR tech page because the numbers do not translate exactly. But from the looks of it, even a 250# spring may be a bit much for you.

.810 90/lbs-inch P5249148 Drag race
.830 100/lbs-inch OE /6
.870 120 P5249149 Resto 340
.890 130 P5249150 Resto 383
.920 150 P5249151 HD V8 handling solo
.990 200 P5249152 Solo and RR
1.040 250 P5249153 HD solo and RR
1.090 300 P5249154 CT 1/4 and 1/2
1.140 350 P5249155 CT 1/4 and 1/2

As long as you understand the wheel rate thing Andy has posted you can figure out what you had, and what you need to get close.

Turned the "spring nuts" closer to the shock mounting eye? It sounds like you took all of the preload out of it to lower the ride height. The correct springs should have some preload at the desired ride height. Sound like you need a lighter spring. Also, if the shock is near full compression at the desired ride height, it sounds like they may be a little long, especially since you drive on public roads.

I read the text and a chart was mentioned but I never did find a chart.

Yes. Well 250s are on there way. It doesnt appear you can use a torsion bar spring rate as a comparable to a coil

You can. I'm pretty sure that Andy at AF engineering can figure it out. I'd bet those 250's are gonna be on the heavy side.

Nope, because while all springs are rated in inches............where they are mounted makes a huge difference. Same as the rear. If the rears are straight up, 110s may be all you need. The shocks are seriously angled, you may need 150s. On the fronts, how close to spindle and angle make a difference. All about leverage

It would appear that i am collecting coil springs. This will be the 3rd different spring on the front in 7 months

When you compress the coil on a coilover shock then the shock extends and vice versa [/quote] When I let my car down on the suspension the coil overs and spring compress, not extend They extend when I jack the car up and let the suspension hang down on of the coil overs, front or rear [/quote]

not what I'm saying. With the car on its weight, the front shock is nearly fully compressed now that I lowered it a little but the spring isnt compressed now because I turned those spring nuts down. get it? [/quote]I do now

Monte, can't you calculate the numbers if you know the wheel rates for both the Tbars and coil overs?

Not to totally bury you with information, but to minimize your spring collection read through this thread: Pirate4x4.com Spring Tech

There is a mountain of info in there that is offraod based, but I'm sure some of the theories and math applies to coil-overs independent of the application.

You should be able to use the current springs or the 250's and back calculate your corner weights. I've read that whole thread and the general idea is to use the lightest spring possible to support the rig with a certain amount of preload and let the shocks control stuff. I see no reason why that isnt a pretty good idea on the track as well. Offroad uses much longer travel shock, but something like 3/4-1in of preload should be a solid starting point on a 5in travel shock.

Edit: Also, working from the springs you have now should give a better idea of what rate you need than all this torsion bar / wheel rate stuff.
Disclaimer: My car has torsion bars and has made 14 passes in 4 years

Torsion bars and coil overs can be compared by using the wheel rate. Just takes a little bit of math. The coil spring is going to act about half way out on the lower control arm while the torsion bar works on the end of the lower control arm. Once you adjust for that difference you can compare them directly.

The slant six bar has a wheel rate of roughly 100 lbs/inch. If a coil spring is acting half way out on the lower control arm then you would want a 200 lb-inch coil spring to match the wheel rate of a slant six bar. I know it is roughly 1/2 way out but a person should really measure where the coil spring is acting in order to figure out the wheel rate.

Ok, well all this makes me feel better. I have not heard of a car as heavy as mine using anything below 300. So if the 250 still seem like there to much, ill go even lower. Thanks guys

I think your springs are too short.
You shouldn't use the spring platform nuts to adjust ride height. You will end up with no preload (what you have now)
Or too much preload. Witch can do strange things when you hit the brakes on the top end.
Don

Good thread ray, I ditched the /6 bars also and went coil overs, wasn't sure on Spring got a 300 I'm thinking it was 12" afco doubles I am gonna try. I'll prolly need your help on this eventually

Mr p body happy birthday

What length springs are you buys
EDIT
With the bottom adjuster set at 1" up from the bottom
your shaft should be where you want it... if its just
a little off move it with the adjuster... more than 1"
the spring is wrong

Not necessarily MrP. I understand what you are trying to say, that in MOST instances you want the spring platform to be in a certain range and if it is not there at ride height, you have wrong spring..............BUT, many times I tune "reaction" with a spring. I have purposely done what Ray has, with too heavy a front spring because I DON'T want any stored energy in the spring. And vice versa. I have purposely run a way light spring and cranked the platforms way up to get the reaction I want. So there are several ways to do it based on what you are trying to do. I have also run heavier springs than needed on the rear for various reasons. As with anything else, it's a tuning aid

When I jack up my car the front suspension is limited in extension by a travel stop built into the UCA, that is nothing but a bolt that has washers to determine how long it is. The front shock body is not used as a stop on either end of travel. And OBTW, I think my 8" long springs on the Viking shocks are 450# to hold up the Mega block engine in it now.

I have 275's in mine.

I Have 275lb 10in springs on 3850 Affcos mounted almost straight up and down on a Bobs Pro Fab front end, Bondo Bob recomends 250lb springs on A-body cars, i somehow got shipped 275lb springs BUT i had to move my lower coilover mount on my lower control arm inward some so the extra 25lb compenstaes for the inward movement of the mounting point. this is on a all aluminum motor, stock location. if i ever install the aluminum headed 440 then a 350or 400lb spring would be my choice. btw call Bob @ Bobs Pro Fab he full of knowledge on this stuff.

You made me buy 350s. My life would be cheaper without you in it

Torsion bar rates are at the wheel not with a 250 lb weight sitting on top of a coil spring etc. to measure lb/in. An example is it takes like a 600 lb coil to get a 350 lb "Wheel rate". Don't freak but Firm Feel has Wheel rates on their website for torsion bars.

But it is so fun spending your money!!

10-300 spring on the front of mine.....