This is for guys with ladder bar race 68 and up A body cars....

What rear coil over shocks do you use ...model # ?

what is your spring rate on your coil springs ?? and model #

Strange double adjustable with 7.0 inches of travel, 15.5 in inches extended set up with 325 lb. springs
That was on my old pump gas Duster that would hook up in a mud puddle during a rain storm

1975 Plymouth Duster
3150 lbs race ready (56% front, 44% back if memory serves me right)
Rear Shocks: QA1 DD501 shocks
Rear Springs: QA1 12HT130 springs (12" 130lbs)

Footbrake only car has typically a 1.47-1.49 60 ft, runs 10.70s.
Car as a 29.5x13.5 tire.

Cab why such a stiff spring in the back

Santhuffs double adj
12" 95lb QA1 springs
1325 rear weight

Dont get hung up on what other people have. DOnt forget that the spring makes it easier or harder for the suspension to seperate. Since every car does not have the front brackets in the same spot, one car may have a higher instant center than another car. Thus they both react different and will use/need different springs. Best is to plot out your antisquat and go from there.
Just remember, lighter springs help the suspension seperate, shocks control your seperation. Once you understand how the spring and shock control the movement, then you can adjust your car to get the best results

I think that is what they came with when I ordered them That was back in 2002 so maybe my memory isn't correct on this
That car weighed right at 3450 Lbs. with me in it with a full stock tank of pump swill, I had moved the motor back a little and moved the rear end forward a little also It was right at 50.3 % weight on the front tires and 49.7% on the rear end with me in it
I had installed 2 group 27 batteries in the right rear corner of the trunk also

I agree. Better too soft on springs than too stiff.just a WAG but you will probably land between 90 and 130 lb/inch springs.

Im just trying to see what length / model shocks are on good hooking ladder bar A bodies . I know i need around a 125 lb spring .

This car should be really consistent and its not in the 60ft. Even changed tires. It seems to work best with the rear shocks 10 cliks tight on the extension , rather than full loose . Ive moved the lower mount up and down 2 holes and either way i can press down on the trunk and bottom out the shocks in 1 inch . The preload on the coil spring is about 1/4" . With a lot more preload...it still bottoms out. This is why i think i need a longer shock ......just not enough travel . ???

Comp engineering ladder bars on mine, and Qa1 singles. Hooks and 60’s ultra consistently, but as you can see in my signature... not much power.
Stepping it up soon

Ladder bars almost always seperate . Your shock at rest should have almost all the shaft in the shock, maybe just 3/4 inch shaft showing. You want to extend the shock. A ladder bar is not going to squat or compress. what is the rear weight of the car? you can probably use a 110 or even 95lb spring. IF it likes a stiffer extension, your IC is probably high. WHich is good, its hitting the tire. Control it with the extension . You also need compression to keep it planted.
What tire pressure?
What rear weight?
What spring is currently in the car?
What is your surrent ride height at the shock (eye to eye measurement)

From what you are describing with the shocks needing to be tightened on the rebound you should want the bars in the lower holes. Should be less "hit" or antisquat.

And they should at least have some downward angle.

A light spring, compressed to hold the car at ride height, will store energy and help get the rear out and the tires applied - if you need it. I doubt you do.

A heavy spring doesn't provide that extra help. Too heavy of a spring won't compress enough to get the shocks down to ride height and/or make the thing dead stiff.

I expect a 130 spring would be fine IF you can get the shocks to the desired C-C. 110 is probably light, but usable with a good shock. I'm assuming ~1350-1400 on the rear axle.

Get the best DA shock you can afford. A cheapy, off the shelf piece may not have enough control, We've had good luck with AFCO Big Guns for controlling violent combinations without going to a custom deal.

You want to go fast. Control the housing to the minimum movement needed. Front suspension is equally important to making it work.

What tire pressure? anywhere from 10.5--12 lb , slicks


What rear weight? no idea...car is a rb dart , 3300 with driver , dana 60

What spring is currently in the car? PAC 125lb

What is your surrent ride height at the shock (eye to eye measurement) about 9 5/8"

the shaft sticking out top of shock has around 1 inch or less showing --hard to see , with car on ground , no driver

Not only do i want consistent 60' , id also like to take people for rides without bottoming out the shocks !

If this is a street car , and you want to drive with people in there , Yes the optimum shock height for racing will be too short and you probably bottom out the shocks street driving.
My suggestion:
Keep your current shocks, put 130-150 lb springs,run the adj up for some ride height, maybe 2" of shaft showing thats your "street" set up.
Get a set of decent double adjustables with 95-110 lb springs. Thats your "race" set up. You need a shock with at least 14-16" full extension. Typically you will need 2-3" extension with a ladder bar.
Or if you dont want to switch out shocks, just run the spanners up an inch or so to street drive it

Besides that, you really need to take some measurements and weight at least your front and rear weight. Then you can go on an online IC / Antisquat calculator and figure out your antisquat. It is not hard at all and you will be so much ahead of the game to know exactly where you starting.

People have made suggestions to you, but without knowing your antisquat percentage, their advice is just a guess.

Stick to the basics of how a ladder bar works
More antisquat makes a harder hit and more extension
Less antisquat softens the hit on the tire and reduces the extension.
Shock extension controls the hit (speeds it up or slows it down)
Compression keeps the tire planted
Springs store energy, so a lighter spring helps the suspension seperate. Heavier springs dont help. Typically a good race suspension will have a way lighter spring than you would expect

Those principles allow you to adjust the suspension to hit the tire harder, longer or less

I had a single ajustable shock, and when my car ran 8.50-8.30's it would literally 60 1.23-1.26 every time

If the car in your sig pic is the car you are talking about, it does look like its not seperating a lot. Get someone with an I phone to video the car from the side, you will learn more from watching these vids than anything else. Look for seperation, and what the rearend housing is doing. WHere its moving and how fast or slow.

Thanks---

definately a race car , but i like to take it out once in a while on the street .....not long drives , just a few miles and back home . Gave a buddy a ride today actually...and i could hear the shocks bottom a few times .

Ill try adjusting the spanners up like you mentioned and see if that makes a good difference

the specs on this shock say recommended ride height 10 3/4 - 11 1/4. Im at 9 5/8" . If i move the lower shock mount down 2 holes the rear of the car is wayy too low. Right now its pretty even stance

Not a very long shock. Probably can't use a 12" spring on that. I might be tempted to lower the shock mount on the housing a few inches if you can since you have the adjustment, use a standard shock like a 3850 AFCO, that you would probably run at 13-13.5" C-C with ladders, just to get the extra shock travel.

You're probably close to 1500 on the rear at that weight. I'd put 130s on it to begin with. You could wind a 110 up to get ride height, but you'll have to crank the shock up to control it.

I also run Afco big guns. I needed about 2/3 of available stiffness or more on extension for best results. 30 inch bars, 110 lb springs, 47 % rear , 3012 lb race weight 106 inch wb. 1.264, 1.266, 1.265 last three passes.

If you have to run them up that tight, you would probably drive right through a regular shock cranked all the way tight.

1440 on the rear, 110s, Big Guns cranked up, mid 1.20s. Sounds right. I'm gonna guess springs wound up some and it's not separating a ton or smashing the tire.

[
I also run Afco big guns. I needed about 2/3 of available stiffness or more on extension for best results. 30 inch bars, 110 lb springs, 47 % rear , 3012 lb race weight 106 inch wb. 1.264, 1.266, 1.265 last three passes. [/quote]

If you have to run them up that tight, you would probably drive right through a regular shock cranked all the way tight.

1440 on the rear, 110s, Big Guns cranked up, mid 1.20s. Sounds right. I'm gonna guess springs wound up some and it's not separating a ton or smashing the tire. [/quote]
10.5x33x15 about 1/4 wrinkle on the hit, some wheel speed, carries the fronts 60 feet. I have to launch at part throttle of 4200 to not overpower the tire. 2.45 low, 4.56 gear, 550 cubes.