ladder bar setup

Is there a way to preload ladder bars. Have an 85 tubbed with ladders and a bigblock. 1600 front and 900 rear weight. 15" slicks x32 can not launch at wideopen, have to feather it out of the hole. The bottom of the bars are parallel to the ground and chassis frame.
Any help would be appreciated.
thanks
alan

Woof! With 64 percent of the car's weight on the front axle, I'm not surprised you have to feather it out of the hole. Have you checked your pinion angle?

need more information, motor/trans/converter/tire/shocks/ struts/tirepressure...............

Yup, use differnt springs, softer with more suspension travel in front.. put more stored energy there, to lift the front and plant the rear. ALso look at putting a softer spring in the rear to allow the rear to squat or set... Then use shocks and or travel limiters to tune the weight transfere.

You cant really jack weight with a ladder bar.. You can extend or shorten the wieght pick-up point by raising or lowering the attaching point..

But what is the current pinion angle??? Bar parallel to the ground is great for transfering energy forward, but you might do better with a slight down angle... and move the weight pick-up point further forward in the car...

But you cant just mount a tab at the front and turn the things towards the ground, because your going to roll the axle down, and mess up pinion angle.. All mounting points would need to be readdressed.

Cheaper and quicker to go with a spring and shock change...

Yup, use differnt springs, softer with more suspension travel in front.. put more stored energy there, to lift the front and plant the rear. ALso look at putting a softer spring in the rear to allow the rear to squat or set... Then use shocks and or travel limiters to tune the weight transfere.

You cant really jack weight with a ladder bar.. You can extend or shorten the wieght pick-up point by raising or lowering the attaching point..

But what is the current pinion angle??? Bar parallel to the ground is great for transfering energy forward, but you might do better with a slight down angle... and move the weight pick-up point further forward in the car...

But you cant just mount a tab at the front and turn the things towards the ground, because your going to roll the axle down, and mess up pinion angle.. All mounting points would need to be readdressed.

Cheaper and quicker to go with a spring and shock change...

Kim, I simply asked if he had CHECKED the pinion angle. I did not say CHANGE it. It was simply a way of BEGINNING to analyze his problem in a rational and systematic way, eliminating potential problems along the way. Since the simple act of moving the forward end of the bar up or down CHANGES THE PINION ANGLE, that's a perfect place for problems to start. Jon was right in asking for more info......but before such info was available, you gazed into your crystal ball and told the guy to change shocks/springs without having the faintest idea what shock/spring combo was in the car. He might very well need softer ones, but wouldn't it make sense to ask the question before you talk him into parting with a pile of his hard-earned cash? You don't know what he has, but you know they need to be softer?? :roll:

I get the feeling that if I pointed to a bird and asked you, "Is that a duck?" I'd soon learn how many feathers it has, why water rolls off its back, its most likely migratory flight pattern, and a quick and easy method to track it using a homemade GPS system. :roll:

Alan.....I apologize for the hijack. I'll sign off now so you can get some great help from a bunch of smart car guys. Best of luck to you.


P.S. Tunnel rams can be great low-end torque makers. :lol:

pinion angle in negative 2 hoping this would get me around 0 under load.
I am on the lowest mount on the chassis but was thinking to weld and lower the front mount and readjust the pinion angle.
Also i want to put a much softer spring in the rear a variable 140/250 per inch spring.
The front is all tubular and tied tight to prevent front lift but i guess i need some. Have to release the front limitters for more weight transfer. I always thought with big slicks you did not need much weight transfer and use that energy to go forward not up. There is a happy medium i am sure, just have to find it.
The shocks are competition enginering shocks, unsure for what but they are in the car when purchased. Probably should go to a strange adjustable one.
Well thanks for all the help guys. Probably put this thing on the rear bumper next year with all your help.
thanks again
alan

also the spings in the rear are stiff, also what came in the car. When i push down on the rear, i can barely make the springs collapse. I think kim's original assesment is correct.
thanks anyway
alan

Yup, use differnt springs, softer with more suspension travel in front.. put more stored energy there, to lift the front and plant the rear. ALso look at putting a softer spring in the rear to allow the rear to squat or set... Then use shocks and or travel limiters to tune the weight transfere.

You cant really jack weight with a ladder bar.. You can extend or shorten the wieght pick-up point by raising or lowering the attaching point..

But what is the current pinion angle??? Bar parallel to the ground is great for transfering energy forward, but you might do better with a slight down angle... and move the weight pick-up point further forward in the car...

But you cant just mount a tab at the front and turn the things towards the ground, because your going to roll the axle down, and mess up pinion angle.. All mounting points would need to be readdressed.

Cheaper and quicker to go with a spring and shock change...

Kim, I simply asked if he had CHECKED the pinion angle. I did not say CHANGE it. It was simply a way of BEGINNING to analyze his problem in a rational and systematic way, eliminating potential problems along the way. Since the simple act of moving the forward end of the bar up or down CHANGES THE PINION ANGLE, that's a perfect place for problems to start. Jon was right in asking for more info......but before such info was available, you gazed into your crystal ball and told the guy to change shocks/springs without having the faintest idea what shock/spring combo was in the car. He might very well need softer ones, but wouldn't it make sense to ask the question before you talk him into parting with a pile of his hard-earned cash? You don't know what he has, but you know they need to be softer?? :roll:

I get the feeling that if I pointed to a bird and asked you, "Is that a duck?" I'd soon learn how many feathers it has, why water rolls off its back, its most likely migratory flight pattern, and a quick and easy method to track it using a homemade GPS system. :roll:

Alan.....I apologize for the hijack. I'll sign off now so you can get some great help from a bunch of smart car guys. Best of luck to you.


P.S. Tunnel rams can be great low-end torque makers. :lol:

Didn't notice I had a weapon pointed at the OP, nor did I offur to sell/force him to buy anything.

Pinion angle, is critical to the life of the pinion, and or drive shaft. It really has no influence on hook... unless the install is incorrect and or your using a snubber to prevent breaking the pinion/ U/joint, when the vehicle is equiped with a soft leaf spring suspension and suffers from spring wrap. Then snubber depth and impact to the pinion has to be added to the spring rate.. and changes the way the spring reacts.

Without cutting things apart and messing up what appears to be a functional pinion angle, if the tires are spinning, and it isn't already dragging the rear bumper, then the crystal ball says he should transfere more of that nose weight to the rear tires.

Outside of putting a jack on the damn road/strip, the best way I know of is to put more stored energy in the front, to help with nose lift and shift weight to the rear wheels. Or as now having continued the conversatoin and gotten added information from OP, release some of the stored energy he has captive with travel limiters.

Its a conversation....... its an opinion. Its information the OP, you, or everyone/anyone else can use or ignor as they wish.



Did I pee in your cereal one day, or is there some other reason you had to put make your second post insulting?

also the spings in the rear are stiff, also what came in the car. When i push down on the rear, i can barely make the springs collapse. I think kim's original assesment is correct.
thanks anyway
alan

If you have the front that limited on extension, I wouldn't adjust anything on the rear until you free some of the front extension. You may have everything you already need... just need to let it work.

"Soft" rear springs is poor advice, I appologise, you need a soft enough spring to allow the suspension to work, but don't really want a whole bunch of rear squat. You want to keep things so the weight pivots front to rear. First things, I would start extending the travel limiters.. until and if you have to completly disconect them. Then start with the new parts.

Thanks that is exactly what i am going to do.

Yea, if the rear suspension isn't trying to separate any at the initial hit to plant/screw the sidewalls into the track surface then it sounds like either the suspension is way too stiff (shock valving and/or spring rate), the bar angle is way too low in the front changing (calming) the leverage too much, or your "at launch" torque numbers are so low that there's not enough torque/energy to make the suspension "work" with your current shock valving & spring setup.

You asked about preloading the bars. Side to side preload is used to adjust how straight the launch is. But it is not used to adjust how hard/soft the suspension hits the slicks. Changing the spring rate to a softer spring is in a way kinda like "preloading" the suspension because the softer spring compressed further will as Kim mentioned store/release a greater amount of energy.

You might also check the suspension for any binding throughout the entire suspension travel. A suspension in a bind can appear to be sprung way too stiff when really some component is hitting something.

Also it should be mentioned again that adjusting the "pinion angle" is NOT a chassis/suspension tuning "tool" to hit the slicks harder/softer.......and should never be used as one. Setting "pinion angle", or more accurately "U-joint operating angles" (both front & rear) is set/adjusted for a car's specific intended use (street/highway use or drag strip only) to keep the driveshaft in phase under load (as in "happy"). "Tuning" the launch with the pinion angle & changing/limiting the amount of torque reaching the slicks through increasing U-joint frictional binding (by cranking in a ton of pinion angle) is a very dangerous game.

What Dave said, loose the limiters, then on to something else.

How old, what compound, and what air pressure are you running in the slicks? If the tires dont even try to bite on the initial hit, it will never lift the front anyway.

Could go old school and add 175-200# as close to the rear bumper as you can to help that rear percentage. Seen many cars go faster by adding weight.