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Need a little advice and or experience !

The class I run in made a rule change this spring. I just getting my new engine together and want to take full advantage of this rule change.

Instead of a short anti-axle wrap device we are allowed to run a bar (ladder bar) any length in any direction from the axle, one per wheel.

Here is my plan:
I want to attach the bar about 3" below the rear axle tube center line with a good strength mount and attach it to about where the front U-Joint on the rear driveshaft comes out of the transfer case to the frame. I think that the ladder bar has to be somewhat parallel with the ground so the frame mounts will have to have a few holes for adjustment. I will use some sort of heavy duty Hiem joint so as to not bind the suspension.

I guess the question is how long do I make the ladder bar to allow weight transfer to rear and some lift on the front ? Do I need to get the truck to a scale and find the instant center and such or can I get a close with a guestimate from you guys to make this work or get a measurement from one of you. I am using Rancho 9000 shocks on rear now and the AFCO 90-10's on the front. The rear springs have been cut short behind the rear axle to allow some squat. Is this enough info for now ?

The truck is a 79 F-150 4x4 short box, strictly mudrace fast track type pits.

Thanks Mark
 

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My ladder bars are just shy of being 6ft long, 3/4 heims front and rear, 1" DOM seamless tubing with .250 wall. Extended front radius arm mounts and mounted the front to them. I have a 107in. wheel-base.
 

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mine are 4 ft long, schedule 80 pipe, the mounts could be a little stronger but, ill wait til the bend to fix them i was in a hurry!! so far i love them
 

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Mine are similar to Critters, but are 5' long and made of chromoly. for the rear mount, I picked up a bracket set from S&W racecars and for the front, I use their driveshaft loop crossmember with the adjustable drop mount. Here's a bad cell phone pic of the bars mounted to the axle:

 

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to keep me in class rules of needing to have a leaf sprung rear. Look a little closer and you'll see those fancy coilovers that are really doing the suspension work. The monoleaf on spring sliders really just centers the axle under the truck.
 

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Mark, There are WAY too many variables to go into in just a few sentences in a forum like this. I'd suggest that you purchase the book " Door Slammers: The Chassis Book" by Dave Morgan......It's ALL in there. ;) I bought it before I started building chassis and I've never looked back......And yes, In part it has to do with instant center and yes, you'll have to accurately scale the car......
Rob
 

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Mark - my old ladder bars were roughly 3 feet long, they seemed to make the rear lift slightly. I removed them and ran seperate top and bottom arms, bottom being quite long, about 6 feet, top not sure on length but its roughly 3 feet I think. The truck squats slightly now on take off. I will try to fine tune it maybe this winter after doing some more research though, I think there is more I can do to get the front end up still.
 

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Mark, There are WAY too many variables to go into in just a few sentences in a forum like this. I'd suggest that you purchase the book " Door Slammers: The Chassis Book" by Dave Morgan......It's ALL in there. ;) I bought it before I started building chassis and I've never looked back......And yes, In part it has to do with instant center and yes, you'll have to accurately scale the car......
Rob

The Chassis Book" by Dave Morgan...... is 80.00, is this the going price? :eek:
 

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Discussion Starter #10
Thanks for all the replys and pics guys !

It looks as though I will have to put a little more thought into it. I may just fab up a system for the last half of the year and then later this fall & winter rework it to get the most out of it. I will have do to some reading and measuring LOL.

Thanks Again Mark
 

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I don't go in the mud. but if i did i would keep the bars as close to the bottom of the axle as possible and as close to the frame as possible. I have a long bed truck and mine are about 6 feet if im remembering right. It doesn't have any wheel hop and i have loaded the suspension down about 6 inches and my bars were still loose. I followed the rule keep the bars the same angle as your driveshaft. im not sure how much they lift on the truck but they don't bind up and i have no axle wrap. I have seen many different types of bars work though. And i can't say whats the best but mine work for my application.
 
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