ladder bar - coil over setup

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ladder bar - coil over setup

Post  hpwdboss1 on October 17th 2014, 5:49 pm

I'm a tractor puller but I've gotten involved helping a buddy with a drag car. It is a 78 fairmount wagon w/ 9" and ladder/ coil overs. We had to dismantle it 100% due to age,  rust, and gumball welds. It's time to put it back together now. I need to find information on proper initial setups on rear. Are there books, manuals, or something I can use to help with the learning curve? Maybe good DVD's? It's all new to me, but I ain't skeerd! Very Happy


Last edited by hpwdboss1 on October 17th 2014, 5:50 pm; edited 1 time in total (Reason for editing : my stupidity)
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Re: ladder bar - coil over setup

Post  68formalGT on October 17th 2014, 10:40 pm

Door slammers by Dave Moran.
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Re: ladder bar - coil over setup

Post  maverick on October 18th 2014, 9:23 pm

I want a Fairmont wagon.
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Re: ladder bar - coil over setup

Post  DILLIGASDAVE on October 19th 2014, 10:34 am

Assuming a number of things.......

(A) That this is a drag only car (no street/highway use).

(B) That the front suspension (regardless of type) has the same spring rate both sides. And that both front springs are sitting/adjusted to the same spring height (no side-to-side spring height stagger).

(C) That while the car is sitting at race ready ride height the crankshaft/trans tailshaft C/L is pointing directly at the pinion C/L & the pinion C/L is pointing directly at the crank/tailshaft C/L.

(D) That the rear coilovers have the correct rear spring rate choice that will allow the coilovers sit at the shock makers suggested center-to-center installed height while the car is sitting on the ground at compressed ride height & fully loaded race ready weight including driver weight. And that the rear shocks have the same spring rate & installed height adjustment each side (no spring weight or height stagger side-to-side).

(E) That it doesn't have wheelie bars.


If the above applies to this car then this is my long winded example of how I do a basic initial setup on a ladder bar car......

(1) Square the rear housing under the car. If you are 100% sure that the ladder bar X-member/front ladder bar brackets are installed 100% perfectly square in the car in relation to the car's nose-to-tail centerline then you can usually use it as a measuring point to square the rear housing. If you're not 100% sure about the Xmember you will have to square the rear housing off the car's nose-to-tail centerline. You can find the car's nose/tail centerline (or close to it) by marking the centerpoint on a number of chassis crossmembers front-to-back. Then drop a plumbob to the shop floor off of each centerpoint & stretch a string on the floor to represent the nose/tail centerline. Then square the housing off the centerline string.

(2) Choose a front ladder bar hole. If you have no real idea how much power/torque the car might actually have to work with then (as a starting point) just choose whatever front hole that will allow the bottom bar to be level with the ground (or slightly downhill) while the car is sitting at race ready ride height. At this point you can leave all the ladder bar jam-nuts & mounting bolts hand tight/snug, just don't fully tighten anything yet.

(3) With the housing square in the car/chassis & having chosen a front ladder bar bracket hole, the car's front & rear suspension needs to be compressed to the race ready ride height at full race weight including the driver's weight. So to do this correctly & still have enough room to get under the car to adjust the ladder bars you either have to (A) place the car on the ground, and be a super skinny bastard to get under the car, or (B) use a drive-on car lift to mimic the car sitting on the ground at ride height & have tons of room to work under it, or (C) place the car on "set-up" stands (or cinder blocks ..... if you're brave enough to risk it) to mimic the car sitting on the ground at ride height & have a limited amount of room to work under it.

(4) With the car sitting compressing the suspension to race ride height at full race weight spin both ladder bar adjusters to set pinion angle (aka rear U-joint operating angle). If as mentioned above the car's pinion C/L & crank-trans C/L were both already initially pointing directly at each other (giving you 0.00* degrees U-joint operating angle at both front/rear U-joints with car at ride height), then all you have to do is adjust in a little negative pinion angle (in relation to the driveshaft C/L, not the ground) to offset any possible positive pinion rotation/change that might happen during the launch. By design ladder bars can create more pinion angle change under load than 4-links usually do. But that doesn't mean that ladder bars need a ton of negative pinion-to-driveshaft operating angle to keep the U-joints happy (like people use to think in the old days). Aftermarket drag 4-links can sometimes use as little as -.75* pinion angle, but the adjustment range usually is set somewhere in the -1.00* to -1.25* (and sometimes -1.50*) range. A normal drag only ladder bar car usually needs a little more, but not much more. If you take the time to map-out the L/B suspension travel vs pinion change you might be able to use as little as  -1.00* pinion angle. But the normal drag L/B adjustment range is usually somewhere in the -1.25 to -2.00* pinion angle range.

(4a) If the car doesn't have the above mentioned desired "drag - only" driveline angles (or close to them) as a starting point to work with, you can sometimes fudge the angles a little, but not too much. An example of "too much" would be if the car was built with something really way off, like a super wonky slip yoke to driveshaft U-joint operating angle. In that example there might be no amount of fudging the pinion angle to make up for the fuuked slip yoke angle to avoid vibration & U-joint binding. If that was the case the driveline angles would have to be corrected before moving on.

(5) After the pinion angle is adjusted, lock it in by tightening any/all loose ladder bar jam-nuts on the driver side bar. Also make sure the 1 front & 2  back ladder bar mounting bolts are tight on the driver side bar at this point.

(6) After the driver side ladder bar jam-nuts & bolts are all locked down & tight, you then adjust the passenger side ladder bar adjuster so that you can easily spin/remove/slide it's front rod-end bolt in & out. At this point the car has in effect "zero preload" on the passenger side ladder bar. This can sometimes be a real good starting point choice for the side-to-side preload setting on ladder bar cars & make them launch straight depending on how much power/torque they have to work with. But this "zero" setting might also cause a car with lower power/torque numbers to launch to the right. If the car launches to the right add preload to the passenger ladder bar adjuster, if it launches to the left remove preload from the passenger ladder bar adjuster.

(6a) If you suspect the car might not have a ton of "launch torque" to work with, it might be a better idea to not use the zero preload setting on the passenger side (as a starting point) in favor of adding a small amount of preload to the passenger side ladder bar's "zero" setting. Just adjust in enough passenger L/B adjuster wrench flats/preload to the "zero" setting to in effect raise the passenger ladder bar front rod-end a little with the bolt removed (something like a half a hole up from "zero" is common). Then pull the rod-end back down & install the front rod-end bolt & lock down all the passenger side jam-nuts & mounting bolts.

(7) Adjust the housing centering devise (diagonal link, wishbone, or whatever is used) to center the housing/equal the slick's sidewall-to-frame spacing.

[8] Adjust the rear coilover shock valving. If they are single adjustable shocks (extension valving only), & it's a low to medium powered car, initially set the ext valving adjuster to somewhere around the 50% to 70% tight range. So a shock with a 10 click window would initially be set at 5 to 7 clicks from full loose (or 5 to 3 clicks from full tight). A car with decent to big power might need them set tighter initially, say anywhere from 60% to 90% tight.
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Re: ladder bar - coil over setup

Post  hpwdboss1 on October 19th 2014, 5:00 pm

Thanks Guys.
I'm going to start with the initial locating and grab a copy of D. Morgans book and try to get more educated at Busted Knuckel U. Cool
Thanks!!
Perry
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