The lower portion of the bar the long side should rest parallel to the ground at ride height. We also measured and marked the wheel center to front ladder bar mounting point at ride height. You must measure carefully several times to get the crossmember installed properly. Using the measurements taken earlier, we set this position on the passenger side, measured to common points driver and passenger both in front and behind that crossmember center point, and transposed those measurements to the driver side.
This ensures the crossmember runs perpendicular to the subframe connector rails. The front ladder bar brackets were used to mark the subframe. With the bracket rotated so that the pick-up points run degrees to the ground straight up and down , and the upper edge just touching the floor, the connector was marked. Note the roll cage tube coming through the floor- this will be tied to the crossmember tube for extra stiffness.
The rails were trimmed out with a plasma torch. Cutting half-moons with a hole saw is tough on the car. The cuts were dressed with a grinder. We used a special adjustable rear-end to set the height of the car. We measured both the vertical wheel centerline and the ride height.
More on the adjustable rear in a future article. This unique device allowed us to mount the wheels and set the width of the rear end so we could narrow our 9-inch housing. Once the rear end had been built, the rear work could begin. The ladder bar crossmember was held in the car with jack stands and the position of the mounts were set. We measured 2 inches from the inner side of the subframe connectors to the outer mount.
The ladder bar rod ends were bolted in place to keep everything lined up. The mounts were tacked in place under the car. Only one side, the other side must match, and that comes later. The entire crossmember was removed and the brackets were fully welded.
The outside and inside edges of the brackets should be welded up. Next, the mounts for the other bar were assembled in the same manner and the entire assembly placed on the floor. The fully welded side ensures the correct geometry for the unwelded side. We measured each side to ensure the opposite mounts were in the right place.
Nice and simple. Then the crossmember was reset into the car and welded in place. The rod ends were reinstalled into the bars with anti-sieze and bolted in place.
We set the ride height to the center position, so we had some adjustment room. Then the rear end mounts were installed and placed up to the rear housing. The optimum position for the rear end is degrees down angle to the front of the car. This provides the right geometry for the driveshaft rotation. A magnetic angle protractor is really helpful for this project. The ladder bar mounts were tack welded in place only tack welds at this point , as well as the shock mounts.
You can put the shock mounts anywhere, but the further apart, the better. We kept it simple and placed them between the ladder bar mounts. The shocks no springs yet were assembled and bolted to the lower mount. The upper mount ears were positioned vertically and the placement was marked for the crossmember.
We used a PipeMaster notching helper to get the right shape for the notches. The crossmember was then installed between the rear down bars. Before welding, the bar was squared to the body. Each side was measured to the inner edge of the trunk lip. Once set, the bar was welded in place. We slid one of our Miller welding sleeves over the shock to protect it they are nice looking!
It is always best to set the shocks as close to vertical as possible. Assembling the shocks was a little tricky. We had to use a set of spring compressors to get the upper retainer in place, even with the lower retainer threaded all the way down.
The shocks were bolted to the lower shock mount using the supplied hardware and spacers. The ride height can be adjusted using the threaded lower retainer on the shock. We have not gotten that far yet. The finished mock-up install. All that is left is to pull the rear end and finish welding the brackets in place. The last step is mounting the track locator bar. This bar centers the rear housing under the car.
The track locator bolts to opposing sides one front and one rear for the ladder bar mounting bolts with rod ends. Turning the rod moves the rear left or right depending on your needs. Notify me of follow-up comments by email. There are many different versions of these types of traction bars for leaf springs. A gap is left between the snubber on the front end of the traction bar and the spring. The gap can be different on either side before slapping the frame or the front of the spring depending upon the style in use , thus creating preload.
Moving the driver-side traction bar snubber closer to the frame creates preload, helping to keep the car from turning right. If you need more preload, adjust either the passenger-side snubber first choice closer to the frame or back the driver-side snubber second choice away from the frame.
If your car turns right upon launch, you need more preload and should adjust the passenger-side snubber closer to the frame. If your car turns left upon launch, then you need less preload and should adjust the passenger-side snubber farther away from the frame. Remember, the more distance the snubber is from the frame or spring the longer it takes before the car reacts to your settings.
For those of you running rear-wheel-drive GM cars with leaf springs, Landrum Spring Company makes what they refer to as a Parabolic leaf spring.
The Parabolic spring is a mono-leaf design that is thicker in the middle and tapers as it moves closer to the ends of the spring. This thinner leaf at the end allows the car to plant the rear tires quicker and harder. The thicker middle part of the spring helps prevent spring wrap-up. You still need some sort of slapper bar or a set of CalTracs traction bars to stiffen up the front half of the spring. These leaf spring wedges are used to adjust pinion angle on vehicles equipped with rear leaf springs.
The wedge is mounted between the spring mount pad and the leaf spring itself. Doing so changes the angle the axle housing sits at. These bolt-on slapper bars from Competition Engineering are typical and affordable. They are easy to install and can be used to adjust suspension preload while stiffening the front half of the spring. This is my former Olds Omega drag car. This is Dan Zrust in a Plymouth Barracuda.
The car competes in the notoriously tough Super Stock ranks and is powered by the venerable ci Chrysler Hemi engine. Nationals in Indianapolis, Indiana. Chrysler muscle cars have the option of Mopar super stock springs.
They have a heavier spring rate on the passenger side than on the driver side, thus creating preload. Additionally, they are much stiffer in the front half of the spring due to the axle not being centered on the spring than the rear half, creating a rear suspension that works like a ladder bar setup.
I always liked to see the Chrysler Super Stock cars leave the starting line. You could tell how good they were, planting the rear tires, by the amount of separation visible between the leaves in the back half of the springs. Eventually, spring clamps were used to eliminate this separation and to create even better foot times, as the lesser amounts of separation caused the tire to be pushed into the pavement quicker. The Mopar super stock spring name came from the fact they were developed in the late s by Chrysler for its NHRA Super Stock race cars to give them maximum traction with minimum research and an advantage over the GM and Ford Super Stock cars of the time.
Some of the more notable Chrysler Super Stock racers were the Mancini brothers, who produced a string of successful Chrysler factory-backed race cars. Mancini Racing used that race experience to grow into a parts business that sells suspension parts for Chrysler race cars. Whether you are using Chry-ler super stock springs or not, the ride height can be controlled by re-arching the existing leaf springs.
Most large cities still have businesses that re-arch springs for truck or trailer applications, and should be able to do your car springs. Should the rear suspension rise or squat upon launch? The location of the front mount height in the chassis of the rear-end leaf spring deter-mines whether the car lifts in the rear or squats in the rear when leaving the starting line. If the mount is above the neutral line, the chassis lifts in the rear.
If the mount is below the neutral line, the chassis squats in the rear. I have tried to drive the point home that a car which lifts in the rear will plant the rear tires harder.
This is true to a point. You first must understand the basics. However, there is a point in horse-power-to-weight ratio that some cars with higher horsepower levels to 1, need the front of the leaf spring mount to be lowered.
Thirty years ago most full-bodied cars benefitted from a higher front leaf spring mount. Using the drawing on page 18 the fact of whether the car lifts or squats in the rear depends upon where the front spring mount is in relation to the neutral line.
Lower-horsepower cars can use a higher mount thus making the car lift in the rear upon launch. As horse-power levels to 1, increase, the mount needs to be lowered. The reason for the necessary lower mount is high-speed stability. A car lifting in the rear plants the tires harder but with that same lift at the top end it loses traction.
Now as the horse-power gets higher and higher more than 1, the car hasthe ability to break the tires loose on the top end. For safety and to be able to complete the run the front spring mount needs to be lowered. However the opposite occurs at the starting line. Most 1,plus-hp cars today have some sort of power adder NOS, blower, supercharger and can adjust the starting line power to compensate.
There is no exact measurement. The idea here is to experiment. As long as you have the knowledge, you can make it work through trial and error. Put that same no-hop bar on a Mustang also a factory 4-link suspension with the same horsepower-to-weight ratio and it will hook for about 6 inches and then blow the tires off.
The Mustang has the engine much closer to the rear end than the GM intermediate thus giving the rear control arms a completely different leverage affect. In fact they will either raise the rear of the lower control arm or if permitted lower the front of the lower control arm to almost level and leave the upper control arm in its factory location different class rules allow different modifications.
For high-speed acceleration, the intersection point needs to be much further out in the car for top-end stability. A car that lifts in the rear will hit the rear tire harder. You can hit the rear tire too hard and go into tire spin or tire shake.
There sometimes needs to be a compromise. Less hit at the starting line where power can be brought in slowly for more traction at the far end so the car can develop more miles per hour and still go straight. Keep in mind that if a car is lifting in the rear and the front is not lifting, the car is actually transferring weight to the front reverse pitch rotation and removing weight from the rear tires and having less possible traction.
The front mount needs to be even lower for top end traction, which causes a loss of traction at the starting line. Timers add the nitrous in stages with each stage farther down track. There is only one stage or no nitrous at the starting line. Just as 1, hp is an arbitrary point at which a car can turn left instead of turning right at the starting launch, it can also be used as an arbitrary point that a car needs the front leaf spring mount much lower in the chassis.
The neutral line is a reference point used when considering weight transfer pitch rotation in suspended cars. It begins at a point above the front spindle centerline as high off the ground as the center of gravity of your car, and continues to the rear tire contact patch directly below the rear axle centerline. If the front mount of the rear-end leaf spring is above the neutral line, the rear of the car raises upon launch.
Chapters 3 and 4 explain how to get the pivot point farther rearward in the car. The opposite is true with most rear-wheel-drive cars with leaf springs if the car is making a lot of horsepower, as they already have a pivot point too far rearward. The closer the front mount of the rear-end leaf spring is to the rear axle, the harder the suspension hits the rear tires of course, you can overpower a tire. If this same front mount of the rear-end leaf spring is below the neutral line, the car squats upon launch.
A car that lifts in the rear pushes down harder on the rear tires. However, moving the front mount of the rear-end leaf spring too close to the rear end causes the car to hit the tire too hard.
Too hard of a hit on the tires may work some of the time at some tracks but not all of the time at all tracks. The adjustable pinion snubber limits how far the rear axle housing is allowed to rotate. These are popular with Chrysler racers and this one is available from the Mopar experts at Mancini Racing. For the Chrysler cars, Mancini Racing is now offering an adjustable pinion snubber. This unit fits to the center front of the rear axle housing.
It helps control axle wind-up by adjusting the height of this snubber to the floorpan, depending on the individual requirement. This provides a more precise adjustment and locking than any other snubber on the market today. Snubber height is obtained by turning the threaded shaft up or down. When the bumper is at the desired height, it is locked in place by screwing the lock nut down tightly onto the tube top. This unit is CNC-machined to ensure manufacturing consistency and quality throughout.
If you could lift a car off the ground at its center of gravity the car would not roll in any direction—neither sideways nor front to rear. Center of gravity calculation is a very complicated and mathematical procedure. Solid spacers must replace the shocks. Two inch-tall blocks and a set of scales are also needed. First weigh the front of the car, then lift the rear of the car 10 inches by setting the scales on the inch blocks and reweigh the front of the car.
Then plug all of this information into a mathematical formula. Instead, use the camshaft centerline as the center of gravity when figuring the neutral line.
While not as accurate, it serves to use in calculating the neutral line for reference to see if the car will rise or squat. Having the exact center of gravity is not important, understanding the principals involved in this discussion is. No two cars respond the same with the same settings. One front leaf spring mounting point that works the best in a certain car may be completely wrong for a another car. Do your homework and determine what is best for your car. Ladder bars are a great asset to making a rear-wheel-drive car with leaf springs work.
This is because they relocate the pivot point farther forward in the car by having a lower mounting point than the front mount of the rear-end leaf spring, therefore making the mounting point closer to the neutral line. You can also lower the pivot point by lowering the front of the spring mount hole in the frame. This Advanced Chassis ladder- bar setup has double adjusters for setting pinion angle and suspension preload.
Ladder-bar setups are great on the drag strip, but not so great on the street. They tie the control arms together, which is fine for straight-line acceleration but detrimental to cornering. Most rear-wheel-driven cars with leaf springs are unibody designs with subframes. Instead, the frame and body are assembled as a single unit. The front subframe engine bay is connected to the floorpan as is the rear sub-frame rear suspension area.
These subframe connectors are typical for a unibody car and were designed for use under a Chrysler product. Subframe connectors tie the front and rear of the car together to make it stronger and less likely to flex. They are equally popular with drag enthusiasts and corner carvers. These unibody designs proved to be adequate for production car use and cost less to mass produce.
They typically result in a lighter-weight car, so fuel economy concerns were addressed as well. To correct this, subframe connectors that connect the front subframe rails with the rear subframe rails should be installed. This greatly stiffens the car and helps reduce body twist, making the car respond better to hard-launch conditions. These handy prefabricated connector packages let you tie the front and rear subframe longitudinally. Most frame connectors can be bolted or welded in, depending on individual preference and the design of the connector.
When installing your roll bar or roll cage, be sure to tie the front subframe, rear subframe, and subframe connectors all together.
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