Seeing that a lot of rodders are building there own rear end setups, can some knowledgeable person give us the basics on Ladder Bars? Stuff like distance B/W mounting points on the axle, Angle of the top and bottom bars relative to the ground, where to mount the front of the bars - relative to the gearbox, and the chassis etc etc
Definatly, I need to build some for my A and was wondering how you figure the correct length? And if the it can follow the inside of the frame rail and still be stable in the corners? -Jesse
Good idea- rear trac bar installation would be another helpful one; I ordered a set that didn't come with instructions, and dumb as it may sound I can't figure it out on my own. Really dig the ladder bar idea.
firstly: I AM NO EXPERT!! i'm merely going to mention a few nuggets that i THINK i know to get the ball rolling... also, all my comments are aimed at driving the street, nothing to do with good launch control at the drags... ladder bars are not a fantastic setup for the street, the main reason being their inability to twist from one side to the other. in a sense, they are their own anti-roll bar. for this reason, at the nose of the bars you need a big, compliant bush if you're planning on taking corners or potholes with any regularity, or your bars will break. as for length, the longer the better. as the ladder bars are basically just a lever, your rear axle traces an arc as it passes through its travel. the greater the radius of the arc, the more compliant your suspension will be. the ultimate ladder bar would attach to the car five blocks in front, but this is somewhat difficult from a packaging perspective, which is why most mount off somewhere near the gearbox X-member. it's a convenient place to hang 'em. true ladder bars, say like this: ...don't have a panhard bar because they are totally bound to each other by the big X in the center, so they can't drift sideways. imagine that same setup WITHOUT the big X. the whole axle could sway side to side by turning the square into a parallelogram. to combat this, you can either angle your ladder bars in (when viewed from above) so the shape they draw is a rhombus, not a square, or you can add a panhard bar which is usually used on a four link setup (which i'd encourage you to look at from a handling perspective anyway... though the geometry can be a bitch to get right without the aid of CAD). angles? generally i think most people run the upper bar about 5 to 7 degrees up, though again this comes down to packaging partly, but also so the axle is pushing *almost* parallel with the arc traced by the end of the ladder bars. make sense? perhaps someone with a little more experience than me can shed a little more light...
The ideal length is actually even with the front U-joint. This allows the driveshaft and ladder bars to work together and swing the same arc. No binding. Just FYI.
FWIW: this length discussion is one of the main reasons to run a 4 link (race car type, not OEM). You can set the bars up to where they would intersect ANYWHERE, even way out in front of the car, if they were long enough, but all in a nice compact little package! (try to visualize a long straight line running out the front of the upper and lower bars)
My experience is with race cars only so remember this. Ladder bars are usually 32-34 inchs long.The reason is the floorboard gets in the way ,very much so if your car is low.The front ladder bar crossmember on a race car is close to where the main roll cage attaches so to help spread the load. I set a ladder bar up with the lower bar parrallel to the ground. I also have adjustment holes both up and down. Raising the front of the bar provides more traction ,lowering less.Unfortunatly in order to adjust up and down you also have to adjust pinion angle.Cheap or anyway most ladders ,because of the two different angles of the rear attachment points ,have only one place that the rear bolts will fit in the bracket .Some have another pivot built in the lower bar and at least one bends the upper bar to allow adjustment. A diagonal link is the easiest way to keep the rear straight . I use a U-shaped bracket that the rear ladder bar bolt ( lower) goes thru and then I attach the diagonal link to it. The same is done on the front on the opposite side.You can also weld a tab on the bar itself. I use 1 inch .156 wall tube and then direct thread it for 3/4 ends for the diagonal link. If you have the tap use a left on one side and a right on the other ,it makes adjustment easy. A yoke or wishbone is also a good way to keep the rear straight.It can be mounted below the rear end or above . I mount the two ends on the car and the single end on top of the rear end housing. But it will work either way. The secret is the single end mount is inserted into another snug fitting tube so it can slide in and out to prevent binding.,I use grease on mine. Hope this helps, OOPS my edit. I see no reason to run up the same as the front u-joint ,but the cars I work on have slip yoke but obviously if you have an enclosed driveline you must consider this
here's a sketch showing what I did, I located my front pivot on an imaginary line drawn between the contact patch of the rear tires and where I estimated the center of gravity of the car to be. reason being that if the front pivot is below this line, wieght is lifted off the front wheels and planted on the rears, some of this is good as you want traction at the drive wheels but, too much will lift the front wheels off the ground, it's hard to stear with your front wheels in the air all the time of course if the pivot point is above this line then the opposite would happen, the weight would transfer to the front wheels, lifting the rears and reducing traction, smokin' the hides is cool but you can't win races without traction. so I chose to place the pivot on the line in an attempt to have a nice straight launch without the rear squating or jacking too much. Paul