Can you damage your axle with rear split wishbones? I heard that somewhere, same thing with a tube front axle(opposed to a beam front). I want to run front and rear split bones and quarter elipticals with a shop-fabbed adjuster similar to Posies but not cost $300(!). Brewsir said he only got 1-2 inches adjustment, I want more.
you probably wouldnt damage the axle, but the theory is that something else would break. If the split bones are solidly attached to the rear axle, and the bones run parallel to your frame, when you hit a bump on one side the axle is gonna want to twist. Most likely a tube is not gonna twist, so something else will have to give a little be it a weld or the bones themselves. If the bones come together under the car (like how they originally were) you have a lot more room to roll. I would imagine that the longer the split bones are, the less of a problem this would be. Now, this is all theory and geometry, many cars have been built this way and show no signs of failure, I'm just telling you what I heard.
In theory you will end up with the same problem. The rod end still will not twist the way it needs to, to compensate for the bones being solid to the axle. However, once again I see cars in magazines with this set up all the time, and these are cars that are driven regularly.
Riding down smooth road ,fine, in turning car will roll, at this time bones will act same as a sway bar, solid round tube rear axle will not give so all twist will be tranfered to bones,brackets or bone ends. The best way is to locate them is as close to the middle of chassis in a trangliar form as possible..
I mounted mine outside. I knew the negatives, but I did it anyway because that's what I wanted. All the "roll" flex has to come from the frontend and the rear spring take's up some I assume. Also the stock wishbone ball rubber must help. Haven't got a ton of miles on it yet, maybe 500, but so far no problems. I figured off road traction would suffer from lightening of rear wheel one side or other due to stiffness. No problems, not stuck in the woods yet. I won't do it next time, if I can the next one will keep the bones on the tube, and frame straight, more speedster. But then the gas tank will be a problem... It is NOT what an engineer would recommend, but this one doesn't need a sway bar. http://www.directimagehost.com/is.php?i=106803&img=DSC02623.JPG http://www.directimagehost.com/is.php?i=112943&img=5988DSC02571.JPG http://www.directimagehost.com/is.php?i=115059&img=DSC02786.JPG
I did one lots of years ago using 3/4 ton tierod ends for the pivot points. This 32 roadster is still running with lots of miles and I think the same suspension.
If you are using an early Ford rear axle, stock spring and torque tube spliting rear wishbones accomplishes nothing . However if you are locating an open drive rear and are making up a set of wishbones to locate the rear axle, the only wishbones that are heavy enough would be the 35/36 Ford design and these will even bow under serious stress. If you are attempting to use the factory 37-48 style they have nowhere near heavy enough sidewall thickness for radius rod use and are easily stressed and bend, therefore should not be used. Front wishbones are of adequate thickness so spliting does not to pose a problem. When making your own the following is for consideration. When discussing radius rod twist and body roll, the majority of the body roll is during cornering and is probably only in the area of 1 " with 2" as maximum. The biggest problem is the torsional twist place on the suspension when going over surfaces at an angle such as driveway or parking lot curb cuts. This places a twist on the arms, greater than during normal diving, and the locating position on the frame has to be considered. Torsional twist is addressed by the installation of some type of swivel end or positioning the rear locating bars closer to the centerline of the car to minimise rotational angle. If you choose to locate the radius rod further from the centerline they will encounter more of a twist. In choosing a radius rod design to elimimnate radius rod twist there are a number of options. Urethane bushings, spherical ball ends or tie rod ends are all used for pivots. The urethane bushings give the least torsional movement so therefore should be avoided for large angle deflection. Spherical ball ends (heim) work ok as they have enough axial movement, but have to be continually lubricated. The best, although not as pretty, are tie rod ends. They unfortunately dont look as neat but they have the ability to generate a larger rotational angle and therefore eliminate twist on the rods. The larger size truck tie rod ends work better for radius rod application. I know that there are all kinds of setups out there being marketed or pictured in magazines, some just work better than others. As for damaging your axle, doubtful. Over 2" of suspension travel on most road vehicles is like riding in a boat on a rough sea. While you need 3-4" between the axle and frame for clearence safety, most cars ride down the road with 3/4" to 1 1/2" travel on compression.
Folks been doin' it for 50 years or so. The thing you got to remember is that you don't have the suspension travel of a rock crawler or a desert racer its a rod. You run onto the same problem with a set of ladder bars, what will normally happen is that it won't really travel enough to make much difference and in a real bind given that everything is built sturdy it will lift one wheel so if you got an open rear and don't have enough enertia to carry you over the hump you're there. Something that will help is to get the front anchor/pivot point somewhere close to the center of the front u joint. The longer you make your suspension links the better off you are, longer links swing smoother arcs. But as already said you don't have tons of suspension travel so you don't have that much to worry about.
The Jalopy Journal
