dmcurry22 said:
Where is the pivot point on a solid axle. Is it the opposite wheel or the center of the transverse spring or some other point. My concern is the spring weight for the split axle configuration. If the pivot on a solid axle is in the middle of the transverse spring I will be OK in sizing my coil overs, but if the pivot point is the opposite wheel I think I am going to have to go with a much lighter spring weight to get the same ride. Any thoughts on this guys?
Typically on a solid axle system, there is a tie-rod connecting the right and left steering arms, so there is no bump steer induced there. Where the problem lies is the drag link that connects the steering gear (typically on the left frame rail) to the steering arm on the right. It is the length of the drag link that will determine how much bump steer will be introduced when the suspension moves into bump or droop. The longer the drag link the better typically.
As to spring rate selection, the critical dimension is the distance from the tire centerline to the lower shock mount on the axle. The longer the distance, the more leverage on the spring, (from the tire/wheel assembly) the stiffer the spring needs to be. The distance from the lower shock mount to the inner split axle pivot will not be a factor.
Overall, the longer the split axle, the less camber change you will get. With the small amount (relatively speaking) of suspension travel that is typical for a low hot rod, it should be manageable, even with a pivot in the middle. When a vehicle is turning, the outboard suspension compresses causing the tire/wheel assembly to go toward negative camber. That is a good thing. The inboard going positive is not so bad as it is much less loaded. Ford had it right by designing the beams as long as possible. Keep in mind that the inboard pivot point height location is critical so when you are at final ride height, the base camber setting is correct. Any ride height adjustments will affect your camber setting, and it isn't adjustable other than by ride height changes unless you make the inner pivot location adjustable or bend the axle.
Andy