fortydegnorth wrote:
I'm trying to wrap my head around this. The beam is just two straight tubes that the arms fit in. The only thing that changes is the steering if you go wider. With a center mount rack I can't really see how the tire would lean any differently at whatever beam width you have. The suspension will cycle the exact same even if the beam was 400' wide. The steering will obviously change, but with a rack and pinion you should be able to experiment with travel and rack location to adjust most of the bump steer out. I'd be more worried about the extra length of the arms moving the wheel location further back on the frame. Frames typically widen out as they go back, so on a stock width beam it may create a rubbing issue with the back of the tire and frame. I can't see how the geometry, other than steering, would be effected though.
It can't. (period) Where the problem comes in with the +4" arm is,
they can't be used with torsion springs. I'm not aware of one commercial builder in the US that builds a +4" arm that has the provision for torsion springs. The springs can not handle the amount of twist a +4" arm will put them through and the springs will fail in short order if they could be used. As far as the width of the beam, it has no affect on steering geometry the only thing it will affect is the overall travel of the arm because of tie rod interference with the frame. I have +4" arms and a 4" wider beam on my Funco project. This set up gives me 14" of wheel travel, if I were to have used a 6" wider beam it would of had just under 16" of travel.
Also worth noting, on the stock link/pin set up and the higher end after market builders (mine included) the tires do "lean" in a turn. The king pin is on a 3.5 deg angle and the spindle stub is welded to the knuckle on a 3.5 deg angle which makes the tire lean on a turn.