By Coby Hughey
&
Matt Grow
The wristed radius arm is revolutionizing the Early Bronco front end. For that
matter, any Ford coil sprung straight axle front end. Simply put, the wristed
arm alleviates the bind inherent in stock Ford front ends.
Longer, extended radius arms will relieve this bind, but require new brackets, and you have to build two of them. Also, the longer they get, the more susceptible to bending they become.
The wristed arm (you only need one), is a completely bolt on design, using the stock brackets. How does it work? Simply put, a spherical bearing machined into the radius arm allows the front end to FLEX!
Only one? Yup, both authors have their respective arms mounted on the passenger side. The driverside is the stock arm, which controls caster. The arms are pinnable for street use, but even without pinning, side effects on the street are minimal.
Here we have two different designs. The
lower version in a solid piece of steel, machined from 4130 steel. Its cooresponding
"C" cup is on the upper right. The upper arm is pieced together from
tubing and stock steel. The authors are running the 4130 version. Pinning on
both versions are slightly different. The 4130 version uses two pins, top and
bottom. The other uses one pin the goes through the entire arm. 
Here is the 4130 arm, with the spherical bearing and spacers visible. The spacers are placed on the outer edges of the bearing and the inner "C" cup wall. This is due to twisting of the axle when fully flexed.
The 4130 is on the left. For the most complete
strength, make sure the bearing rides on the shank of the bolt. Having the threads
contact the bearing is a sure way for premature failure.
The results, well the pics speak for themselves:
This is Matt's 1977 Bronco, equipped with:
3.5" Wildhorses Rockcrawler coils
4.5" Wildhorses 11 leaf rear springs
Poly C bushings
Poly spring bushings
Rubber radius arm bushings.
This is Coby's Black Cloud, equipped with:
The new 4.5" BC Bronco coils (shown with Duff coils above)
3.5" Wildhorses 11 leaf rear springs
Poly C bushings
Poly spring bushings
Rubber radius arm bushings.