On #58 I just put some J&M rear uppers and lowers. They have a 3 piece bushing. The center is like a ball and the outer 2 are cups so it pivots and does not bind! They are also a sponsor on Stangnet. You can also get them in Red powdercoat for the same price.
I have a Griggs HD torque arm with no uppers on one of my cars, and yeah it works great but not every one has the money for that.
On the lowers I got the ones with the spherical on the axle end and the 3 piece poly ball bushings on the chassis end.
Check out the link on the degrees of rotation how on a 2 piece poly bushing it would snap the bolt from binding but with the J&M is only applied 42 ft lbs of torque on the bolt. (They show this on the lower arm link, so I posted it first)
Here is shows the lower arms,
Rear Lower Control Arms
Here are the uppers
1979-2004 Mustang Street Upper Control Arm (patent pending poly-ball bushings)
"We built a fixture which simulated a factory control arm mounting and tested how much force was needed to make the control arm articulate (twist) in those mounts and the results where astounding.
Poly-Ball Bushings:
5 degrees of total rotation = 26.1 foot/pounds of torque
7.5 degrees of total rotation = 35.8 foot/pounds of torque
10 degrees of total rotation = 41.7 foot/pounds of torque
Standard 2 piece setup using only 85 durometer bushings:
5 degrees of total rotation = 124.7 foot/pounds of torque
7.5 degrees of total rotation = 156.4 foot/pounds of torque
10 degrees of total rotation = not measurable with fixture. The 1/2" grade 8 bolt twisted in half at 9.2 degrees which was 210 foot/pounds of torque.
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