Advice on new tires & spacers

So then SPC's can do this since the ball joint position is adjustable, correct?

I thought JBA's ball joints were also adjustable but they are not.

 

The adjustability of SPCs upper ball joint doesn’t change the fact that, if you want increased caster angle after a lift, you have to relocate/adjust the position of the upper ball joint rearward. I should clarify, before I said the Lower control arm’s ball joint is fixed. That’s actually not true since that’s what the eccentrics are for, but they don’t move the lower ball joint forward enough to guarantee you can get caster within spec after a lift with stock UCAs).

You could theoretically adjust the SPCs ball joint to be in the same place as it is in a stock UCA to keep the tire from rubbing on the body mount, but that would defeat the purpose of getting an after market UCA (to be able to get good caster angles).

Really, the only reason to get any aftermarket UCA is to ensure that your caster angles can stay within factory spec (at least for lifts that aren’t long travel).

But, as mentioned earlier, because the only way to create a higher caster angle is to move the position of the upper balljoint rearward, the overall tire gets moved rearward as well, reducing tire clearance to the body mount.

I have about 2.5in lift, and I decided to keep the stock UCAs. I have no rubbing under full articulation and wheel turn with 285/70-17 K02s. However, this meant that I couldn’t get caster within factory specs. Which isn’t a big deal since it’s pretty close anyway, and I like the spicy steering feel lol.

eta: after thinking about the SPC adjustable ball joint design, I really wonder if it’s a answer looking for a problem. There’s really no reason for it as far as I can tell. Especially because if you wanted higher caster, an aftermarket UCA with a ball joint that is fixed (but relocated further rearward) still allows for a fair amount of increased caster, by using the eccentrics on the lower control arm. Maybe somebody that’s chopped the body mounts wants an extreme amount of caster to justify the the SPCs, but you have to wonder if that’s worth risking the real possibility of frequent ball joint failures experienced with SPCs.

eta number 2: I have to admit that it took me a couple of Tinkerer videos to understand the interplay of all this, so I might be explaining this in an overcomplicated way. But in summary, if you want to reduce possibility/severity of rubbing on the body mount, keep the stock UCAs. But this will be at the expense of caster angle.

 

Can you explain that please? I thought the eccentrics adjust camber by moving the lower control arm (and thus the lower ball joint) towards or away from the centerline of the vehicle. How does eccentrics adjustment affect caster?

 

In an extreme example, if the front adjuster is positioned to pull the front arm of the UCA in towards vehicle centerline, and the rear adjuster to push the rear arm away from the centerline, the lower ball joint will end up moving forward relative to the UCA ball joint.

In reality though, you probably can’t go to that extreme because you may not be able to maintain appropriate toe or camber numbers. But in my case, they were able to get really close to those extremes and still keep other angles in spec.

 

So are you sacrificing camber for the sake of caster?