Positive versus Negative Caster

So, I have SPC upper control arms that are adjustable (see SPC adjust sheet). From my understanding, adding positive (+) caster should push the wheels forward to help prevent rubbing against the the rear inner fender and/or rear body mount. I was originally set at position D and was only slightly rubbing at full lock and the suspension compressed. Just moved it to position A and now am rubbing the rear even worse. I haven’t taken it in for an alignment yet but am wondering what I did wrong?

 

I’d get the alignment done first and see what they get. If you set correctly getting 3-4 degrees caster should be easy. Personally that’s why I went with JBA cause the caster is built in no messing with that adjustment like you have.

 

Took it to the alignment shop, with the sheet above and let them do their thing. Looks like the passenger side was set to position C and the drivers side was set to position D. And they adjusted everything else the rest of the suspension would allow to push the wheels forward as much as they could without messing up the camber. Going to run it and see how it goes. Will still need to do some slight trimming in the rear fender well to prevent rubbing in specific scenarios.

 

It's important to remember that with the SPC UCAs, increasing the castor using the adjustment on the arm actually decreases clearance between the tire and the rear of the wheel well. This is opposite of what happens when you increase castor using the LCA adjusters. If you're after max clearance at the rear of the wheel well, your best bet is to max out the caster (for max clearance) on the LCA, then use the SPC arms to get the camber and caster into spec.

 

Op, if you moved it to 'A' you moved it all the way back into the rear/cab mount.
You would want to move it to the 'G' setting to move it all the way forward, into the front fender.

 

Well that’s counter intuitive. Since when you add positive via the cams you’re moving the top of the axis back and the bottom forward. I can see why so many guys mess that up.

 

Thanks everyone. It was definitely confusing me at first. But, think we got it figured out now. Caster maxed out for clearance while keeping camber in spec. Now it’s time to do some trimming.