Holy cow I am so jealous right now! You have done everything I want done to my Sub. You must have spacers for your trail boss wheels?
Correct! - FRONT wheel spacers became
necessary with the 18" Trail Boss'.
I needed an additional 1/4" of backspacing to clear the outer tie rod end after moving to the 18's from the OE 20" wheels (
20's cleared without the need of wheel spacers).
I have installed
1/2" hub centric spacers up front; however, RC does offer a 1/4" spacer, but not hub centric.
The BDS Suspension lifts for our GMs increase the front track width by 1.5"/side; I think primarily due to the new knuckle and tie rod extension from the drop lift design.
To get the rear to line up a bit more with the front track, I have
1.5" rear hub centric spacers installed as well. The Trail Boss wheels have a nice little pocket design on the inside that allows for the 1.5" spacer and lugs -> no cutting of the OE wheel hub bolt was required. I have read that any spacer less than 1.75" would require the bolt to be trimmed...
So far, no problems on or off road with the spacers. I have been trying to rotate the tires every 2500-4000 miles and checking the wheel spacers at the same time.
About 15k miles now with the BDS 4" lift and absolutely no complaints except that I've learned to carry a small step stool on our family adventures. Accessing the roof cargo (ie: kayaks) is MUCH safer with a little help to stand on.