Help on shims

A newbie on this subject, but I have put Bilstein's 5100 all the way around and on front they are on the top setting. I have noticed that a lot of guys are saying they put 2 shims on the drivers side and 1 on the passengers side if you do the leveling with the 5100's. My questions is why is this needed? I'm just not sure what that does? thanks for any input on this.

 

The top setting is for 2.5 inches. Adding 1, 1/4" shim provides a 1/2 inch of lift, giving a full 3 inches. Adding the 2nd shim on the driver side is to account for the "Tundra Lean" generally caused due to the fuel tank being on that side.

 

It seems to vary from truck to truck. Some have a noticeable lean on the left front. some don't. I ended up with 5100s on the top setting and 2 shims on each side. Then I brought the back up with +2 shackles. Sits level, rides great and fits 35s.