This is a wheel that I designed for my JJRC LT832. The weight of two of these wheels and tires is about the same weight as one stock wheel and tire. They are about the same height as the stock tires (see pictures). These are great for speed runs, but the truck steers terribly with them because they are only 4mm wide. If you are driving on a tight track, stick with the stock tires or something similar.
Two 2x5x2.5mm bearings (one for each wheel).
Two Lego tires for the 4185 pulley wheel (see last picture). Search "lego pulley tire" and they should show up (or steal from your kids' Lego collection :-).
Print it with the flat side facing up (the side the bearing goes in). I tried using less infill, but because the spokes are so thin it made no difference.