NO supports needed.
Best detail in 0.1 resolution (obvious...)
tracks have to be printed with flexibel material (TPU)
axlecaps also best in TPU
1) Glue upper part to lower part, (the initial side of the lower part facing down, the rounded side facing front)
Be sure to align the parts properly!
2) Make 4 wheels, each wheel consisting of two halves (the halves are different and should snap together, if not, glue them)
3) Cut 2 axles/shafts from your 3mm round material, front 55mm long, rear axle 62mm long
4) Insert the axles in the holes, put a spacer (part of the wheelset) on each end, then the wheels
5) Stick endcaps on both ends of the front axle (glue them if they are not sitting tight!)
Check if wheels turn free and easy
6) Put a spacer on the rear axle wheels, then both side arms and the endcaps
7) Put the (rubber) tracks on the carriage, check for easy moving/turning
8) Stick/glue the shield to the front ends of the arms. Aling it properly parallel!
9) Insert the two headlights, the airfilter and the muffler to the body
10) Enjoy your toy!