Lego plastic vs carbon fiber vs aluminium vs stainless steel. Lego-compatible axles tested comprehensively. Enjoy!

0:09 Max torque test
04:15 Durability test
05:56 Friction test 1: car and a slope
06:54 Friction test 2: rotating plate
07:51 Noise test
08:44 Insertion test into Lego parts
09:44 Close-up images
10:21 Weight & density comparison
10:53 Price comparison (Nov 2023)
11:14 RESULTS SUMMARY

Carbon fiber axles are made by CaDA Bricks.
CaDA Carbon Fiber Axles | JT7001*100

Aluminium axles are made by Metal Technic Parts a.k.a. Dark Ice Designs. They also make the metal gears and beams that were used in the max torque test bench.
Axles

The stainless steel axles were originally bought from Brick Machine Shop on BrickLink (now obsolete). As of Jan 2026, steel axles are available from MTP.
Stainless steel Metal Axle compatible with Lego Technic