Landing gear are tricky to clean and maintain.  While they get plenty dirty, there are often sensitive, expensive electronics and seals affixed to them that make the use of harmful solvents a long term risk.  Certified by Boeing to their D6-17487 standard, commercial airlines use Grime Off for the same reason you should. Mean, green, and made to clean, Grime-Off Aircraft Cleaner and Degreaser safely removes dirt, grit, and grease from struts without harming critical components over time.